ANATOMY

A N A T O M Y.

ANATOMY is the art of dissecting the solid parts of animal bodies, with a view to discover their structure, connection, and uses.

ANATOMY is not only the basis of all medical knowledge, but is a very interesting object to the philosopher and natural historian.

In treating this useful subject, we shall divide it into the following parts: I. Of the BONES. II. Of the MUSCLES. III. Of the ARTERIES. IV. Of the VEINS. V. Of the NERVES. VI. Of such parts of the body as are not comprehended in any of the above, e. g. The BRAIN, THORAX, ABDOMEN, &c. &c.

P A R T I.

O F T H E B O N E S.

SECT. I. Of the BONES in general.

BEFORE we examine the structure of the bones, the periosteum, a membrane with which they are covered, must be described.

The periosteum can be divided into layers of fibres. The exterior ones, composed of the fibres of the muscles connected to the bones, vary in their number, size, and direction, and consequently occasion a very great difference in the thickness and strength of the periosteum of different bones. The internal layer is every where nearly of a similar structure, and has its fibres in the same direction with those of the bone to which they are contiguous.

Except where muscles, cartilages, or ligaments, are inserted into the periosteum, its external surface is connected to the surrounding parts by thin cellular membranes, which can easily be stretched considerably, but

shorten themselves whenever the stretching force is removed.

When the periosteum is torn off from bones, we see a great number of white threads produced from that membrane into them; and after a successful injection of the arteries with a red liquor, numerous vessels are not only seen on the periosteum, but most of the fibres sent from the membrane to the bone shew themselves to be vessels entering it, with the injected liquor in them; and when they are broken, by tearing off the periosteum, the surface of the bone is almost covered with red points.

The great sensibility of the periosteum in the deep-seated species of paronychia, in exostoses, nodi, tophi, and gummata, from a lues venerea, or whenever this membrane is in an inflamed state, is a sufficient proof that it is well provided with nerves; though they are perhaps too small to be traced.

The chief uses of the periosteum are: 1. To allow the muscles, when they contract or are stretched, to move

2. To keep in due order, and to support the vessels in their passage to the bones. 3. By being firmly braced on the bones, to assist in setting limits to their increase, and to check their overgrowth. 4. To strengthen the connection of the bones with their epiphyses, ligaments, and cartilages, which are easily separated in young creatures, when this membrane is taken away. 5. To afford convenient origin and insertion to several muscles which are fixed to this membrane. And, lastly, to warn us when any injury is offered to the parts it covers.

The BONES are the most hard and solid parts of the body, and generally of a white colour; only in a living creature they are bluish, which is owing to the blood in the small vessels under their surface.

Bones are composed of a great many plates, each of which is made up of fibres or strings united by smaller fibrils; which being irregularly disposed and interwoven with the other larger fibres, make a reticular work. This texture is plainly seen in the bones of foetuses, which have not their parts closely compacted, and in the bones of adults, which have been burnt, long exposed to the weather, or whose composition has been made loose by diseases.

The plates are said to be firmly joined to each other by a great number of clavicular, or small bony processes, which, rising from the inner plates, pierce through some, and are fixed into the more external ones.

Though the exterior part of bones is composed of firm compact plates, yet they are all more or less cavernous internally. In some, the solid sides are brought so near, that little cavity can be seen; and in others, the cavities are so large, that such bones are generally esteemed to be hollow or siltular. But the internal spongy texture is most evident in young animals.

This spongy, cavernous, internal part of bones, is generally called their cancelli or lattice-work.

The twisting and windings which these cancelli make, and the interstices which they leave, differ considerably in figure, number, and size; and therefore form little cells, which are as different, but communicate with each other.

The cancelli sustain the membranous bags of the marrow which are stretched upon them, and thereby hinder these membranous parts from being torn or removed out of their proper places, in the violent motions and different postures which the bones are employed in.

The depressions between the fibres of the external plates of bones appear like so many furrows on their surface, into each of which the periosteum enters.

Both on the ridges and furrows, numerous little pits or orifices of canals are to be seen, by which the vessels pass to and from the bones.

After a successful injection, the arteries can be traced in their course from the pits to the plates and fibres.

We may conclude, from arteries being accompanied with veins, so far as we can trace them in every other part of the body, that there are also veins in the bones.

The bones of a living animal are so insensible that they can be cut, rasped, or burnt, without putting the creature to pain, and the nerves distributed in their substance

cannot be shewn by dissection; from which it might be inferred, that they have no nerves distributed to them: But the general tenor of nature, which bestows nerves to all the other parts, should prevent our drawing such a conclusion.

The vascular texture of bones must make them subject to obstructions, ecchymoses, ulcers, gangrenes, and most other diseases which the softer parts are affected with; and therefore there may be a greater variety of caries than is commonly described.

On the internal surface of the solid parts of bones, there are orifices of canals, which pass outwards through the plates to open into other canals that are in a longitudinal direction, from which other transverse passages go out to terminate in other longitudinal canals; and this structure is continued through the whole substance of bones, both these kinds of canals becoming smaller gradually as they approach the outer surface.—These canals are to be seen to the best advantage in a bone burnt till it is white: When it is broken transversely, the orifices of the longitudinal canals are in view; and when we separate the plates, the transverse ones are to be observed.

Most bones have one or more large oblique canals formed through their sides for the passage of the medullary vessels.

The bones sustain and defend the other parts of the body.

Bones are lined within, as well as covered externally, with a membrane; which is therefore commonly called periosteum internum.

The internal periosteum is an extremely fine membrane; nay, frequently it has a loose reticular texture; and therefore it is compared by some to the arachnoide coat of the spinal marrow: so that we cannot expect to divide it into layers as we can divide the external periosteum. We can, however, observe its processes entering into the transverse pores of the bones, where probably they are continued to form the immediate canals for the marrow distributed through the substance of the bones; and along with them vessels are sent, as from the external periosteum, into the bone. These processes being of a very delicate texture, the adhesion of this membrane to the bone is so small, that it separates commonly more easily from the bone than from the marrow which it contains.

From the internal surface of the internal periosteum, a great number of thin membranes are produced; which, passing across the cavity, unite with others of the same kind, and form so many distinct bags, which communicate with each other; and these again are subdivided into communicating vesicular cells, in which the marrow is contained.

The MARROW is the oily part of the blood, separated by small arteries, and deposited in these cells. Its colour and consistence may therefore vary according to the state of the vessels, and their distribution on the membranes of the cells.

Besides the arteries already mentioned as being sent from the bones to the marrow, there is at least one artery for each bone; several bones have more, whose principal use is to convey and secrete this oily matter.

The

The blood, which remains after the secretion of the marrow, is returned by proper veins, which are collected from the membranes into one or two large trunks, to pass out at the same holes at which the arteries enter.

The vessels of the marrow, wrapt up in one common coat from the periosteum, pass through the bones by proper canals; the most considerable of which are about the middle of each bone, and are very oblique.

From the structure of the contents of the bones, we may judge how these parts, as well as others, may be subject to oedema, phlegmon, erysipelas, scirrhus, &c. and may thence be led to a cure of each, before the common consequence, putrefaction, takes place, and frequently occasions the loss of the limb, if not of the patient.

The marrow is of very considerable use to the bones; for by entering their transverse canals, and passing from them into the longitudinal ones, it is communicated to all the plates, to soften and connect their fibres, whereby they are preserved from becoming too brittle.

When the marrow, after having served the uses mentioned, is reabsorbed into the mass of blood, it corrects the too great acrimony communicated to the saline particles of our fluids by their circulation and heat; in the same manner as lixivial salts are blunted by oil in making soap.

Since it is the nature of all oil to become thin and rancid when exposed long to heat, and bones have much oil in their firm hard substance, we may know why an ungrateful smell, and dark-coloured thin ichor, proceed more from corrupted bones than from other parts of the body; and we can understand the reason of the changes of colour which bones undergo, according to their different degrees of mortification.

Though bones so far agree in their structure and annexed parts, yet we may observe a considerable difference among them in their magnitude, figure, situation, substance, connection, uses, &c. Of these we shall only mention two, viz. that some bones are broad and flat, while others are long and round.

The broad bones have thin sides, by the plates being soon and equally sent off to form the lattice-work; which therefore is thicker, and nearly of an equal form all through. By this structure, they are well adapted to their uses, of affording a large enough surface for the muscles to rise from, and move upon, and of defending sufficiently the parts which they inclose.

The round bones have thick strong walls in the middle, and become very thin towards their ends, which is owing to very few plates separating at their middle; where, on that account, the canelli are so fine and small that they are not taken notice of: But such bones are said to have a large reservoir of oil in this place. Towards their ends the lattice-work becomes very thick, and rather more complete than in the other sort of bones.—These round bones having strong forces naturally applied to them, and being otherwise exposed to violent injuries, have need of a cylindrical figure to resist external pressure, and of a considerable quantity of oil to preserve them from becoming too brittle. Besides which, they are advantageously provided with thick sides towards their middle, where the greatest forces are applied to injure

them; while their hollowness increases their diameter, and consequently their strength, to resist forces applied to break them transversely.

Many bones have protuberances, or processes, rising out from them. If a process stands out in a roundish ball, it is called caput, or head.—If the head is flattened, it obtains the appellation of condyle.—A rough unequal protuberance is called tuberosity.—When a process rises narrow, and then becomes large, the narrow or small part is named cervix, or neck.—Long ridges of bones are called spines.—Such processes as terminate in a sharp point, have the general name of corona, or coronoid, bellowed on them, though most of them receive particular names from the resemblance they have, or are imagined to have, to other substances, e. g. mastoid, styloid, &c.—Such processes as form brims of cavities, are called supercilia.

Processes serve for the advantageous origin and insertion of muscles, and render the articulations firm and stable.

In children these processes are real epiphyses, or distinct bones, which are afterwards united to the other parts; such are the styloid processes of the temporal bones, processes of the vertebrae, trochanters of the thigh, &c.

On the surfaces of a great many of the bones there are cavities, or depressions: If these are deep, with large brims, authors name them cotyla; if they are superficial, they obtain the designation of glenæ, or glenoid. These general classes are again divided into several species:—Of which pits are small roundish channels sunk perpendicularly into the bone;—furrows are long narrow canals, formed in the surface;—notches or notches, small breaches in the bone;—sinuities, broad, but superficial depressions without brims;—fissæ, large deep cavities, which are not equally surrounded by high brims;—sinuses, large cavities within the substance of the bones, with small apertures;—foramina, or holes, canals that pierce quite through the substance of the bones.—When this last sort of cavity is extended any long way within a bone, the middle part retains the name of canal, and its ends are called holes.

The cavities allow the heads of bones to play in them; they lodge and defend other parts; they afford safe passage to vessels, muscles, &c.

To far the greater number of bones, whose ends are not joined to other bones by an immovable articulation, there are smaller ones annexed, which afterwards become scarce distinguishable from the substance of the bone itself. These are called epiphyses, or appendices. Some bones have one, others have two, three, or four of these appendices annexed by the means of cartilages, which are of a considerable thickness in children, but by age become thinner.

Several processes (e. g. trochanters of the thigh, spine of the scapula, &c.) have epiphyses; and processes frequently rise out from epiphyses; for example, at the lower end of the femur, ulna, tibia, &c.

The epiphyses are united chiefly to such bones as are destined for frequent and violent motion; and for this purpose they are wisely framed of a larger diameter than the

the bone they belong to; for by this means, the surface of contact between the two bones of any articulation being increased, their conjunction becomes firmer, and the muscles inserted into them act with greater force, by reason of their axes being further removed from the center of motion.

The softness of the ends of bones may be of some advantage in the womb, and at birth, after which the ossification begins at different points to form epiphyses, before the ossification can extend from the middle to the ends of the bones.

However solid and compact adult bones are, yet they were once cartilages, membranes, nay, a mere jelly. This needs no further proof, than repeated observations of embryos when dissected: And how much more tender must the bones be before that time, when neither knife nor eye is capable to discover the least rudiments of them? By degrees they become more solid, then assume the nature of gristles, and at last ossify; the cohesion of their plates and fibres always increasing in proportion to their increased solidities; as is evident from the time necessary to unravel the texture of bones of people of different ages, or of dense and of spongy bones, or of the different parts of the same bone, and from the more tedious exfoliations of the bones of adults than of children.

The ossification of bones depends principally on their vessels being so disposed, and of such diameters, as to separate a liquor, which may easily turn into a bony substance, when it is deprived of its thinner parts; as seems plain from the observation of the callous matter separated after fractures and ulcers, where part of the bone is taken out: For in these cases, the vessels extending themselves, and the liquors added to them, are gradually formed into granulated flesh; which fills up all the space where the bone is taken from, then hardens, till it becomes as firm as any other part of the bone. This happens frequently, even when the ends of the diseased bone are at a considerable distance from each other.

The induration of bones is also greatly assisted by their being exposed, more than any other parts, to the strong pressure of the great weights they support, to the violent contraction of the muscles fixed to them, and to the force of the parts they contain, which endeavour to make way for their own further growth. By all this pressing force, the solid fibres and vessels of bones are thrust closer; and such particles of the fluids conveyed in these vessels as are fit to be united to the fibres, are sooner and more firmly incorporated with them, while the remaining fluids are forcibly driven out by the veins, to be mixed with the mass of blood. In consequence of this, the vessels gradually diminish as the bones harden. From which again we can understand one reason, why the bones of young animals sooner re-unite after a fracture than those of old; and why cattle that are put too soon to hard labour, seldom are of such large size as others of the same brood, who are longer kept from labour.

From the effects of pressure only it is, that we can account for the bones of old people having their sides

much thinner, yet more dense and solid, while the cavities are much larger than in those of young people; and for the prints of muscles, vessels, &c. being so much more strongly marked on the surfaces of the former than of the latter, if they belong to people of near the same condition in life.—Pressure must likewise be the cause, which, in people of equal ages, makes these prints stronger in the bones of those who had much labour and exercise, than they are in people who have led an indolent unactive life.

Having thus considered the bones when single, we shall next shew the different manner of their conjunctions. To express these, anatomists have contrived a great number of technical terms; about the meaning, propriety, and classing of which, there has been a variety of opinions. Some of these terms it is necessary to retain, since they serve to express the various circumstances of the articulations, and to understand the writers on this subject.

The ARTICULATIONS are most commonly divided into three classes, viz. symphysis, synarthrosis, and diarthrosis.

Symphysis, which properly signifies the concretion or growing together of parts, when used to express the articulations of bones, does not seem to comprehend, under the meaning generally given to it, any thing relating to the form or motion of the conjoined bones; but by it most authors only denote the bones to be connected by some other substance; and as there are different substances which serve this purpose, therefore they divide it into the three following species:

1. Synchondrosis, when a cartilage is the connecting substance: Thus the ribs are joined to the sternum; thus the bodies of the vertebrae are connected to each other; as are likewise the ossa pubis.

2. Synneurosis, or synedmosis, when ligaments are the connecting bodies, as they are in all the moveable articulations.

3. Synfascitis, when muscles are stretched from one bone to another, as they must be where there are moveable joints.

The second class of articulations, the synarthrosis, which is said to be the general term by which the immovable conjunction of bones is expressed, is divided into three kinds.

1. The suture is that articulation where two bones are mutually indented into each other, or as if they were sewed together. Thus the bones of the head are joined; thus epiphyses are joined to the bones, before their full connection and union with them.

2. Gomphosis is the fixing one bone into another, as a nail is fixed in a board: Thus the teeth are secured in their sockets.

3. Schindylesis, or ploughing, when a thin lamella of one bone is received into a long narrow furrow of another: Thus the processus zygous of the sphenoid, and the nasal process of the ethmoid bone, are received by the vomer.

The third class, or diarthrosis, is the articulation where the bones are so loosely connected as to allow large motion. This is subdivided into three kinds.

The

The first is enarthrosis, or the ball and socket, when a large head is received into a deep cavity; as the head of the os femoris is into the acetabulum coxendicis.

The second is arthrodia, when a round head is received into a superficial cavity; as in the articulation of the arm-bone and scapula. These two species of diarthrosis allow motion to all sides.

The third is ginglimus, which properly signifies the hinge of a door or window; in it the parts of the bones mutually receive and are received, and allow of motion two ways: Workmen call it charnal.

The ginglimus is generally divided into three kinds, to which some give the names of contiguous, dislant, and compound.

The first kind of ginglimus is, when a bone has several protuberances and cavities, which answer to as many cavities and processes of the other bone, with which it is articulated; as in the conjunction of the femur with the tibia.

The second species is, when a bone receives another at one end, and is received by the same bone at the other end; as in the radius and ulna.

The last sort is, when a bone receives another, and is received by a third; as in the oblique processes of the vertebrae.

If the moveable bones are not connected and kept firm by some strong substance, they would be luxated at every motion of the joints: and if their hard, rough, unequal surfaces were to play on each other, their motion would not only be difficult, but the loss of substance from attrition would be great. Therefore ligaments are made to obviate the first, and cartilages to prevent the other inconvenience. But because ligaments and cartilages turn rigid, inflexible, and rough, unless they are kept moist, a sufficient quantity of proper liquor is supplied for their lubrication, and to preserve them in a flexible state. Seeing then these parts are so necessary to the articulations, we shall next consider their structure, situation, and uses, so far as they are subservient to the bones, and their motions.

LIGAMENTS are whiteflexible bodies, thicker and firmer than membranes, and not so hard or firm as cartilages, without any remarkable cavity in their substance, difficultly stretched, and with little elasticity; serving to connect one part to another, or to prevent the parts to which they are fixed from being removed out of that situation which is useful and safe.

After maceration in water, the ligaments can easily be divided; and each ligamentous layer appears composed of fibres, the largest of which are disposed in a longitudinal direction.

The arteries of ligaments are very conspicuous after a tolerable injection, and the larger trunks of their veins are sometimes to be seen full of blood.

Such ligaments as form the sides of cavities, have numerous orifices of their arteries opening upon their internal surface, which keep it always moist: If we rub off that moisture, and then press the ligament, we can see the liquor ouzing out from small pores; and we can

force thin liquors, injected by the arteries, into the cavities formed by ligaments.

These exhalant arteries must have corresponding absorbent veins, otherwise the cavities would soon be too full of liquor.

Ligaments then must be subject to the diseases common to other parts, where there is a circulation of fluids, allowance always being made for the size of vessels, nature of the fluids, and firmness of the texture of each part.

Some authors have alledged, that ligaments are insensible, and consequently that they have no nerves. But the violent racking pain felt on the least motion of a joint labouring under a rheumatism, the seat of which disease seems often to be in the ligaments, and the insufferable torture occasioned by incisions of ligaments, and by a collection of acrid matter in a joint, or by topfi in the gout, would persuade us, that they are abundantly supplied with nerves.

The ligaments which connect the moveable bones commonly rise from the conjunction of the epiphyses of the one bone, and are inserted into the same place of the other; or where epiphyses are not, they come out from the cervix, and beyond the supercilia of the articulated bones; and after such a manner, in both cases, as to include the articulation in a purse or bag; with this difference, depending on their different motions, that where the motion is only to be in two directions, the ligaments are strongest on those sides towards which the bones are not moved; and when a great variety of motions is designed to be allowed, the ligaments are weaker than in the former sort of articulations, and are nearly of the same strength all round.

Part of the capsular ligaments is composed of the periosteum, continued from one bone to another, and their internal layer is continued on the parts of the bone or cartilage which the ligament includes.

Besides these common capsular ligaments of the joints, there are particular ones in several places, either for the firmer connection of the articulated bones, or for restraining and confining the motion to some one side; such are the cross and lateral ligaments of the knee, the round one of the thigh, &c.

From this account of the ligaments, we may conclude, that, ceteris paribus, in whatever articulation the ligaments are few, long, and weak, the motion is more free and quick; but luxations happen frequently: And, on the contrary, where the ligaments are numerous, short, and strong, the motion is more confined; but such a joint is less exposed to luxations.—Whence we may judge how necessary it is to attend to the different ligaments, and the changes which have been made on them by a luxation, when it is to be reduced.

Ligaments also supply the place of bones in several cases to advantage: Thus the parts in the pelvis are more safely supported below by ligaments, than they could have been by bone.—The ligaments placed in the great holes of the ossa innominata, and between the bones of the fore-arm and leg, afford convenient origin to muscles.—Immoveable bones are firmly connected by them;

of which the conjunction of the os sacrum and innominatum is an example.—They afford a socket for moveable bones to play in, as we see part of the astragalus does on the ligament stretched from the heel-bone to the scaphoid.

Numerous inconveniences may arise from too long or short, strong or weak, lax or rigid ligaments.

CARTILAGES are solid, smooth, white elastic substances, between the hardness of bones and ligaments, and covered with a membrane, named perichondrium, which is of the same structure and use to them as the periosteum is to the bones.

Cartilages are composed of plates, which are formed of fibres, disposed much in the same way as those of bones are; as might be reasonably concluded from observing bones in a cartilaginous state before they ossify, and from seeing, on the other hand, so many cartilages become bony. This may be still further confirmed, by the exfoliation which cartilages are subject to, as well as bones.

The perichondrium of several cartilages, for example, those of the ribs and larynx, has arteries which can be equally well injected with those of the periosteum.

The granulated flesh which rises from the ends of metacarpal or metatarsal bones, when the cartilage exfoliates, after a finger or toe has been taken off at the first joint, is very sensible, from which the existence of nerves in cartilages may be inferred.

While cartilages are in a natural state, it is to be remarked, first, That they have no cavity in their middle for marrow. Secondly, That their outer surface is softest, which renders them more flexible. Thirdly, That they do not appear to change their texture near so much by acids as bones do. And, lastly, That as the specific gravity of cartilages is near a third less than that of bones, so the cohesion of their several plates is not so strong as in bones; whence cartilages laid bare in wounds or ulcers, are not only more liable to corrupt, but exfoliate much sooner than bones do.

Cartilages seem to be principally kept from ossifying, either by being subjected to alternate motions of flexion and extension, the effects of which are very different from any kind of simple pressure, or by being constantly moistened: Thus, the cartilages on the articulated ends of the great bones of the limbs, and the moveable ones placed between the moving bones in some articulations, which are obliged to suffer many and different flexions, and are plentifully moistened, scarce ever change into bone; while those of the ribs and larynx are often ossified.

The cartilages subservient to bones, are sometimes found on the ends of bones which are joined to no other; but are never wanting on the ends, and in the cavities of such bones as are designed for motion.

The uses of cartilages, so far as they regard bones, are, to allow, by their smoothness, such bones as are designed for motion, to slide easily without detritus, while, by their flexibility, they accommodate themselves to the several figures necessary in different motions, and, by their elasticity, they recover their natural position and shape as soon as the pressure is removed.

This springy force may also assist the motion of the joint to be more expeditious, and may render shocks in running, jumping, &c. less.—To these cartilages we chiefly owe the security of the moveable articulations: For without them the bony fibres would sprout out, and intimately coalesce with the adjoining bone; whence a true ankylosis must necessarily follow; which never fails to happen when the cartilages are eroded by acrid matter, or ossified from want of motion or defect of liquor, as we see often happens after wounds of the joints, piodarthrocece, scrophula, and spina ventosa, or from old age, and long immobility of joints. The moveable cartilages interposed in joints, serve to make the motions both freer and more safe than they would otherwise be.—Those placed on the ends of bones that are not articulated, as on the spine of the os illium, base of the scapula, &c. serve to prevent the bony fibres from growing out too far.—Cartilages sometimes serve as ligaments, either to fasten together bones that are immovably joined, such are the cartilages between the os sacrum and ossa illium, the ossa pubis, &c. or to connect bones that enjoy manifest motion, as those do which are placed between the bodies of the true vertebrae, &c.—Cartilages very often do the office of bones to greater advantage, than these last could, as in the cartilages of the ribs, those which supply brims to cavities, &c.

Too great thickness or thinness, length or shortness, hardness or suppleness of cartilages, may therefore cause great disorders in the body.

The liquor, which principally serves to moisten the ligaments and cartilages of the articulations, is supplied by glands, which are commonly situated in the joint, after such a manner as to be gently pressed, but not destroyed by its motion. By this means, when there is the greatest necessity for this liquor, that is, when the most frequent motions are performed, the greatest quantity of it must be separated. These glands are soft and pappy, but not friable: In some of the large joints they are of the conglomerate kind, or a great number of small glandules are wrapt up in one common membrane. Their excretory ducts are long, and hang loose, like so many fringes, within the articulation; which, by its motion and pressure, prevents obstructions in the body of the gland or its excretories, and promotes the return of this liquor, when fit to be taken up by the absorbent vessels, which must be in the joints, as well as in the other cavities of the body; and, at the same time, the pressure on the excretory ducts hinders a superfluous unnecessary secretion, while the fimbriated disposition of these excretories does not allow any of the secreted liquor to be pushed back again by these canals towards the glands.

Very often these fountains of slimy liquor appear only as a net-work of vessels.—Frequently they are almost concealed by cellular membranes containing the fat;—and sometimes small simple mucous folliculi may be seen.

The different joints have these organs in different numbers and sizes; the conglomerate ones don't vary much, especially as to situation, in the similar joints of different bodies; but the others are more uncertain.

Upon pressing any of these glands with the finger, one can

can squeeze out of their excretories a mucilaginous liquor, which somewhat resembles the white of an egg, or serum of the blood; but it is manifestly salt to the taste. It does not coagulate by acids or by heat, as the serum does, but by the latter turns first thinner, and, when evaporated, leaves only a thin salt film.

The vessels which supply liquors for making the secretion of this mucilage, and the veins which bring back the blood remaining after the secretion, are to be seen without any preparation; and, after a tolerable injection of the arteries, the glands are covered with them.

In a found state, we are not conscious of any sensibility in those glands; but, in some cases, when they inflame and suppurate, the most racking pain is felt in them: a melancholy, though a sure proof that they have nerves.

These mucilaginous glands are commonly lodged in a cellular substance; which is also to be observed in other parts of the bag formed by the ligaments of the articulation; and contains a fatty matter, that must necessarily be attenuated, and forced through the including membranes into the cavity of the joint, by the pressure which it suffers from the moving bones.

After the liquor of the articulations becomes too thin and unserviceable, by being constantly pounded and rubbed between the moving bones, it is reassumed into the mass of blood by the absorbent vessels.

SECT. II. Of the S K E L E T O N.

AMONG anatomists, Skeleton is universally understood to signify the bones of animals connected together, after the teguments, muscles, bowels, glands, nerves, and vessels are taken away.

A skeleton is said to be a natural one, when the bones are kept together by their own ligaments; and it is called artificial, when the bones are joined with wire, or any other substance which is not part of the creature to which they belonged.

The human skeleton is generally divided into the HEAD, the TRUNK, the SUPERIOR and the INFERIOR EXTREMITIES.

OF THE HEAD.

By the Head is meant all that spheroidal part which is placed above the first bone of the neck. It therefore comprehends the cranium and bones of the face.

The cranium, helmet, or brain-case, consists of several pieces, which form a vaulted cavity, for lodging and defending the brain and cerebellum, with their membranes, vessels, and nerves.

The cavity of the cranium is proportioned to its contents. Hence such a variety of its size is observed in different subjects; and hence it is neither so broad nor so deep at its fore-part, in which the anterior lobes of the brain are lodged, as it is behind, where the large posterior lobes of the brain, and the whole cerebellum, are contained.

The external surface of the upper part of the cranium is very smooth, and equal, being only covered with the periosteum, (common to all the bones; but in the skull, distinguished by the name of pericranium), the thin frontal and occipital muscles, their tendinous aponeurosis, and with the common teguments of the body; while the external surface of its lower part has numerous risings, depressions, and holes, which afford convenient origin and insertion to the muscles that are connected to it, and allow safe passage for the vessels and nerves that run through and near it.

The internal surface of the upper part of the skull is commonly smooth, except where the vessels of the dura mater have made furrows in it, while the bones were soft.—Surgeons should be cautious when they trepan here, lest, in sawing or raising the bone where such furrows are, they wound these vessels.—In the upper part of the internal surface of several skulls, there are likewise pits of different magnitudes and figures, which seem to be formed by some parts of the brain being more luxuriant and prominent than others. Where these pits are, the skull is so much thinner than any where else, that it is often rendered diaphanous, the two tables being closely compacted without a diploe; the want of which is supplied by vessels going from the dura mater into a great many small holes observable in the pits.—The knowledge of these pits should teach surgeons to saw cautiously and slowly through the external table of the skull, when they are performing the operation of the trepan; since, in a patient whose cranium has these pits, the dura mater and brain may be injured, before the instrument has pierced near the ordinary thickness of a table of the skull.—The internal base of the skull is extremely unequal for lodging the several parts and appendices of the brain and cerebellum, and allowing passage and defence to the vessels and nerves that go into, or come out from these parts.

The bones of the cranium are composed of two tables, and intermediate cancelli, commonly called their diploe. The external table is thickest; the inner, from its thinness and consequent brittleness, has got the name of vitrea.

The diploe has much the same texture and uses in the skull, as the cancelli have in other bones.

The diploe of several old subjects is so obliterated, that scarce any vestige of it can be seen; neither is it observable in some of the hard craggy bones at the base of the skull. Hence an useful caution to surgeons who trust to the bleeding, want of resistance, and change of sound, as certain marks, in the operation of the trepan, for knowing when their instrument has sawed through the first table, and reached the diploe.

The cranium consists of eight bones, six of which are said to be proper, and the other two are reckoned common to it and to the face.—The six proper are, the os frontis, two ossa parietalia, two ossa temporum, and the os occipitis.—The common are, the os ethmoides, and sphenoides.

The os frontis forms the whole fore-part of the vault; the two ossa parietalia form the upper and middle part of it; the ossa temporum compose the lower part of the sides;

fides; the os occipitis makes the whole hinder part, and some of the base; the os ethmoides is placed in the fore-part of the base; and the os sphenoides is in the middle of it.

These bones are joined to each other by five sutures; the names of which are, the coronal, lambdoid, sagittal, and two squamous.

The coronal suture is extended over the head, from within an inch or so of the external canthus of one eye, to the like distance from the other; which being near the place where the ancients wore their vittæ, coronæ, or garlands, this suture has hence got its name.—Though the indentations of this suture are conspicuous in its upper part, yet an inch or more of its end on each side has none of them; for it is squamous and smooth there.

The lambdoid suture begins some way below, and farther back than the vertex or crown of the head, whence its two legs are stretched obliquely downwards, and to each side, in the form of the Greek letter $\backslash lambda$, and are generally said to extend themselves to the base of the skull.

This suture is sometimes very irregular, being made up of a great many small sutures, which surround so many little bones that are generally larger and more conspicuous on the external surface of the skull than internally. These bones are generally called triquetra, or Wormiana.

The sagittal suture is placed longitudinally, in the middle of the upper part of the skull, and commonly terminates at the middle of the coronal, and of the lambdoid sutures; between which it is said to be placed, as an arrow is between the string and bow.—However, this suture is frequently continued through the middle of the os frontis, down to the root of the nose; which oftener happens in women than men.

The squamous agglutinations, or false sutures, are one on each side, a little above the ear, of a semicircular figure, formed by the overlapping (like one scale upon another) of the upper part of the temporal bones, on the lower part of the parietal, where, in both bones, there are a great many small ridges and furrows, which are indented into each other; though these inequalities do not appear till the bones are separated.

The bones of the skull are joined to those of the face by schyndeleisis and sutures.—The schyndeleisis is in the partition of the nose.—The sutures said to be common to the cranium and face are five, viz, the ethmoidal, sphenoidal, transverse, and two zygomatic.—Parts however of these sutures are at the junction of only the bones of the skull.

The ethmoidal and sphenoidal sutures surround the bones of these names; and in some places help to make up other sutures, particularly the squamous and transverse; and, in other parts, there is but one suture common to these two bones.

The transverse suture is extended quite cross the face, from the external canthus of one orbit, to the same place of the other.

The zygomatic sutures are one on each side, being short, and flaring from above obliquely, downwards and backwards, to join a process of the cheek-bone to one of

the temporal bones, which advances towards the face; so that the two processes thus united, form a sort of bridge or jugum, under which the temporal muscle passes; on which account the processes, and sutures joining them, have been called zygomatic.

The advantages of the sutures of the cranium are these: 1. That this capsula is more easily formed and extended into a spherical figure, than if it had been one continued bone. 2. That the bones which are at some distance from each other at birth might then yield, and allow to the head a change of shape, accommodated to the passage it is engaged in. Whence, in hard labour of child-bed, the bones of the cranium, instead of being only brought into contact, are sometimes made to mount one upon the other. 3. That the dura mater may be more firmly suspended by its processes, which insinuate themselves into this conjunction of the bones; for doing this equally, and where the greatest necessity of adhesion is, the sutures are disposed at nearly equal distances, and the large reservoirs of blood, the sinuses, are under or near them. 4. That fractures might be prevented from reaching so far as they would in a continued bony substance. 5. That the connection at the sutures being capable of yielding, the bones might be allowed to separate; which has given great relief to patients from the violent symptoms which they had before this separation happened.

Having gone through the general structure of the cranium, we now proceed to examine each bone of which that brain-case consists.

The Os FRONTIS has its name from its being the only bone of that part of the face we call the forehead, though it reaches a good deal further. It has some resemblance in shape to the shell of the concha-bivalvis, commonly called the cockle; for the greatest part of it is convex externally, and concave internally, with a serrated circular edge; while the smaller part has processes and depressions, which make it of an irregular figure.

The external surface of the os frontis is smooth at its upper convex part; but several processes and cavities are observable below: for, at each angle of each orbit, the bone juts out to form four processes, two internal, and as many external; which, from this situation, may well enough be named angular. Between the internal and external angular processes of each side, an arched ridge is extended, on which the eye-brows are placed.—Very little above the internal end of each of these superciliary ridges, a protuberance may be remarked, in most skulls, where there are large cavities, called sinuses, within the bone.—Betwixt the internal angular processes, a small process rises, which forms some share of the nose, and thence is named nasal.—Some observe a protuberant part on the edge of the bone, behind each external angular process, which they call temporal processes; but these are inconsiderable.—From the under part of the superciliary ridges, the frontal bone runs a great way backwards; which parts may justly enough be called orbital processes. These, contrary to the rest of this bone, are concave externally, for receiving the globes of the eyes, with their muscles, fat, &c.

In each of the orbital processes, behind the middle of the superciliary ridges, a considerable sinosity is observed, where

where the glandula innominata Galeni, or lachrymalis, is lodged.—Behind each internal angular process, a small pit may be remarked, where the cartilaginous pally of the musculus obliquus major of the eye is fixed.—Betwixt the two orbital processes, there is a large discontinuation of the bone, into which the cribriform part of the os ethmoides is incased.—The frontal bone frequently has little caverns formed in it here where it is joined to the ethmoid bone.—Behind each external angular process, the surface of the frontal bone is considerably depressed where part of the temporal muscle is placed.

The foramina, or holes, observable on the external surface of the frontal bone, are three in each side.—One in each superciliary ridge, a little removed from its middle towards the nose; through which a twig of the ophthalmic branch of the fifth pair of nerves passes out of the orbit, with a small artery, from the internal carotid, to be distributed to the teguments and muscles of the forehead.—These vessels in some skulls make furrows in the os frontis, especially in the bones of children; and therefore we ought to beware of transverse incisions on either side of the os frontis, which might either open these vessels or hurt the nerves, while they are yet in part within the bone; for, when vessels are thus wounded, it is difficult to stop the hæmorrhagy, because the adhesion of a part of the artery to the bone hinders its contraction, and consequently slyptics can have little effect; the sides of the furrow keep off compressing substances from the artery; and we would wish to shun cauteries or escharotics, because they make the bone carious; and nerves, when thus hurt, sometimes produce violent symptoms.—But we must remark, that often, instead of a hole, a notch only is to be seen: Nay, in some skulls, scarce a vestige even of this is left; in others, both hole and notch are observable, when the nerve and artery run separately. Frequently a hole is found on one side, and a notch on the other; at other times we see two holes; or there is a common hole without, and two distinct entries internally. Near the middle of the inside of each orbit, hard by, or in the transverse suture, there is a small hole for the passage of the nasal twig of the first branch of the fifth pair of nerves, and of a branch of the ophthalmic artery. This hole is sometimes entirely formed in the os frontis; in other skulls, the sides of it are composed of this last bone, and of the os planum. It is commonly known by the name of orbitarium internum, though anterius should be added, because of the next, which is commonly omitted.—This, which may be called orbitarium internum posterius, is such another as the former; only smaller, and about an inch deeper in the orbit: through it a small branch of the ocular artery passes to the nose.—Besides these six, there are a great number of small holes observable on the outer surface of this bone, particularly in the two protuberances above the eye-brows. Most of these penetrate no further than the sinuses, or than the diploe, if the sinuses are wanting. The place, size, and number of them, are however uncertain: They generally serve for the transmission of small arteries or nerves.

The internal surface of the os frontis is concave, except at the orbital processes, which are convex, to sup-

port the anterior lobes of the brain. This surface is not so smooth as the external; for the larger branches of the arteries of the dura mater make some furrows in its sides and back-parts. The sinuities from the luxuriant risings of the brain, mentioned when describing the general structure of the cranium, are often very observable on its upper part; and its lower and fore parts are marked with the contorsions of the anterior lobes of the brain.—Through the middle of this internal surface, where always in children, and sometimes in old people, the bone is divided, either a ridge stands out, to which the upper edge of the falx is fastened, or a furrow runs, in which the upper side of the superior longitudinal sinus is lodged; on both these accounts chirurgical authors justly discharge the application of the trepan here.

Immediately at the root of this ridge or furrow there is a small hole, which sometimes pierces through the first table, and, in other skulls, opens into the superior sinus of the ethmoid bone within the nose. In it a little process of the falx is lodged, and a small artery, and sometimes a vein, runs; and the superior longitudinal sinus begins here.—This hole, however, is often not entirely proper to the os frontis; for in several skulls, the lower part of it is formed in the upper part of the base of the crista galli, which is a process of the ethmoid bone.

The os frontis is composed of two tables, and an intermediate diploe, as the other bones of the cranium are, and in a middle degree of thickness between the os occipitis and the parietal bones.

The diploe is also exhausted in that part above the eye-brows, where the two tables of the bone separate, by the external being protruded outwards, to form two large cavities, called sinus frontales.—These are divided by a middle perpendicular bony partition.—In some skulls, besides the large perpendicular septum, there are several bony pillars, or short partitions, found in each sinus; in others these are wanting.—For the most part, the septum is entire; at other times it is discontinued, and the two sinuses communicate.—Each sinus commonly opens by a roundish small hole, at the inner and lower part of the internal angular processes, into a sinus formed in the nose, at the upper and back part of the os unguis; near to which there are also some other small sinuses of this bone, the greater part of which open separately nearer the septum narium, and often they terminate in the same common canal with the large ones.

In a natural and sound state, these cavities are of considerable advantage; for the organ of smelling being thus enlarged, the effluvia of odorous bodies more difficultly escape it; and their impressions being more numerous, are therefore stronger, and affect the organ more.—These and the other cavities which open into the nose, increase the sound of our voice, and render it more melodious, by serving as so many vaults to resound the notes. Hence people labouring under a coryza, or stoppage of the nose from any other cause, when they are by the vulgar, though falsely, said to speak through their nose, have such a disagreeable harsh voice.—The liquor separated in the membrane of these sinuses, drills down upon the membrane of the nose to keep it moist.

From the description of these sinuses, it is evident,

how useless, nay, how pernicious it must be, to apply a trepan on this part of the skull; for this instrument, instead of piercing into the cavity of the cranium, would reach no further than the sinuses.

The upper circular part of the os frontis is joined to the ossa parietalia, from one temple to the other, by the coronal suture. From the termination of the coronal suture to the external angular processes, this bone is connected to the sphenoid by the sphenoidal suture. At the external canthi of the eyes, its angular processes are joined by the transverse suture to the ossa malarum, to which it adheres one third down the outside of the orbits; whence to the bottom of these cavities, and a little up on their internal sides, these orbital processes are connected to the sphenoidal bone by that same suture.—On the inside of each orbit, the orbital process is indented between the cribiform part of the ethmoid bone, and the os planum and unguis.—The transverse suture afterwards joins the frontal bone to the superior nasal processes of the ossa maxillaria superiora, and to the nasal bones. And, lastly, its nasal process is connected to the nasal lamella of the ethmoid bone.

The frontal bone serves to defend and support the anterior lobes of the brain. It forms a considerable part of the cavities that contain the globes of the eyes, helps to make up the septum narium, organ of smelling, &c. From the description of the several parts, the other uses of this bone are evident.

In a ripe child, the frontal bone is divided through the middle; the superciliary holes are not formed; often a small round piece of each orbital process, behind the superciliary ridge, is not ossified, and there is no sinus to be seen within its substance.

Each of the two OSSA PARIETALIA, or bones serving as walls to the encephalon, is an irregular square; its upper and fore sides being longer than the one behind or below. The inferior side is a concave arch; the middle part receiving the upper round part of the temporal bone.—The angle formed by this upper side and the fore one, is so extended, as to have the appearance of a process.

The external surface of each os parietale is convex. Upon it, somewhat below the middle height of the bone, there is a transverse arched ridge, of a whiter colour generally than any other part of the bone; from which, in bones that have strong prints of muscles, we see a great many converging furrows, like so many radii drawn from a circumference towards a centre. From this ridge of each bone the temporal muscle rises; and, by the pressure of its fibres, occasions the furrows just now mentioned.—Below these, we observe, near the semicircular edges, a great many risings and depressions, which are joined to like inequalities on the inside of the temporal bone, to form the squamous suture. The temporal bone may therefore serve here as a buttress, to prevent the lower side of the parietal from starting outwards when its upper part is pressed or struck.

Near the upper sides of these bones, towards the hind part, is a small hole in each, through which a vein passes from the teguments of the head to the longitudinal sinus.—In several skulls, one of the ossa parietalia has not this

hole; in others, there are two in one bone; and in some not one in either. Most frequently this hole is through both tables; at other times the external table is only perforated.—The knowledge of the course of these vessels may be of use to surgeons, when they make any incision near this part of the head, lest, if the vessels are rashly cut near the hole, they shrink within the substance of the bone, and so cause an obstinate hæmorrhagy, which neither ligatures nor medicines can stop.

On the inner concave surface of the parietal bones, we see a great many deep furrows, disposed somewhat like the branches of trees: The furrows are largest and deepest at the lower edge of each os parietale, especially near its anterior angle, where sometimes a full canal is formed. They afterwards divide into small furrows, in their progress upwards.—In some skulls a large furrow begins at the hole near the upper edge, and divides into branches, which join with those which come upwards, shewing the communications of the upper and lower vessels of the dura mater.—In these furrows we frequently see passages into the diploe. On the inside of the upper edge of the ossa parietalia, there is a large sinuosity, frequently larger in the bone of one side than of the other, where the upper part of the falx is fastened, and the superior longitudinal sinus is lodged.—Generally part of the lateral sinuses makes a depression near the angle, formed by the lower and posterior sides of these bones; and the pits made by the prominent parts of the brain are to be seen in no part of the skull more frequent, or more considerable, than in the internal surface of the parietal bones.

The ossa parietalia are amongst the thinnest bones of the cranium; but enjoy the general structure of two tables and diploe the completest, and are the most equal and smooth.

These bones are joined at their fore-side to the os frontis by the coronal suture; at their long inferior angles, to the sphenoid bone, by part of the suture of this name; at their lower edge, to the ossa temporum, by the squamous suture, and its posterior additamentum; behind, to the os occipitis, or ossa triquetra, by the lambdoid suture; and above, to one another, by the sagittal suture.

In a child born at the full time, none of the sides of this bone are completed; and there never is a hole in the ossified part of it near to the sagittal suture.

The large unossified ligamentous part of the cranium observable between the parietal bones, and the middle of the divided os frontis of new-born children, called by the vulgar the open of the head, was imagined by the ancients to serve for the evacuation of the superfluous moisture of the brain; and therefore they named it bregma, or the fountain; sometimes adding the epithet pulsatilis, or beating, on account of the pulsation of the brain felt through this flexible ligamento-cartilaginous substance. Hence very frequently the parietal bones are called ossa bregmatis.

All the bregma is generally ossified before seven years of age. Several authors say, they have observed it unossified in adults; and physicians, who order the application of medicines at the meeting of the coronal and sagittal

tal sutures, seem yet to think that a derivation of noxious humours from the encephalon is more easily procured at this part than any other of the skull; and that medicines have a greater effect here, than elsewhere, in the internal disorders of the head.

OSSA TEMPORUM, so named, say authors, from the hair's first becoming grey on the temples, and thus discovering peoples ages, are each of them equal and smooth above, with a very thin semicircular edge; which, from the manner of its connection with the neighbouring bones, is distinguished by the name of os squamosum.—Behind this, the upper part of the temporal bone is thicker, and more unequal, and is sometimes described as a distinct part, under the name of pars mammillaris.—Towards the base of the skull, the temporal bone appears very irregular and unequal; and this part, instead of being broad, and placed perpendicularly, as the others are, is contracted into an oblong very hard substance, extended horizontally forwards and inwards, which in its progress becomes smaller, and is commonly called os petrosum.

Three external processes of each temporal bone are generally described.—The first, placed at the lower and hind-part of the bone, from its resemblance to a nipple, is called mastoides, or mammillaris. It is not solid, but within is composed of cancelli, or small cells, which have a communication with the large cavity of the ear, the drum; and therefore sounds, being multiplied in this vaulted labyrinth, are increased, before they are applied to the immediate organ of hearing. Into the mastoid process, the stenosomatoideus muscle is inserted; and to its back-part, where the surface is rough, the trachelomastoides, and part of the splenius are fixed.—About an inch farther forward, the second process begins to rise out from the bone; and having its origin continued obliquely downwards and forwards for some way, it becomes smaller, and is stretched forwards to join with the os male; they together forming the bony jugum, under which the temporal muscle passes. Hence this process has been named zygomatic. Its upper edge has the strong aponeurosis of the temporal muscle fixed into it; and its lower part gives rise to a share of the masseter.—The fore-part of the base of this process is an oblong tubercle, which in a recent subject is covered with a smooth polished cartilage, continued from that which lines the cavity immediately behind this tubercle.—From the under craggy part of the os temporum, the third process stands out obliquely forwards. The shape of it is generally said to resemble the ancient stylus scriptorius; and therefore it is called the styloid process. Several muscles have their origin from this process, and borrow one half of their name from it; as stylo-glossus, stylo-hyoideus, stylo-pharyngeus: to it a ligament of the os hyoideus is sometimes fixed; and another is extended from it to the inside of the angle of the lower jaw. This process is often, even in adults, not entirely ossified, but is ligamentous at its root, and sometimes is composed of two or three distinct pieces.—Round the root of it, especially at the fore-part, there is a remarkable rising of the os petrosum, which some have esteemed a process; and, from the appearance it makes with the styliform, have named it vaginalis.—Others again have, under

the name of auditory process, reckoned among the external processes that semicircular ridge, which, running between the root of the mastoid and zygomatic processes, forms the under part of the external meatus auditorius.

The sinuities or depressions on the external surface of each os temporum are these:—A long fossa at the inner and back part of the root of the mammary process, where the posterior head of the digastric muscle has its origin.—Immediately before the root of the zygomatic process, a considerable hollow is left, for lodging the crotaphite muscle.—Between the zygomatic, auditory, and vaginal processes, a large cavity is formed; through the middle of which, from top to bottom, a fissure is observable, into which part of the ligament that secures the articulation of the lower jaw with this bone is fixed. The fore-part of the cavity being lined with the same cartilage which covers the tubercle before it, receives the condyle of the jaw; and in the back-part a small share of the parotid gland, and a cellular fatty substance, are lodged.—At the inside of the root of the styloid apophyse, there is a thimble-like cavity, where the beginning of the internal jugular vein, or end of the lateral sinus, is lodged.—Round the external meatus auditorius, several sinuities are formed for receiving the cartilages and ligaments of the ear, and for their firm adhesion.

The holes that commonly appear on the outside of each of these bones, and are proper to each of them, are five.—The first, situated between the zygomatic and mastoid processes, is the orifice of a large funnel-like canal, which leads to the organ of hearing; therefore is called meatus auditorius externus.—The second gives passage to the portia dura of the seventh pair of nerves; and, from its situation between the mastoid and styloid processes, is called foramen stylo mastoideum.—Some way before, and to the inside of the styloid process, is the third hole; the canal from which runs first upwards, then forwards, and receives into it the internal carotid artery, and the beginning of the intercostal nerve; where this canal is about to make the turn forwards, one, or sometimes two very small holes go off towards the cavity of the ear called tympanum: through these Valsalva affirms the proper artery or arteries of that cavity are sent.—On the anterior edge of this bone, near the former, a fourth hole is observable, being the orifice of a canal which runs outwards and backwards, in a horizontal direction, till it terminates in the tympanum. This, in the recent subject, is continued forward and inward, from the parts which were mentioned just now as its orifice in the skeleton, to the side of the nostrils: being partly cartilaginous, and partly ligamentous. The whole canal is named, Iter a palato ad aurem, or Eustachian tube.—On the external side of the bony part of this canal, and a-top of the chin in the cavity that receives the condyle of the lower jaw, is the course of the little nerve said commonly to be reflected from the lingual branch of the fifth pair, till it enters the tympanum, to run across this cavity, and to have the name of chorda tympani.—The fifth hole is very uncertain, appearing sometimes behind the mastoid process; sometimes it is common to the temporal and occipital bones; and in several skulls there

is no such hole. The use of it, when found, is for the transmission of a vein from the external teguments to the lateral sinus: But, in some subjects, a branch of the occipital artery passes through this hole, to serve the back-part of the dura mater.

The internal surface of the ossa temporum is unequal; the upper circular edge of the squamous part having numerous small ridges and furrows for its conjunction with the parietal bones; and the rest of it is irregularly marked with the convolutions of the middle part of the brain, and with furrows made by the branches of the arteries of the dura mater.

From the under part of this internal surface, a larger transverse, hard, craggy protuberance runs horizontally inwards and forwards, with a sharp edge above, and two flat sides, one facing obliquely forwards and outwards, and the other as much backwards and inwards. To the ridge between these two sides, the large lateral process of the dura mater is fixed.

Sometimes a small bone, akin to the sesamoid, is found between the small end of this petrous process and the sphenoid bone.

Towards the back-part of the inside of the os temporum, a large deep fossa is conspicuous, where the lateral sinus lies; and frequently on the top of the petrous ridge, a furrow may be observed, where a small sinus is situated.

The internal proper foramina of each of these bones are, first, the internal meatus auditorius in the posterior plain side of the petrous process. This hole soon divides into two; one of which is the beginning of the aqueduct of Fallopius: the other ends in several very small canals, that allow a passage to the branches of the portio mollis of the seventh pair of nerves, into the vestibule and cochlea. Through it also an artery is sent, to be distributed to the organ of hearing.—The second hole, which is on the anterior plain side of the craggy process, gives passage to a reflected branch of the second branch of the fifth pair of nerves, which joins the portio dura of the auditory nerve, while it is in the aqueduct, small branches of blood-vessels accompanying the nerves, or passing through smaller holes near this one.—The passage of the cutaneous vein into the lateral sinus, or of a branch of the occipital artery, is seen about the middle of the large fossa for that sinus; and the orifice of the canal of the carotid artery is evident at the under part of the point of the petrous process.

The upper round part of the squamous bones is thin, but equal; while the low petrous part is thick and strong, but irregular and unequal, having the distinction of tables and diploe confounded, with several cavities, processes, and bones within its substance, which are parts of the organ of hearing. See the description of the bones, muscles, &c. of the ear, in part VI.

The temporal bones are joined above to the parietal bones by the squamous sutures, and their posterior additamenta: Before, to the sphenoid bone by the suture of that name; to the cheek-bones by the zygomatic sutures: Behind, to the occipital bone, by the lambdoid suture and its additamenta; and they are articulated with the

lower jaw in the manner which shall be described when this bone is examined.

Os Occipitis, so called from its situation, is convex on the outside, and concave internally. Its figure is an irregular square, or rather rhomboid; of which the angle above is generally a little rounded; the two lateral angles are more finished, but obtuse; and the lower one is stretched forward in form of a wedge, and thence is called by some the cuneiform process.

The external surface is convex, except at the cuneiform apophyse, where it is flattened. At the base of this triangular process, on each side of the great hole, but more advanced forwards than the middle of it, the large oblong protuberances, named the condyles, appear, to serve for the articulation of this bone with the first vertebra of the neck. The smooth surface of each of these condylar processes is longest from behind forwards, where, by their oblique situation, they come much nearer to each other than they are at their back-part. Their inner sides are lower than the external, by which they are prevented from sliding to either side out of the cavities of the first vertebra.—Round their root a small depression and spongy roughness is observable, where the ligaments for surrounding and securing their articulations adhere.—Though the motion of the head is performed on the condyles, yet the centre of gravity of that globe does not fall between them, but is a good way further forward; from which mechanism it is evident, that the muscles which pull the head back must be in a constant state of contraction: which is stronger than the natural contraction of the proper flexors, else the head would always fall forwards, as it does when a man is asleep, or labours under a palsy, as well as in infants, where the weight of the head far exceeds the proportional strength of these muscles.

All round the great foramen the edges are unequal, for the firmer adhesion of the strong circular ligament which goes thence to the first vertebra.—One end of each lateral or moderator ligament of the head, is fixed to a rough surface at the fore-part of each condyle, and the perpendicular one is connected to a rough part of the edge of the great hole between the two condyles.

On the inner surface of the os occipitis we see two ridges; one standing perpendicular, the other running horizontally across the first. The upper part of the perpendicular limb of the cross, to which the falx is fixed, is hollowed in the middle, or often on one side, for the reception of the superior longitudinal sinus, and the lower part of it has the small or third process of the dura mater fastened to it, and is sometimes hollowed by the occipital sinus. Each side of the horizontal limb is made hollow by the lateral sinuses enclosed in the transverse process of the dura mater; the fossa in the right side being generally a continuation of the one made by the longitudinal sinus in the perpendicular limb, and therefore is larger than the left one.—Round the middle of the cross there are four large depressions separated by its limbs; the two upper ones being formed by the back-part of the brain, and the two lower ones by the cerebellum.—Farther forward than the last mentioned depressions,

pressions, is the lower part of the fossa for the lateral sinus on each side.—The inner surface of the cuneiform apophyse is made concave for the reception of the medulla oblongata, and of the basilar artery.—A furrow is made on each side, near the edges of this process, by a sinus of the dura mater, which empties itself into the lateral sinus.

The holes of this bone are commonly five proper, and two common to it and to the temporal bones.—The first of the proper holes, called foramen magnum, from its size, is immediately behind the wedge-like process, and allows a passage to the medulla oblongata, nervi accessorii, to the vertebral arteries, and sometimes to the vertebral veins.—At each side of this great hole, near its fore-part, and immediately above the condyles, we always find a hole, sometimes two, which soon unite again into one that opens externally; through these the ninth pair of nerves go out of the skull.—The fourth and fifth holes pierce from behind the condyle of each side, into the fossa of the lateral sinuses; they serve for the passage of the cervical veins to these sinuses. Often one of these holes is wanting, sometimes both, when the veins pass through the great foramen.—Besides these five, we frequently meet with other holes near the edges of this bone, for the transmission of veins; but their number and diameter are very uncertain. The two common foramina are the large irregular holes, one in each side, between the sides of the cuneiform process, and the edges of the petrous bones. In a recent subject, a strong membrane runs cross from one side to the other of each of these holes.

The occipital bone is among the thickest of the cranium, though unequally so; for it is stronger above, where it has no other defence than the common teguments, than it is below, where, being pressed by the lobes of the brain and cerebellum on one side, and by the action of the muscles on the other, it is so very thin, as to be diaphanous in many skulls.

The occipital bone is joined above to the ossa parietalia and triquetra when present, by the lambdoid suture;—laterally to the temporal bones, by the additamenta of the lambdoid suture;—below to the sphenoid bone, by the end of its cuneiform process, in the same way that epiphyses and their bones are joined.—The os occipitis is joined by a double articulation to the first vertebra of the neck, each condyle being received into a superior oblique process of that vertebra.

OS ETHMOIDES, or the sieve-like bone, has got its name from the great number of small holes with which that part of it first taken notice of is pierced. When this bone is entire, the figure of it is not easily described; but, by a detail of its several parts, some idea may be afforded of the whole; and therefore we shall distinguish it into the cribriform lamella with its process, the nasal lamella, cellulae, and ossa spongiosa.

The thin horizontal lamella, is all (except its back-part) pierced obliquely by a great number of small holes, through which the filaments of the olfactory nerves pass.—From the middle of the internal side of this plate, a thick process rises upwards, and, being highest at the fore-part, gradually becomes lower, as it is extended

backwards. From some resemblance which this process was imagined to have to a cock's comb, it has been called crista galli. The falx is connected to its ridge, and to the unperforated part of the cribriform plate.—When the crista is broke, its base is sometimes found to be hollow, with its cavity opening into the nose.

From the middle of the outer surface of the cribriform lamella, a thin solid plate is extended downwards and forwards, having the same common base with the crista galli. Generally it is not exactly perpendicular, but is inclined to one side or other, and therefore divides the cavity of the nose unequally. Its inclination to one side, and flexure in the middle, is sometimes so great, that it fills up a large share of one of the nostrils, and has been mistaken for a polypus there.—It is thin at its rise, and rather still thinner in its middle; yet afterwards, towards its lower edge, it becomes thicker, that its conjunction with the bones and middle cartilage of the nose might be firmer.

At a little distance from each side of this external process, a cellular and spongy bony substance depends from the cribriform plate. The number and figure of the cells in this irregular process of each side, are very uncertain; only the cells open into each other, and into the cavity of the nose: The uppermost, which are below the aperture of the frontal sinuses, are formed like funnels.—The outer surface of those cells is smooth and plain, where this bone assists in composing the orbit; at which place, on each side, it has got the name of os planum; on the upper edge of which, a small notch or two may sometimes be observed, which go to the formation of the internal orbital holes.

Below the cells of each side, a thin plate is extended inwards, and then bending down, it becomes thick, and of a spongy texture.—This spongy part is triangular, with a straight upper edge placed horizontally, an anterior one slanting from above, downwards and forwards, and with a pendulous convex one below.—The upper and lower edges terminate in a sharp point behind.—The side of this pendulous spongy part next to the septum narium is convex, and its external side is concave.—These two processes of the ethmoid bone have got the name of ossa spongiosa, or turbinata superiora, from their substance, figure, and situation.

All the prominences, cavities and meanders of this ethmoid bone, are covered with a continuation of the membrane of the nostrils, in a recent subject.—Its horizontal cribriform plate is lodged between the orbital processes of the frontal bone, to which it is joined by the ethmoid suture, except at the back-part, where it is connected with the cuneiform bone, by a suture common to both these bones.—Where the ossa plana are contiguous to the frontal bone within the orbit, their conjunction is reckoned part of the transverse suture.—Farther forward than the ossa plana, the cells are covered by the ossa unguis, which are not only contiguous to these cells, but cannot be separated from them, without breaking the bony substance.—Below the ossa unguis and plana, these cells and ossa spongiosa are overlapped by the maxillary bones.—The cellular part of each palate-bone is contiguous to each os planum and cells backwards.—The lower

lower edge of the nasal perpendicular plate is received into the furrow of the vomer.—Its posterior edge is joined to the fore-part of the processus azygos of the sphenoid bone.—Its upper edge joins the nasal process of the frontal and nasal bones, and its anterior one is connected to the middle cartilage of the nose.

From all which the uses of this bone are evident, viz. to sustain the anterior lobes of the brain: to give passage to the olfactory nerves, and attachment to the falx; to enlarge the organ of smelling, by allowing the membrane of the nose a great extent; to straiten the passage of the air through the nose, by leaving only a narrow winding canal, on the sensible membranous sides of which the substances conveyed along with the air must strike, to form part of the orbit of the eyes and septum narium; while all its parts are so light as not to be in hazard of separating by their weight; and they are so thin, as to form a large surface, without occupying much space.

OS SPHENOIDES, or wedge-like bone, so called because of its situation in the middle of the bones of the cranium and face, is of an irregular figure, and bears some faint resemblance to a bat with its wings extended.

When we view the external surface of the os sphenoides, two or three remarkable processes from each side of it may be observed; which are all of them again subdivided.—The first pair is the two large lateral processes or wings; the upper part of each of which is called the temporal process, because they join with the temporal bones in forming the temples, and the seat for some share of the crotaphite muscles. That part of the wings which juts out towards the inside, somewhat lower than the temporal apophyses, and is smooth and hollowed, where it makes up part of the orbit, is thence named orbital processes. Behind the edge separating these two processes, there is often a small groove, made by a branch of the superior maxillary nerve, in its passage to the temporal muscle. The lowest and back-part of each wing, which runs out sharp to meet the ossa petrosa, has been styled the spinous process: from near the point of which a sharp pointed process is frequently produced downwards, which some call styliform, that affords origin to the ptery-staphylinus externus muscle. From this styliform process a very small groove is extended along the edge of the bone to the hollow at the root of the internal plate of the following processes, which forms part of the Eustachian tube.—The second pair of external processes of the cuneiform bone is the two which stand out almost perpendicular to the base of the skull. Each of them has two plates, and a middle fossa facing backwards, and are named pterygoid or aliform processes. The external plates are broadest, and the internal are longest. From each side of the external plates, the pterygoid muscles take their rise. At the root of each internal plate, a small hollow may be remarked, where the musculus ptery-staphylinus internus, or circumflexus palati, rises, and some share of the cartilaginous end of the Eustachian tube rests; and, at the lower end of the same plate, is a hook-like rising or process, round which the tendon of the last named muscle plays, as on a pulley.—To these another pair may be added, to wit, the little triangular thin process, which comes from each side

of the body of the sphenoid bone, where the pterygoid processes are rising from it, and are extended over the lower part of the aperture of the sinus, as far as to join the ethmoid bone, while their body hangs down into the nares.—Besides these pairs of processes, there is a sharp ridge which stands out from the middle of its base: Because it wants a fellow, it may be called processus azygos. The lower part of this process, where it is received into the vomer, is thick, and often not quite perpendicular, but inclining more to one side than the other. The fore-part of this process, where it joins the nasal plate of the os ethmoides, is thin and straight.

The depressions, sinuities, and fossæ, on the external surface of this sphenoid bone, may be reckoned up to a great number, viz. two on the temporal apophyses where the crotaphite muscles lodge.—Two on the orbital processes, to make way for the globes of the eyes.—Two between the temporal and spinous processes, for receiving the temporal bones.—Two between the plates of the pterygoid processes, where the musculi pterygoidei interni and ptery-staphylini interni are placed.—Two between the pterygoid and orbital processes, for forming the holes common to this and to the cheek and maxillary bones.—Two on the lower ends of the aliform processes, which the palate-bones enter into.—Two at the roots of the temporal and pterygoid processes, where the largest share of the external pterygoid muscles have their rise.—Two at the sides of the processus azygos, for forming part of the nose, &c.

What was described under the name of temporal and spinous processes on the outside of the skull, are likewise seen on its inside, where they are concave, for receiving part of the brain; and commonly three apophyses on the internal surface of the sphenoid bone are only mentioned.—Two rising broad from the fore-part of its body, become smaller, as they are extended obliquely backwards.—The third standing on a long transverse base, near the back-part of the body of this bone, rises nearly erect, and of an equal breadth, terminating often in a little knob on each side. The three are called clinoid, from some resemblance which they were thought to have to the supporters of a bed.—From the roots of the anterior clinoid processes, the bone is extended on each side outwards and forwards, till it ends in a sharp point, which may have the name of the transverse spinous processes.—Between, but a little farther back than the two anterior clinoid processes, we see a protuberance considerably smaller than the posterior clinoid process, but of its shape.—Another process from between the transverse processes, often forces itself forwards into the os ethmoides.

Within the skull, there are two sinuities in the internal part of each wing of the sphenoid bone, for receiving the middle part of the brain.—One between the transverse spinous processes, for lodging the part of the brain where the crura medullæ oblongatæ are.—Immediately before the third or middle clinoid process, a single pit generally may be remarked, from which a fossa goes out on each side to the holes through which the optic nerves pass. The pit is formed by the conjoined optic nerves; and in the fossæ these nerves are lodged, as they

they run divided within the skull.—Between that third protuberance and the posterior clinoid process, the larger pit for the glandula pituitaria may be remarked. This cavity, because of its resemblance to a Turkish saddle, is always described under the name of fella Turcica, or ephippium.—On the sides of the posterior clinoid process a fossa may be remarked, that stretches upwards, then is continued forwards along the sides of the fella Turcica, near to the anterior clinoid processes, where a pit on each side is made. These fossæ point out the course of the two internal carotid arteries, after they have entered the skull.

The holes on each side of the os sphenoides are six proper, and three common.—The first is the round one immediately below the anterior clinoid processes, for the passage of the optic nerve, and of the branch of the internal carotid artery that is sent to the eye.—The second is the foramen lacerum, or large slit between the transverse spinous and orbital processes: Through it the third, fourth, the first branch of the fifth, and the greater share of the sixth pair of nerves, and an artery from the internal carotid, go into the orbit. Sometimes a small branch of the external carotid enters near its end, to be distributed to the dura-mater, and a vein, some call it the venous duct, or Nuck's aquaduct, returns through it to the cavernous sinus.—The third hole, situated a little below the one just now described, is called rotundum, from its shape. It allows passage to the second branch of the fifth pair of nerves, or superior maxillary nerve, into the bottom of the orbit.—The fourth is the foramen ovale, about half an inch behind the round hole. Through it the third branch of the fifth pair, or inferior maxillary nerve, goes out; and sometimes a vein from the dura mater passes out here.—Very near the point of the spinous process is the fifth hole of this bone: It is small and round, for a passage to the largest artery of the dura mater, which often is accompanied with a vein.—The sixth proper hole cannot be well seen, till the cuneiform bone is separated from all the other bones of the cranium; for one end of it is hid by a small protuberance of the internal plate of the pterygoid process, and by the point of the processus petrosus of the temporal bone. Its canal is extended above the inner plate of the pterygoid process; and where it opens into the cavity of the nose, it is concealed by the thin laminous part of the palate-bone. Through it a considerable branch of the second branch of the fifth pair of nerves is reflected.—Often in the middle of the fella Turcica, a small hole or two pierce as far as the cellular substance of the bone; and sometimes at the sides of this fella, one or more small holes penetrate into the sphenoidal sinuses.

The first of the common holes is that unequal fissure at the side of the fella Turcica, between the extreme point of the os petrosum and the spinous process of the cuneiform bone.—The second common hole is the large discontinuation of the external side of the orbit, left between the orbital processes of the cuneiform bone, the os maxillare, naſe, and palati. In this large hole the fat for lubricating the globe of the eye and temporal muscle is lodged, and branches of the superior maxillary nerve, with small arteries from the carotid and veins, pass.

—The third hole is formed between the base of this bone and the root of the orbital process of the palate-bone of each side. Through this a branch of the external carotid artery, and of the second branch of the fifth pair of nerves, are allowed a passage to the nostrils, and a returning vein accompanies them.

Under the fella Turcica, and some way farther forward, but within the substance of the sphenoid bone, are two sinuses, separated by a bony plate. Each of them is lined with a membrane, and opens into the upper and back part of each nostril by a round hole, which is at their upper fore-part. This hole is not formed only by the os sphenoides, which has an aperture near as large as any transverse section of the sinus, but also by the palate-bones which are applied to the fore-part of these sinuses, and close them up, that hole only excepted, which was already mentioned. Frequently the two sinuses are of unequal dimensions, and sometimes there is only one large cavity, with an opening into one nostril.

As this bone is extremely ragged and unequal, so its substance is of very different thickness, being in some places diaphanous; in others it is of a middle thickness, and its middle back-part surpasses the greatest share of the cranium in thickness.

The os sphenoides is joined, by its wings, to the parietal bones above, to the os frontis and ossa malarum before, to the temporal bones behind;—by the fore-part of its body and spinous processes, to the frontal and ethmoid bones;—by its back-part, behind the two sinuses, to the occipital, where it looks like a bone with the epiphyses taken off;—to the palate-bones, by the ends of the pterygoid processes, and still more by the fore-part of the internal plates of the pterygoid processes, and of the sinuses;—to the maxillary bones, by the fore-part of the external pterygoid plates;—to the vomer and nasal plate of the os ethmoides, by the processus azygos. All these conjunctions, except the last, which is a schindylis, are said to be by the future proper to this bone; though it is at first sight evident, that several other sutures, as the transverse, ethmoidal, &c. are confounded with it.

We see now how this bone is joined to all the bones of the cranium, and to most of the upper jaw; and therefore obtained the name of the wedge-like bone.

The FACE is the irregular pile of bones, composing the fore and under part of the head, which is divided into the upper and lower maxillæ or jaws.

The superior maxilla is the common designation given to the upper immovable share of the face. The shape of the superior jaw cannot easily be expressed; nor is it necessary, provided the shape and situation of all the bones which compose it are described. It is bounded above by the transverse suture, behind by the fore-part of the sphenoid bone, and below by the mouth.

The upper jaw consists of six bones on each side, of a thirteenth bone which has no fellow, placed in the middle, and of sixteen teeth. The thirteen bones are, two ossa nasi, two ossa unguis, two ossa malarum, two ossa maxillaria, two ossa palati, two ossa spongiosa inferiora, and the vomer.

The ossa nasi are placed at the upper part of the nose;—the ossa unguis are at the internal canthi of the orbits;—ossa malarum form the prominence of the cheeks;—ossa maxillaria form the side of the nose, with the whole lower and fore part of the upper jaw, and the greatest share of the roof of the mouth;—ossa palati are situated at the back-part of the palate, nostrils, and orbit;—ossa spongiosa are seen in the lower part of the nares;—and the vomer helps to separate these two cavities.

The bones of the upper jaw are joined to the bones of the skull by the schindylesis and futures already described as common to the cranium and face, and they are connected to each other by gomphosis and fifteen futures.

The gomphosis only is where the teeth are fixed in their sockets, and the schindylesis is only where the edges of the vomer are joined to other bones.

The first is the anterior nasal, which is straight, and placed longitudinally in the middle fore-part of the nose.

The second and third are the lateral nasal, which are at each side of the nose, and almost parallel to the first future.

Each of the two lacrymal is almost semicircular, and is placed round the lacrymal groove.

The sixth and seventh are the internal orbitar: each of which is extended obliquely from the middle of the lower side of an orbit to the edge of its base.

The two external orbitars are continued, each from the end of the internal orbitar, to the under and fore-part of the cheek.

The tenth is the mystachial, which reaches only from the lower part of the septum narium to between the two middle dentes incisores.

The longitudinal palate future stretches from the middle of the foremost teeth through the middle of all the palate.

The transverse palate one runs across the palate, nearer the back than the fore-part of it.

Each of the two palato-maxillary is at the back-part of the side of each nostril.

The fifteenth is the spinous, which is in the middle of the lower part of the nostrils. This may perhaps be rather thought a double schindylesis.

These futures of the face have not such conspicuous indentations as those of the skull have.

OSSA NASI, so named from their situation at the root of the nose, are each of an irregular oblong square figure, being broadest at their lower end, narrowest a little higher than their middle; and becoming somewhat larger at the top, where they are ragged and thickest, and have a curvature forwards, that their connection with the frontal bone might be stronger.—These bones are convex externally, and thereby better resist any violence from without; and they are concave internally, for enlarging the cavity of the nose.

The lower edge of these bones is unequal, and is stretched outwards and backwards, to join the cartilages of the nostrils.—Their anterior side is thick, especially above, and unequal, that their conjunction to each other might be stronger; and a small rising may be remarked

on their inner edge, where they are sustained by the septum narium.—Their posterior side, at its upper half, has externally a depression, where it is overlapped some way by the maxillary bones, while its lower half covers these bones: By which contrivance, they do not yield easily to pressure applied to their fore-part or sides.

A small hole is frequently to be observed on their external surface, into which two, three, or four holes, which appear internally, terminate for the transmission of small veins; sometimes the holes go no further than the cancelli of the bones.

The nasal bones are firm and solid, with very few cells or cancelli in them.

They are joined above to the frontal bone, by the middle of the transverse future;—behind, to the maxillary bones, by the lateral nasal futures;—below, to the cartilages of the nose;—before to one another, by the anterior nasal future;—internally, to the septum narium.

These bones serve to cover and defend the root of the nose.

OSSA UNGUIS, or LACRYMALIA, are so named, because their figure and magnitude are something near to those of a nail of one's finger, and because the tears pass upon them into the nose.

Their external surface is composed of two smooth concavities and a middle ridge.—The depression behind forms a small share of the orbit for the eye-ball to move on, and the one before is a deep perpendicular canal, or fossa, larger above than below, containing part of the lacrymal sac and duct. This is the part that ought to be pierced in the great operation for the filula lacrymalis.—This fossa of the bone is cribriform, or has a great number of small holes through it, that the filaments from the membrane which lines it, insinuating themselves into these holes, might prevent a separation of the membrane, and secure the bone in its natural situation.—The ridge between these two cavities of the os unguis, is the proper boundary of the orbit at its internal canthus; and beyond which surgeons should not proceed backwards in performing operations here.—The internal or posterior surface of this bone consists of a furrow in the middle of two convexities.

The substance of the os unguis is as thin as paper, and very brittle; which is the reason that those bones are often wanting in skeletons, and need little force to pierce them in living subjects.

Each of these bones is joined, above, to the frontal bone, by part of the transverse future;—behind, to the os planum of the ethmoid bone, by the same future;—before, and below, to the maxillary bone, by the lacrymal future;—internally, the ossa unguis cover some of the sinus ethmoidales.

These unguiform bones compose the anterior internal parts of the orbits, lodge a share of the lacrymal sac and duct, and cover the ethmoid cells.—Their situation and tender substance make a rash operator in danger of destroying a considerable share of the organ of smelling, when he is performing the operation of the filula lacrymalis.

OSSA MALARUM are the prominent square bones which form the cheek on each side.—Before, their surface

face is convex and smooth; backward, it is unequal and concave, for lodging part of the crotaphyte muscles.

The four angles of each of these bones have been reckoned processes by some.—The one at the external canthus of the orbit, called the superior orbital process, is the longest and thickest.—The second terminates near the middle of the lower edge of the orbit in a sharp point, and is named the inferior orbital process.—The third, placed near the lower part of the cheek, and thence called maxillary, is the shortest, and nearest to a right angle.—The fourth, which is called zygomatic, because it is extended backwards to the zygoma of the temporal bone, ends in a point, and has one side straight, and the other sloping.—Between the two orbital angles there is a concave arch, which makes about a third of the external circumference of the orbit, from which a fifth process is extended backwards within the orbit, to form near one third of that cavity; and hence it may be called the internal orbital process.—From the lower edge of each of the ossa malarum, which is between the maxillary and zygomatic processes, the masseter muscle takes its origin; and from the exterior part of the zygomatic process, the musculus distensor oris rises; in both which places the surface of the bone is rough.

On the external surface of each cheek bone, one or more small holes are commonly found, for the transmission of small nerves or blood-vessels from, and sometimes into the orbit.—On the internal surface are the holes for the passage of the nutritious vessels of these bones.—A notch on the outside of the internal orbital process of each of these bones assists to form the great slit common to this bone and to the sphenoid, maxillary, and palate-bones.

The substance of these bones is, in proportion to their bulk, thick, hard, and solid, with some cancelli.

Each of the ossa malarum is joined, by its superior and internal orbital processes, to the os frontis, and to the orbital process of the sphenoid bone, by the transverse future.—By the edge between the internal and inferior orbital processes, to the maxillary bone, by the internal orbital future.—By the side between the maxillary and inferior orbital process, again to the maxillary bone, by the external orbital future.—By the zygomatic process, to the os temporum, by the zygomatic future.

OSSEA MAXILLARIA SUPERIORA, are the largest bones, and constitute the far greater part of the upper jaw.

The processes of each os maxillare may be reckoned seven.—The first is the long nasal one at its upper and fore-part, which is broad below, and turns smaller, as it rises upwards, to make the side of the nose.—At the root of this, a transverse ridge may be observed within the nostrils, which supports the fore-part of the upper edge of the os spongiosum inferius.—The second is produced backwards and outwards, from the root of the nasal process, to form the lower side of the orbit; and therefore may be called orbital.—The edge of this orbital process, and the ridge of the nasal one, which is continued from it, make a considerable portion of the exter-

nal circumference of the orbit.—From the proper orbital process, a very rough triangular surface is extended downwards and outwards, to be connected to the cheekbone; and therefore may be called the malar process, from the lowest protuberant part of which some share of the masseter muscle takes its rise.—Behind the orbital process, a large tuberosity or bulge of the bone appears, which is esteemed the fourth process.—On the internal part of this we often meet with a ridge, almost of the same height with that in the nasal process, which runs transversely, and is covered by a similar ridge of the palate-bone, on which the back-part of the upper edge of the os spongiosum inferius rests.—The convex back-part of this tuberosity is rough for the origin of part of the external pterygoid muscle, and more internally is scabrous, where the palate and sphenoid bones are joined to it.—That spongy protuberance at the lower circumference of this bone, where the sockets for the teeth are formed, is reckoned the fifth.—The sixth is the horizontal plate, which forms the greater part of the base of the nostrils, and roof of the mouth; its upper surface, which belongs to the nostrils, is very smooth, but the other below is arched and rough, for the stronger adhesion of the membrane of the mouth, which is stretched upon it, and in chewing, speaking, &c. might otherwise be liable to be separated.—The seventh rises like a spine from the inner edge of the last, and forms a small part of the partition of the nostrils.

The depressions in each maxillary bone are, 1. A sinuosity behind the orbital process, made by the temporal muscle. 2. A pit immediately before the same process, where the origin of the musculus elevator labiorum communis, and elevator labii superioris, with a branch of the fifth pair of nerves, are lodged securely. 3. The hollow arch of the palate. 4. The semicircular great notch, or entry to the lower part of the nostrils, betwixt the root of the nasal process and spine of the palate-plate. 5. Sockets for the teeth: The number of these sockets is uncertain. 6. The lacrimal fossa in the nasal process, which assists the os unguis to form a passage for the lacrimal duct. Immediately on the outside of this, there is a small depression, from which the inferior or lesser oblique muscle of the eye has its origin. 7. The canal on the upper part of the great tuberosity within the orbit, which is almost a complete hole; in this a branch of the superior maxillary nerve passes.—Besides these, the superior surface of the great bulge is concave, to receive the under part of the eye.—Immediately above the transverse ridge in the nasal process, a small hollow is formed by the os spongiosum.

The holes of this bone are two proper and two common, which are always to be found, besides several others, whose magnitude, number, &c. are uncertain.—The first of the proper is the external orbital, immediately below the orbit, by which the infra-orbital branch of the second branch of the fifth pair of nerves, and a small artery, come out, after having passed in the canal, at the bottom of the orbit, described Numb. 7. of the depressions.—The second is the foramen incisivum, just behind the fore-teeth, which, at its under part, is one irregular hole common to both the maxillary bones when they

they are joined; but, as it ascends, soon divides into two, three, or sometimes more holes; some of which open into each nostril. Through them small arteries and veins, and a twig of the second branch of the fifth pair of nerves pass, and make a communication between, or join the lining coats of the nose and mouth.

The first common hole is that which appears at the inner side of the back-part of the tuberosity and of the sockets of the teeth, and is formed by a fossa in this bone, and a corresponding one in the os palati: through it a nerve, which is a branch of the second branch of the fifth pair, runs to the palate.—The other common hole is the great slit in the outside of the orbit described already, as the second common hole of the sphenoid bone.

All the body of the maxillary bone is hollow, and leaves a large sinus akin to the frontal and sphenoid, which is commonly, but unjustly, called antrum Highmorianum.—At the bottom of this cavity, we may often observe some protuberances, in which the small points of the roots of the teeth are contained.—This cavern and the sockets of the teeth are often divided by the interposition only of a very thin bony plate, which is liable to be eroded by acrid matter collected in the antrum, or to be broke in drawing a tooth. The symptoms of a collection of a matter here naturally lead us to the practice of pulling out the teeth, and piercing through this plate into the antrum, to procure an evacuation of the collected matter.

The maxillary sinuses have the same uses as the frontal and sphenoidal; and the situation of the sinuses is such, that the liquor drilling from them, from the cells of the ethmoid and palate-bones, and from the lacrimal ducts, may always moisten all the parts of the membrane of the nares in the different situations which the head is in.

The substance of the ossa maxillaria is compact and firm, except at the inferior processes, in which the teeth are lodged, where it is very spongy.

The maxillary bones are joined above by the upper ends of their nasal processes to the os frontis, by the transverse suture;—at the sides of these processes, to the ossa unguis, by the lacrimal sutures;—to the nasal bones, by the lateral nasal sutures;—by their orbital processes, to the cheek-bones, by the external orbital sutures;—by the internal sides of the internal orbital processes, to the ossa plana, by part of the ethmoidal suture;—by the back-part of the tuberosities, to the palate bones, by the suturæ palato-maxillares;—by the posterior edges of their palatine lamellæ, to the ossa palati, by the transverse palate-suture;—by their nasal spines, to the vomer, by the spinous suture;—by their sockets, to the teeth by gomphosis;—by the internal edge of the palate-plate, to one another, by the longitudinal palate-suture; on the upper and fore-part of which a furrow is left for receiving the cartilage which forms the partition of the nostrils;—between the fore-part of the nostrils and mouth, to each other, by the mystachial suture;—sometimes they are connected to the ossa spongiosa inferiora, by a plain concretion or union of substance.

These bones form the greater part of the nose and of the roof of the mouth, and a considerable share of the orbit. They contain sixteen teeth, give rise to muscles, transmission to nerves, &c. as mentioned in the description of their several parts.

Ossa PALATI are commonly described as two small square bones, at the back-part of the palate or roof of the mouth, though they are of much greater extent, being continued up the back-part of the nostrils to the orbit. Each palate-bone may therefore be divided into four parts, the palate square bone, the pterygoid process, nasal lamella, and orbital process.

The square bone is unequally concave, for enlarging both the mouth and cavity of the nose. The upper part of its internal edge rises in a spine, after the same manner as the palate-plate of the maxillary bone does, to be joined with the vomer.—Its anterior edge is unequally ragged, for its firmer connection with the palate-processes of the os maxillare.—The internal edge is thicker than the rest, and of an equal surface, for its conjunction with its fellow of the other side.—Behind, this bone is somewhat in form of a crescent, and thick, for the firm connection of the velum pendulum palati; the internal point being produced backwards, to afford origin to the palato-staphylinus, or azygos-muscle.—This square bone is well distinguished from the pterygoid process by a perpendicular fossa, which, applied to such another in the maxillary bone, forms a passage for the palatine branch of the fifth pair of nerves; and by another small hole behind this, through which a twig of the same nerve passes.

The pterygoid process is somewhat triangular, having a broad base, and ending smaller above. The back-part of this process has three fossæ formed in it; the two lateral receive the ends of the two plates of the sphenoid bone, that are commonly compared to a bat's wing; the middle fossa makes up a part of what is commonly called the fossa pterygoidea; the fore-side of this palatine pterygoid process is an irregular concave, where it receives the back-part of the great tuberosity of the maxillary bone.—Frequently several small holes may be observed in this triangular process, particularly one near the middle of its base, which, a little above, communicates with the common and proper holes of this bone already taken notice of.

The nasal lamella of this bone is extremely thin and brittle, and rises upwards from the upper side of the external edge of the square bone, and from the narrow extremity of the pterygoid process; where it is so weak, and at the same time so firmly fixed to the maxillary bone, as to be very liable to be broken in separating the bones.—From the part where the plate rises, it runs up broad on the inside of the tuberosity of the maxillary bone, to form a considerable share of the sides of the maxillary sinus, and to close up the space between the sphenoid and the great bulge of the maxillary bone, where there would otherwise be a large slit opening into the nostrils. From the middle internal side of this thin plate, a cross ridge, placed on such another of the maxillary bone, is extended; on it the back-part of the os spongiosum

spongiosum inferius rests.—Along the outside of this plate, the perpendicular fossa made by the palate-nerve is observable.

At the upper part of this nasal plate, the palate-bone divides into two processes, which were already named orbital;—between which and the body of the sphenoid bone, that hole is formed, which was mentioned as the last of the holes common to the sphenoid bone.—Sometimes this hole is wholly formed in the os palati, by a cross plate going from the one orbital process to the other. A nerve, artery, and vein belonging to the nostrils, pass here.—The anterior of the two orbital processes is the largest, and has its fore-part contiguous to the back-part of the maxillary sinus, and its upper surface appears in the bottom of the orbit, behind the back-part of the os maxillare and planum.—It has cells behind, resembling those of the ethmoid bone, to which it is contiguous; it is placed on the aperture of the sinus sphenoidal, so as to leave only a round hole at its upper fore-part.—The other part of the orbital process is extended along the internal side of the upper back-part of the maxillary tuberosity, to the base of the sphenoid bone, between the root of the processus azygos and the pterygoid process.

The palate-bones are joined to the maxillary, by the fore-edge of the palate square-bone, by the transverse palate-future:—By their thin nasal plates, and part of their orbital processes, to the same bones, by the palato-maxillares futures:—By their pterygoid processes, and back-part of the nasal plates, to the alæ vespertilionum, by the sphenoid future:—By the transverse ridges of the nasal plates, to the ossa spongiosa inferiora, by contact; hence frequently there is an intimate union of the substance of these bones in old skulls:—By the orbital processes, to the ossa plana and cellulæ ethmoidæ, by the ethmoid future:—To the body of the sphenoid bone, by the sphenoid future:—By the internal edge of the square-bones, to each other, by the longitudinal palate-future; and by their nasal spines, to the vomer, by the spinous future.

The palate-bones form part of the palate, nostrils, orbits, and fossæ pterygoideæ, and they cover part of the sinus maxillares, sphenoidales, and ethmoides.

OSSA TURBINATA, or spongiosa inferiora, resemble the superior ossa spongiosa in shape and substance, but have their anterior and upper edges contiguous to the transverse ridges of the nasal processes of the maxillary and palate-bones.—From their upper straight edge, two small processes stand out: the posterior, which is the broadest, descends to cover some of the antrum Highmorianum; the anterior rises up to join the os unguis, and to make part of the lacrimal duct.

Below the spongy bones already mentioned, there are sometimes two others, one in each nostril, which seem to be a production of the sides of the maxillary sinus turned downwards. When this third sort of spongy bones is found, the middle one of the three in each nostril is the largest, and the lowest is the smallest.—Besides all these, there are often several other small bones standing out into the nostrils, that, from their shape,

might also deserve the name of turbinata, but are uncertain in their bulk, situation, and number.

They are joined to the ossa maxillaria, palati, and unguis, especially in old subjects.

Their use is, to straiten the nostrils, to afford a large surface for extending the organ of smelling, to cover part of the antra maxillaria, and to assist in forming the under part of the lacrimal ducts, the orifices of which into the nose are concealed by these bones.

VOMER, or bone resembling a ploughshare, is the thirteenth of the upper jaw, without a fellow, forming the lower and back-parts of the partition of the nose.

The figure of this bone is an irregular rhomboid.—Its sides are flat and smooth.—Its posterior edge appears in an oblique direction at the back-part of the nostrils.—The upper one is firmly united to the base of the sphenoid bone, and to the nasal plate of the ethmoid; and, when it can be got separated, is hollow, for receiving the processus azygos of the sphenoid.—The anterior edge has a long furrow in it, where the middle cartilage of the nose enters.—The lower edge is firmly united to the nasal spines of the maxillary and palate-bones.—These edges of this bone are much thicker than its middle, which is as thin as the finest paper.

Its situation is not always perpendicular, but often inclined and bended to one side, as well as the nasal plate of the ethmoid-bone.

The vomer is convex at its upper part, and then is straight as it is extended downwards and forwards, where it is composed of two plates; the edges of which have a great number of small processes, disposed somewhat like the teeth of a saw, but more irregularly, and several of them are reflected back. Between these plates, a deep fossa is left, which, so far as the top of the curvature, is wide, and has strong sides, for receiving the processus azygos of the sphenoid-bone. Beyond the arch forwards, the fossa is narrower and shallower gradually to the point of the bone, receiving for some way the nasal lamella ethmoidæa, which is so closely united to the vomer, by the little processes piercing into its substance, as to prevent any separation. The middle cartilage of the nose fills up what remains of the fossa at its fore-part.

The posterior edge of the vomer, which appears above the back-part of the palate-bones, is broader above; but as it descends forwards, becomes thinner, though it is still solid and firm.—The lower edge of this bone, which rests on the nasal spine of the palate and maxillary bones, has a little furrow on each side, of a small middle ridge, answering to the spines of the bones of different sides, and the interstice between them. This edge and the upper one meet in the pointed fore-end of this bone.

The body of the vomer has a smooth surface, and solid, but thin substance; and towards its sides, where it is thickest, some cancelli may be observed, when the bone is broken.

It is joined above to the sphenoid and ethmoid bones, and to the middle cartilage of the nose, by schindylesis;—below, to the maxillary and palate-bones, by the spinous future.

The

The vomer divides the nostrils, enlarges the organ of smelling, by allowing place for expanding the membrane of the nose on its sides, and sustains the palate-plates of the maxillary and palate-bones.

MAXILLA INFERIOR, the lower jaw, consists only of one moveable bone, and sixteen teeth incased into it.

This bone, which is somewhat of the figure of the Greek letter v, is situated at the lower part of the face, so as its convex middle part is forwards, and its legs are stretched back. It is commonly divided into the chin, sides, and processes.—The chin is the middle fore-part, the extent of which to each side is marked on the external surface by the holes observable there, and internally, by the beginning of an oblique ridge.—Beyond these, the sides appear, and are continued till the bone, by bending upwards, begins to form the processes.

On the fore-part of the chin, a transverse ridge appears in the middle, on each side of which the musculi quadrati, or depressores labii inferioris, and the levator labii inferioris, depress the bone: And below these prints, a small rising may be observed, where the depressores commence.—On the back-part of the chin, sometimes three, always two, small protuberances appear in the middle. To the uppermost, when it is seen, the frænum of the tongue is connected. From the middle one, the musculi genioglossi rise; and from the lowest, the geniohyoidei have their origin.

At the lower and fore-part of the external surface of each side of the lower jaw, a small eminence may be observed, where the depressor labiorum communis rises. Near the upper edge of the side a ridge runs length-ways, to which the under part of the musculus buccinator is connected.—Internally, towards the upper edge of each side, another ridge appears, from which the mylohyoidei have their origin, and to which the internal membrane of the gums adheres.

In the upper edge of both chin and sides are a great many deep pits or sockets, for receiving the roots of the teeth. The number and magnitude of these sockets are various, because of the different number, as well of the teeth themselves, as of their roots, in different people. These sockets in this lower jaw, as well as in the upper one, are less deep as old age comes on; when freed from the teeth by any means, they are some time after filled up with an osseous net-work, which at last becomes entirely solid, and as smooth as any other part of the bone; so that in a great many old jaws one cannot observe a vestige of the sockets: But then the jaw becomes less, and much narrower.—Hence we may know why the chin and nose of edentulous people are much nearer than before the teeth were lost; while their lips either fall in towards the mouth, or stand prominent forwards.—When new teeth are protruded, new sockets are formed.—The lower edge of the chin and sides is smooth and equal, and is commonly called the base of the lower jaw.—The ends of the base, where the jaw turns upwards, are called its angles; the external surface of each of which has several inequalities upon it, where the masseter muscle is inserted; as the internal surface also has, where the pterygoideus internus is inserted, and a liga-

ment, extended from the styloid process of the temporal bone, is fixed.

The processes are two on each side.—The anterior sharp thin coronoid ones have the crotaphyte muscles inserted into them.—The posterior processes, or condyles, terminate in an oblong smooth head, supported by a cervix. The heads, whose greatest length is transverse, and whose convexity is turned forwards, are tipped with a cartilage, as the articulated parts of all other moved bones are.—The fore-part of the root and neck of these condyloid processes are a little hollow and rough, where the external pterygoid muscles are inserted.

The holes of the lower jaw are two on each side; one at the root of the processes internally, where a large branch of the third branch of the fifth pair of nerves enters with an artery, and a vein returns. A small sharp process frequently juts out backwards from the edge at the fore-part of this hole, to which a ligament, extended from the temporal bone, is fixed, which saves the nerve and vessels from being too much pressed by the pterygoid muscles.—From the lower side of this hole, either a small superficial canal or a furrow descends, where a branch of the nerve is lodged, in its way to the mylohyoideus muscle and sublingual gland.—The other hole is external, at the confines of the chin, where branches of the nerve and vessels come out.—The canal betwixt these two holes is formed in the middle of the substance of the bone, and is pierced by a great number of small holes by which the nerves and blood-vessels of the cancelli and teeth pass.

The lower jaw generally receives the roots of sixteen teeth into its sockets, by gomphosis; and its condyloid processes, covered with cartilage, are articulated with the temporal bones.

The TEETH are the hard white bodies placed in the sockets of both jaws. Their number is generally sixteen above, and as many below; though some people have more, others have fewer.

The broad thick part of each tooth which appears without the socket, is the base, or body.—The smaller processes sunk into the maxillæ, are the roots or fangs, which become gradually smaller towards the end farthest from the base, or are nearly conical, by which the surface of their sides divides the pressure made on the bases, to prevent the soft parts, which are at the small points of the sockets, to be hurt by such pressure.

Without the gums the teeth are covered with no membrane, and they are said to have no proper periosteum within the sockets; but that is supplied by the reflected membrane of the gums; which, after a good injection, may be evidently seen in a young subject, with the vessels from it penetrating into the substance of the teeth; and it may be discovered in any tooth recently pulled, by macerating it in water. The adhesion of this membrane to these roots is strengthened by the small furrows observable on them.

Each tooth is composed of its cortex, or enamel, and an internal bony substance. The cortex has no cavity or place for marrow; and is so solid and hard, that saws or files can with difficulty make impression on it. It is thickest

thickest upon the base, and gradually, as the roots turn smaller, becomes thinner.—The fibres of this enamel are all perpendicular to the internal substance, and are straight on the base, but at the sides are arched with a convex part towards the roots; which makes the teeth resist the compression of any hard body between the jaws, with less danger of breaking these fibres, than if they had been situated transversely. The spongy sockets in which the teeth are placed likewise serve better to prevent such an injury, than a more solid base would have done.

The bony part of the teeth has its fibres running straight, according to the length of the teeth. When it is exposed to the air, by the breaking or falling off of the hard cortex, it soon corrupts. And thence carious teeth are often all hollow within, when a very small hole appears only externally.

The teeth have canals formed in their middle, wherein their nerves and blood-vessels are lodged; which they certainly need, being constantly wasted by the attrition they are subjected to in manducation, and for their further growth, not only after they first appear, but even in adults; as is evident when a tooth is taken out: For then the opposite one becomes longer, and those on each side of the empty socket turn broader; so that when the jaws are brought together, it is scarce observable where the tooth is wanting.

The vessels are easily traced so long as they are in the large canal, but can scarce be observed in their distribution from that to the substance of the teeth of adults.—This plentiful supply of vessels must expose the teeth to the same disorders that attack other vascular parts.

Every root of each tooth has such a distinct canal, with vessels and nerves in it. These canals in the teeth with more than one root, come nearer each other, as they approach the base of the tooth: and at last are only separated by very thin plates, which being generally incomplete, allow a communication of all the canals; and frequently one common cavity only appears within the base, in which a pulpy substance, composed of nerves and vessels, is lodged.

The entry of the canals for these vessels is a small hole placed a little to a side of the extreme point of each root; sometimes, especially in old people, this hole is entirely closed up, and consequently the nerves and blood-vessels are destroyed.

The teeth are seen for a considerable time in form of mucus contained in a membrane; afterwards a thin cortical plate, and some few osseous layers appear within the membrane, with a large cavity filled with mucus in the middle; and gradually this exterior shell turns thicker, the cavity decreases, the quantity of mucus is lessened, and this induration proceeds till all the body is formed; from which the roots are afterwards produced.

In young subjects, different stamina, or rudiments of teeth, are to be observed. Those next the gums hinder ordinarily the deeper-seated ones from making their way out, while these prevent the former from sending out roots, or from entering deep into the bony sockets of the jaws; by which they come to be less fixed.

Children are seldom born with teeth; but at two

years of age they have twenty; and their number does not increase till they are about seven years old, when the teeth that first made their way through the gums are thrust out by others that have been formed deeper in the jaw, and some more of the teeth begin to discover themselves farther back in the mouth. About fourteen years of age, some more of the first crop are shed, and the number is increased.—This shedding of the teeth is of good use; for if the first had remained, they would have stood at a great distance one from another; because the teeth are too hard in their outer crust, to increase so fast as the jaws do. Whereas both the second layer, and the teeth that come out late, meeting, while they are soft, with a considerable resistance to their growth in length, from those situated upon them, necessarily come out broad, and fit to make that close guard to the mouth, which they now form.

The teeth are joined to the sockets by gomphosis, and the gums contribute to fix them there; as is evident by the teeth falling out when the gums are any way destroyed, or made too spongy; as in the scurvy or salivations: Whence some class this articulation with the sphenoid.

The uses of the teeth are to masticate our aliment, and to assist us in the pronunciation of several letters.

Though the teeth so far agree in their structure, yet, because of some things wherein they differ, they are generally divided into three classes, viz. incisores, canini, and molares.

The incisores, are the four fore-teeth in each jaw, receiving their name from their office of cutting our aliment; for which they are excellently adapted, being each formed into a sharp-cutting edge at their base, by their fore-side turning inwards there, while they are slopped down and hollowed behind; so that they have the form of wedges; and therefore their power of acting must be considerably increased.

The incisores of the upper jaw, especially the two middle ones, are broader and longer generally than those of the under jaw.

Canini, from the resemblance to dogs' tusks, are one on each side of the incisores in each jaw.—The two in the upper jaw are called eye-teeth, from the communication of nerves which is said to be betwixt them and the eyes.—The two in the lower jaw are named angular, or wike-teeth, because they support the angles of the mouth.

The canini are broader, longer, and stronger, than the incisores.—Their bases are formed into a sharp edge, as the incisores are; only that the edge rises into a point in the middle.—Each of them has generally but one long root, though sometimes they have two. The roots are crooked towards the end.—The canini of the upper jaw are larger, longer, and with more crooked roots, than those of the under jaw.

The dentes molares, or grinders, which have got their name because they grind our food, are generally five in each side of each jaw; in all twenty. Their bases are broader, more scabrous, and with a thinner cortical substance, than the other teeth. They have also more

roots, and as these roots generally divaricate from each other, the partitions of the sockets between them bear a large share of the great pressure they suffer, and hinder it to act on their points.

The numerous roots of the dentes molares prevent their loosening by the lateral pressure they suffer in grinding; and as the sockets in the upper jaw are more spongy, and the teeth are more liable, by their situation, to fall out, the grinders there have more numerous and more separated roots than in the lower jaw.

According to the division made of the skeleton, we should now proceed to the description of the trunk of the body. But must first consider a bone, which cannot well be said to belong to either the head or the trunk; nor is it immediately joined to any other, and therefore is very seldom preserved with skeletons.

The OS HYOIDES, which is situated horizontally between the root of the tongue and the larynx. It is properly enough named hyoides, from the resemblance it bears to the Greek letter υ, and may, for a clearer demonstration of its structure, be distinguished into its body, cornua, and appendices.

The body is the middle broad part, convex before, and hollow behind.—The convex fore-part is divided into two, by a ridge, into the middle of which the mylo-hyoidei, and into the sides the stylo-hyoidei, muscles are inserted.—Above the ridge, the bone is horizontal, but pitted in the middle by the insertion of the two genio-hyoidei muscles, and a little hollowed more laterally by the basiglossi.—Below the ridge, it is convex, but a little flattened in the middle by the sterno-hyoidei, and pitted more externally by the coraco-hyoidei.—The concavity behind faces backwards and downwards to receive the thyroid cartilage, when the larynx and the os hyoides are pulled towards each other by the action of the sterno-hyoidei and hyothyroidei muscles; and to its upper edge, the ligamentous membranes of the epiglottis, tongue, and thyroid cartilage, are fixed.

The cornua of the os hyoides are stretched backwards from each side of its body, where often a small furrow points out the former separation.—These cornua are not always straight, nor of equal length; their two plain surfaces stand obliquely sloping from above, outwards and downwards.—Into the external, the ceratoglossus is inserted above, and the thyro-hyoideus muscle below; and to the one behind, the ligamentous membrane of the tongue and larynx adheres. Each of the cornua becomes gradually smaller, as it is extended from the base; but ends in a round tubercle, from which a moveable cartilage stands out, which is connected to the upper process of the cartilage thyroidea.

Where the body of the os hyoides joins on each side with its cornua, a small styliform process, called appendix, rises upwards and backwards, into which the muscles stylo-hyoidei alteri, and part of the hyo-glossi muscles are fixed.

The substance of the os hyoides is cellular, but covered with a firm external plate, which is of sufficient strength to bear the actions of so many muscles as are inserted into it.

It is not articulated with any bone of the body, except by means of the muscles and ligaments mentioned.

The use of the os hyoides, is to serve as a solid lever for the muscles to act with, in raising or depressing the tongue and larynx, or in enlarging and diminishing the capacity of the fauces.

OF THE TRUNK.

THE TRUNK consists of the spine, pelvis, and thorax.

THE SPINE is the long pile of bones extended from the condyles of the occiput to the end of the rump.—It somewhat resembles two unequal pyramids joined in a common base. It is not, however, straight; for its upper part being drawn backwards by strong muscles, it gradually advances forwards, to support the œsophagus, vessels of the head, &c. Then it turns backwards, to make place enough for the heart and lungs. It is next bent forwards, to support the viscera of the abdomen. It afterwards turns backwards, for the enlargement of the pelvis. And, lastly, it is reflected forwards, for sustaining the lowest great gut.

The spine is commonly divided into true and false vertebrae; the former constituting the long upper pyramid, which has its base below, while the false vertebrae make the shorter lower pyramid, whose base is above.

THE TRUE VERTEBRÆ are the twenty-four upper bones of the spine, on which the several motions of the trunk of our bodies are performed; from which use they have justly got their name.

Each of these vertebrae is composed of its body and processes.

The body is the thick spongy fore-part, which is convex before, concave backwards, horizontal and plain in most of them above and below.—Numerous small holes, especially on the fore and back-part of their surface, give passage to their vessels, and allow the ligaments to enter their substance.—The edges of the body of each vertebra are covered, especially at the fore-part, with a ring of bone firmer and more solid than the substance of the body any where else. These rings are of great use in preventing the spongy bodies from being broken in the motions of the trunk.

Between the bodies of each two adjoining vertebrae, a substance between the nature of ligament and cartilage is interposed; which seems to consist of concentrical curve fibres, when it is cut horizontally; but when it is divided perpendicularly, the fibres appear oblique and decussating each other.—The outer part of the intervertebral ligaments is the most solid and hard; and they gradually become softer till they are almost in the form of a glairy liquor in the centre; and therefore these substances were not improperly called mucous ligaments by the ancients. The external fibrous part of each is capable of being greatly extended, and of being compressed into a very small space, whilst the middle fluid part is incompressible, or nearly so; and the parts of this ligament between the circumference and centre approach in their properties to either, in proportion to their more solid

or more fluid texture. The middle point is therefore a fulcrum or pivot, on which the motion of a ball and focket may be made, with such a gradual yielding of the substance of the ligament, in whichever direction our spines are moved, as saves the body from violent shocks, and their dangerous consequences.—This ligamentocartilaginous substance is firmly fixed to the horizontal surfaces of the bodies of the vertebrae, to connect them, in which it is assisted by a strong membranous ligament, which lines all their concave surface, and by still a stronger ligament, that covers all their anterior convex surface.

From each side of the body of each vertebra, a bony bridge is produced backwards, and to a side: from the posterior end of which, one flanting process rises and another descends; the smooth, and what is generally the flattest side of each of these four processes, which are called the oblique, is covered with a smooth cartilage; and the two lower ones of each vertebra, are fitted to, and articulated with the two upper or ascending oblique processes of the vertebra below, having their articular ligaments fixed into the rough line round their edges.

From between the oblique processes of each side the vertebra is stretched out laterally into a process that is named transverse.

From the back-part of the roots of the two oblique, and of the transverse process of each side, a broad oblique bony plate is extended backwards, where these meet, the seventh process of the vertebrae takes its rise, and stands out backwards: This being generally sharp pointed, and narrow edged, has therefore been called spinal process; from which this whole chain of bones has got its name.

Besides the common ligament which lines all the internal surface of the spinal processes, as well as of the bodies, there are particular ligaments that connect the bony bridges and processes of the contiguous vertebrae together.

The substance of the processes is considerably stronger and firmer, and has a thicker external plate than the bodies of the vertebrae have.

The seven processes form a concavity at their fore-part, which, joined to the one at the back-part of the bodies, makes a great hole, and the holes of all the vertebrae form a long large conduit, for containing the spinal marrow.—In the upper and lower edge of each lateral bridge, there is a notch. These are so adapted to each other in the contiguous vertebrae, as to form a round hole in each side between each two vertebrae, through which the nerves that proceed from the spinal marrow and its blood-vessels pass.

The articulations then of these true vertebrae are plainly double; for their bodies are joined by the intervening cartilage above described, and their oblique processes being tipped with cartilages, are so connected by their ligaments, as to allow a small degree of motion to all sides.

The true vertebrae serve to give us an erect posture; to allow sufficient and secure motion to the head, neck, and trunk of the body, and to support and defend the bowels, and other soft parts.

Though the true vertebrae agree in the general structure which we have hitherto described; yet because of several specialities proper to a particular number, they are commonly divided into three classes, viz. cervical, dorsal, and lumbar.

The cervical are the seven uppermost vertebrae; which are distinguished from the rest by these marks.—Their bodies are smaller and more solid than any others, and flattened on the fore-part, to make way for the oesophagus; or rather this flat figure is owing to the pressure of that pipe, and to the action of the longi colli and anterior recti muscles.—They are also flat behind, where small processes rise, to which the internal ligaments are fixed.—The upper surface of the body of each vertebra is made hollow, by a flanting thin process which is raised on each side:—The lower surface is also excavated, but in a different manner; for here the posterior edge is raised a little, and the one before is produced a considerable way.—Hence we see how the cartilages between those bones are firmly connected, and their articulations are secure.

The cartilages between these vertebrae are thick, especially at their fore-part; which is one reason why the vertebrae advance forward as they descend, and have larger motion.

The oblique processes of these bones of the neck more justly deserve that name than those of any other vertebrae. They are situated flanting; the upper ones having their smooth and almost flat surfaces facing obliquely backwards and upwards, while the inferior oblique processes have their surfaces facing obliquely forwards and downwards.

The transverse processes of these vertebrae are framed in a different manner from those of any other bones of the spine: For besides the common transverse process rising from between the oblique processes of each side, there is a second one that comes out from the side of the body of each vertebra; and these two processes, after leaving a circular hole for the passage of the cervical artery and vein, unite, and are considerably hollowed at their upper part, with rising sides, to protect the nerves that pass in the hollow; and at last each side terminates in an obtuse point, for the insertion of muscles.

The spinal processes of these cervical bones stand nearly straight backwards, are shorter than those of any other vertebrae, and are forked or double at their ends; and hence allow a more convenient insertion to muscles.

So far most of the cervical vertebrae agree; but they have some particular differences, which oblige us to consider them separately.

The first, from its use of supporting the head, has the name of atlas; and is also called epistrophea, from the motion it performs on the second.

The atlas, contrary to all the other vertebrae of the spine, has no body; but, instead of it, there is a bony arch.—In the convex fore-part of which, a small rising appears, where the musculi longi colli are inserted; and, on each side of this protuberance, a small cavity may be observed, where the recti interni minores take their rise.—The upper and lower parts of the arch are rough and unequal, where the ligaments that connect

connect this vertebra to the os occipitis, and to the second vertebra, are fixed.—The back-part of the arch is concave, smooth, and covered with a cartilage, in a recent subject, to receive the tooth-like process of the second vertebra.—In a first vertebra, from which the second has been separated, this hollow makes the passage for the spinal marrow to seem much larger than it really is: On each side of it a small rough sinuosity may be remarked, where the ligaments going to the sides of the tooth-like process of the following vertebra are fastened; and on each side, a small rough protuberance and depression is observable, where the transverse ligament, which secures the tooth-like process in the sinuosity, is fixed, and hinders that process from injuring the medulla spinalis in the flexions of the head.

The atlas has as little spinal process as body; but instead thereof, there is a large bony arch, that the muscles which pass over this vertebra at that place might not be hurt in extending the head.

The superior oblique processes of this atlas are large, oblong, hollow, and more horizontal than in any other vertebra.—They rise more in their external than internal brim; by which their articulations with the condylloid of the os occipitis are firmer.—Under the external edge of each of these oblique processes, is the fossa, or deep open channel, in which the vertebral arteries make the circular turn, as they are about to enter the great foramen of the occipital bone, and where the tenth pair of nerves goes out.—The inferior oblique processes extending from within outwards and downwards, are large, concave, and circular. So that this vertebra, contrary to the other six, receives the bones with which it is articulated both above and below.

The transverse processes here are not much hollowed or forked, but are longer and larger than those of any other vertebra of the neck, for the origin and insertion of several muscles.

The hole for the spinal marrow is larger in this than in any other vertebra, not only on account of the marrow being largest here, but also to prevent its being hurt by the motions of this vertebra on the second one.—This large hole, and the long transverse processes, make this the broadest vertebra of the neck.

The condyles of the os occipitis move forwards and backwards in the superior oblique processes of this vertebra; but from the figure of the bones forming these joints, it appears, that very little motion can here be allowed to either side; and there must be still less circular motion.

The second vertebra colli is called dentata, from the tooth-like process on the upper part of its body.

The body of this vertebra is somewhat pyramidal, being large, and produced downwards, especially at its fore-side, to enter into a hollow of the vertebra below; while the upper part has a square process with a small point standing out from it. This it is that is imagined to resemble a tooth, and has given name to the vertebra.—The side of this process, on which the hollow of the anterior arch of the first vertebra plays, is convex, smooth, and covered with a cartilage; and it is of the same form behind, for the ligament, which is extended

transversely from one rough protuberance of the first vertebra to the other, and is cartilaginous in the middle, to move on it.

The superior oblique processes of this vertebra dentata are large, circular, very nearly in an horizontal position, and slightly convex, to be adapted to the inferior oblique processes of the first vertebra.

The transverse processes of the vertebra dentata are short, very little hollowed at their upper part, and not forked at their ends; and the canals through which the cervical arteries pass, are reflected outwards about the middle substance of each process; so that the course of these vessels may be directed towards the transverse processes of the first vertebra.

The spinal process of this vertebra tendata is thick, strong, and short, to give sufficient origin to the musculi recti maiores, and obliqui inferiores, and to prevent the contusion of these and other muscles in pulling the head back.

The third vertebra of the neck is by some called axis; but this name is applied to it with much less reason than to the second.—This third, and the three below, have nothing particular in their structure; but all their parts come under the general description formerly given, each of them being larger as they descend.

The seventh vertebra of the neck is near to the form of those of the back, having the upper and lower surfaces of its body less hollow than the others:—The oblique processes are more perpendicular;—neither spinal nor transverse processes are forked.—This seventh and the sixth vertebra of the neck have the hole in each of their transverse processes, more frequently divided by a small cross bridge, that goes between the cervical vein and artery, than any of the other vertebrae.

The twelve dorsal may be distinguished from the other vertebrae of the spine by the following marks.

Their bodies are of a middle size, betwixt those of the neck and loins;—they are more convex before than either of the other two sorts; and are flattened laterally by the pressure of the ribs, which are inserted into small cavities formed in their sides. This flattening on their sides, which makes the figure of these vertebrae almost an half oval, is of good use; as it affords a firm articulation to the ribs, allows the trachea arteria to divide at a small angle, and the other large vessels to run secure from the action of the vital organs.—These bodies are more concave behind than any of the other two classes.—Their upper and lower surfaces are horizontal.

The cartilages interposed between the bodies of these vertebrae are thinner than in any other of the true vertebrae; and contribute to the concavity of the spine in the thorax, by being thinnest at their fore-part.

The oblique processes are placed almost perpendicular; the upper ones slanting but a little forwards, and the lower ones slanting as much backwards.—They have not as much convexity or concavity as is worth remarking.—Between the oblique processes of opposite sides, several sharp processes stand out from the upper and lower parts of the plates which join to form the spinal process; into these sharp processes strong ligaments are fixed, for connecting the vertebrae.

The transverse processes of the dorsal vertebrae are long, thicker at their ends than in the middle, and turned obliquely backwards.

The spinal processes are long, small pointed, and sloping downwards and backwards; from their upper and back-part a ridge rises, which is received by a small channel in the fore-part of the spinal process immediately above, which is here connected to it by a ligament.

The conduit of the spinal marrow is here more circular, but, corresponding to the size of that cord, is smaller than in any of the other vertebrae, and a larger share of the holes in the bony bridges, for the transmission of the nerves, is formed in the vertebra above, than in the one below.

The connection of the dorsal vertebrae to the ribs, the thinness of their cartilages, the erect situation of the oblique processes, the length, sloping, and connection of the spinal processes, all contribute to restrain these vertebrae from much motion, which might disturb the actions of the heart and lungs; and, in consequence of the little motion allowed here, the intervertebral cartilages sooner shrivel, by becoming more solid: And therefore, the first remarkable curvature of the spine observed, as people advance to old age, is in the least stretched vertebrae of the back; or old people first become round-shouldered.

The bodies of the four uppermost dorsal vertebrae deviate from the rule of the vertebrae, becoming larger as they descend; for the first of the four is the largest, and the other three below gradually become smaller, to allow the trachea and large vessels to divide at smaller angles.

The two uppermost vertebrae of the back, instead of being very prominent forwards, are flattened by the action of the musculi longi colli and recti maiores.

The proportional size of the two little depressions in the body of each vertebra, for receiving the heads of the ribs, seems to vary in the following manner; the depression on the upper edge of each vertebra decreases as far down as the fourth, and after that increases.

The transverse processes are longer in each lower vertebra to the seventh or eighth, with their smooth surfaces, for the tubercles of the ribs, facing gradually more downwards; but afterwards, as they descend, they become shorter, and the smooth surfaces are directed more upwards.

The spinous processes of the vertebrae of the back become gradually longer and more slanting from the first, as far down as the eighth or ninth vertebra; from which they manifestly turn shorter and more erect.

The first vertebra, besides an oblong hollow in its lower edge, that assists in forming the cavity wherein the second rib is received, has the whole cavity for the head of the first rib formed in it.

The second has the name of axillary, without any thing particular in its structure.

The eleventh often has the whole cavity for the eleventh rib in its body, and wants the smooth surface on each transverse process.

The twelfth always receives the whole head of the last rib, and has no smooth surface on its transverse processes, which are very short. — The smooth surfaces of its inferior oblique processes face outwards as the lumbar do.

— And we may say in general, that the upper vertebrae of the back lose gradually their resemblance to those of the neck, and the lower ones come nearer to the figure of the lumbar.

The lowest order of the true vertebrae is the lumbar, which are five bones, that may be distinguished from any others by these marks: 1. Their bodies, though of a circular form at their fore-part, are somewhat oblong from one side to the other; which may be occasioned by the pressure of the large vessels, the aorta and cava, and of the viscera. The epiphyses on their edges are larger, and therefore the upper and lower surfaces of their bodies are more concave than in the vertebrae of the back. 2. The cartilages between these vertebrae are much the thickest of any, and render the spine convex within the abdomen, by their greatest thickness being at their fore-part. 3. The oblique processes are strong and deep; those in opposite sides being almost placed in parallel planes; the superior, which are concave, facing inwards, and the convex inferior ones facing outwards; and therefore each of these vertebrae receives the one above it, and is received by the one below; which is not so evident in the other two classes already described. 4. Their transverse processes are small, long, and almost erect, for allowing large motion to each bone, and sufficient insertion to muscles, and for supporting and defending the internal parts. 5. Betwixt the roots of the superior oblique and transverse processes, a small protuberance may be observed, where some of the muscles that raise the trunk of the body are inserted. 6. Their spinal processes are strong, straight, and horizontal, with broad flat sides, and a narrow edge above and below; this last being depressed on each side by muscles. And at the root of these edges, we see rough surfaces for fixing the ligaments. 7. The canal for the numerous cords, called cauda equina, into which the spinal marrow divides, is rather larger in these bones than what contains that marrow in the vertebrae of the back. 8. The holes for the passage of the nerves are more equally formed out of both the contiguous vertebrae than in the other classes; the upper one furnishes however the larger share of each hole.

The thick cartilages between these lumbar vertebrae, their deep oblique processes, and their erect spinal processes, are all fit for allowing large motion; though it is not so great as what is performed in the neck; which appears from comparing the arches which the head describes when moving on the neck, or the loins only.

The lumbar vertebrae, as they descend, have their oblique processes at a greater distance from each other, and facing more backwards and forwards.

Both transverse and spinal processes of the middlemost vertebrae of the loins are longest and thickest; in the vertebrae above and below they are less: so that these processes of the first and fifth are the least, to prevent their striking on the ribs or ossa ilium, or their bruising the muscles in the motions of the spine.

The epiphyses round the edges of the bodies of the lumbar vertebrae are most raised in the two lowest, which consequently make them appear hollower in the middle than the others are.

The body of the fifth vertebra is rather thinner than that of the fourth.—The spinal process of this fifth is smaller, and the oblique processes face more backwards and forwards than in any other lumbar vertebra.

The FALSE VERTEBRÆ compose the under pyramid of the spine. They are distinguished from the bones already described justly enough by this epithet of false; because, though each bone into which they can be divided in young people, resembles the true vertebrae in figure, yet none of them contribute to the motion of the trunk of the body; they being intimately united to each other in adults, except at their lower part, where they are moveable; whence they are commonly divided into two bones, os sacrum and coccygis.

OS SACRUM, is so called from being offered in sacrifice by the ancients, is of an irregular triangular shape, broad above, narrow below, convex behind, for the advantageous origin of the muscles that move the spine and thigh backwards; and concave behind, for enlarging the cavity of the pelvis.—Four transverse lines of a colour different from the rest of the bone, which are seen on its fore-part, are the marks of division of the five different bones of which it consists in young persons.

The fore-part of the os sacrum is smooth and flat, to allow a larger space for the contained bowels, without any danger of hurting them.—The back-part of it is almost straight, without so large a cavity as the vertebrae have.—The bridges between the bodies and processes of this bone, are much thicker, and in proportion shorter, than in the former class of bones.—The strength of these cross-bridges is very remarkable in the three upper bones, and is well-proportioned to the incumbent weight of the trunk of the body, which these bridges sustain in a transverse, consequently an unfavourable, situation, when the body is erect.

There are only two oblique processes of the os sacrum; one standing out on each side from the upper part of the first bone.—Their plain erect surfaces face backwards, and are articulated with the inferior oblique processes of the last vertebra of the loins, to which each of these processes is connected by a strong ligament, which rises from a feathery cavity round their roots, where mucilaginous glands are also lodged.—Instead of the other oblique processes of this bone, four rough tubercles are to be seen on each side of its surface behind, from which the musculus sacer has its origin.

The transverse processes here are all grown together into one large strong oblong process on each side; which, so far as it answers to the first three bones, is very thick, and divided into two irregular cavities, by a long perpendicular ridge.—The foremost of the two cavities has commonly a thin cartilaginous skin covering it in the recent subject, and is adapted to the unequal protuberance of the os ilium, and a strong ligament connects the circumference of these surfaces of the two bones.—The cavity behind is divided by a transverse ridge into two, where strong ligamentous strings that go from this bone to the os ilium, with a cellular substance containing muscles, are lodged.

The transverse processes of the two last bones of the

os sacrum are much smaller than the former.—At their back-part, near their edge, a knob and oblong flat surface give rise to two strong ligaments which are extended to the os ischium; and are therefore called sacro-sciatic.

The spinal processes of the three uppermost bones of the os sacrum appear short, sharp, and almost erect, while the two lower ones are open behind; and sometimes a little knob is to be seen on the fourth, though generally it is bifurcated, without the two legs meeting into a spine; in which condition also the first is often to be seen. The musculus latissimus, and longissimus dorsi, sacrolumbalis, and gluteus maximus, have part of their origins from these spinal processes.

The canal between the bodies and processes of this bone, for the cauda equina, is triangular; and becomes smaller as it descends, as the cauda also does.—Below the third bone, this passage is no more a complete bony canal, but is open behind; and is only there defended by a strong ligamentous membrane stretched over it, which, with the muscles that cover it, and are very prominent on each side, is a sufficient defence for the bundle of nerves within.

At the root of each oblique process of this bone, the notch is conspicuous, by which, and such another in the last vertebra of the loins, a passage is left for the twenty-fourth spinal nerve; and, in viewing the os sacrum, either before or behind, four large holes appear in each side, in much the same height, as where the marks of the union of its several bones remain. Some of the largest nerves of the body pass through the anterior holes; and superficial grooves running outwards from them in different directions, shew the course of these nerves.—From the intervals of these grooves, the pyriformis muscle chiefly rises.—The holes in the back-part of the bone are covered by membranes which allow small nerves to pass through them.—The two uppermost of these holes, especially on the fore-side, are the largest; and as the bone descends, the holes turn smaller. Sometimes a notch is only formed at the lower part in each side of this bone; and in other subjects there is a hole common to it and the os coccygis, through which the twenty-ninth pair of spinal nerves passes; and frequently a bony bridge is formed on the back-part of each side by a process sent up from the back-part of the os coccygis, and joined to the little knobs which the last bone of the os sacrum has instead of a spinal process. Under this bridge or jugum, the twenty-ninth pair of spinal nerves runs in its course to the common holes just now described.

The substance of the os sacrum is very spongy, without any considerable solid external plates, and is lighter proportionally to its bulk than any other bone in the body; but is secured from injuries by the thick muscles that cover it behind, and by the strong ligamentous membranes that closely adhere to it.

This bone is articulated above to the last vertebra of the loins, in the manner that the lumbar vertebrae are joined; and therefore the same motions may be performed here.—The articulation of the lower part of the os sacrum to the os coccygis seems well enough adapted for allowing

allowing considerable motion to this last bone, was it not much confined by ligaments. Laterally, the os sacrum is joined to the ossa ilium by an immovable synchondrosis.

The uses of the os sacrum are, to serve as the common base and support of the trunk of the body, to guard the nerves proceeding from the end of the spinal marrow, to defend the back-part of the pelvis, and to afford sufficient origin to the muscles which move the trunk and thigh.

Os COCCYGIS, or rump-bone, is that triangular chain of bones depending from the os sacrum; each bone becoming smaller as they descend, till the last ends almost in a point. The os coccygis is convex behind, and concave before; from which crooked pyramidal figure, which was thought to resemble a cuckow's beak, it has got its name.

This bone consists of four pieces in people of middle age:—In children, very near the whole of it is cartilage: In old subjects, all the bones are united, and become frequently one continued bone with the os sacrum.

The highest of the four bones is the largest, with shoulders extended farther to each side than the end of the os sacrum;—the upper surface of this bone is a little hollow.—From the back of that bulbous part called its shoulders, a process often rises up on each side, to join with the bifurcated spine of the fourth and fifth bones of the os sacrum, to form the bony bridge mentioned in the description of the os sacrum.—Immediately below the shoulders of the os coccygis, a notch may be remarked in each side, where the thirtieth pair of the spinal nerves passes.—The lower end of this bone is formed into a small head, which very often is hollow in the middle.

The three lower bones gradually become smaller, and are spongy; but are strengthened by a strong ligament which covers and connects them.—Their ends, by which they are articulated, are formed in the same manner as those of the first bone are.

The lower end of the fourth bone terminates in a rough point, to which a cartilage is appended.

To the sides of these bones of the os coccygis, the coccygei muscles, and part of the levatores ani, and of the glutei maximi, are fixed.

The os coccygis serves to sustain the intestinum rectum; and, in order to perform this office more effectually, it is made to turn with a curve forwards; by which also the bone itself, as well as the muscles and teguments, is preserved from any injury, when we sit with our body reclined back.

The second part of the trunk of the skeleton, the PELVIS, is the cylindrical cavity at the lower part of the abdomen, formed by the os sacrum, os coccygis, and ossa innominata; which last therefore fall now in course to be examined.

The OSSA INNOMINATA are two large broad bones, which form the fore-part and sides of the pelvis, and the lower part of the sides of the abdomen.—In children each of these bones is evidently divided into three; which are afterwards so intimately united, that scarce

the least mark of their former separation remains: notwithstanding, they are described as consisting each of three bones, to wit, the os ilium, ischium, and pubis.

Os ILIUM, or haunch-bone, is situated highest of the three, and reaches as far down as one third of the great cavity into which the head of the thigh-bone is received.

The external side of this bone is unequally convex, and is called its dorsum;—the internal concave surface is by some (but improperly) named costa.—The semicircular edge at the highest part of this bone, which is tipped with a cartilage in the recent subject, is named the spine, into which the external or descending oblique muscle of the abdomen is inserted; and from it the internal ascending oblique and the transverse muscles of the belly, with the gluteus maximus, quadratus lumborum, and latissimus dorsi, have their origin.—The ends of the spine are more prominent than the surface of the bone below them; therefore are reckoned processes.—From the anterior spinal process, the sartorius and fascialis muscles have their rise, and the outer end of the doubled tendon of the external oblique muscle of the abdomen, commonly called Fallopis's or Poupart's ligament, is fixed to it.—The inside of the posterior spinal process, and of part of the spine forward from that, is made flat and rough where the sacro-lumbalis and longissimus dorsi rise; and to its outside ligaments, extended to the os sacrum and transverse processes of the fifth and fourth vertebrae of the loins, are fixed.—Below the anterior spinal process another protuberance stands out, which, by its situation, may be distinguished from the former, by adding the epithet of inferior, where the musculus rectus tibiae has its origin.—Betwixt these two anterior processes the bone is hollowed where the beginning of the sartorius muscle is lodged.—Below the posterior spinal processes, a second protuberance of the edge of this bone is in like manner observable, which is closely applied to the os sacrum.—Under this last process a considerable large niche is observable in the os ilium; between the sides of which and the strong ligament that is stretched over from the os sacrum to the sharp-pointed process of the os ischium of the recent subject, a large hole is formed, through which the musculus pyiformis, the great sciatic nerve, and the posterior crural vessels, pass, and are protected from compression.

The external broad side, or dorsum of the os ilium, is a little hollow towards the fore part; farther back it is as much raised; then is considerably concave; and, lastly, it is convex. These inequalities are occasioned by the actions of the muscles that are situated on this surface.—From behind the uppermost of the two anterior spinal processes, in such bones as are strongly marked by the muscles, a semicircular ridge is extended to the hollow passage of the sciatic nerve. Between the spine and this ridge, the gluteus medius takes its rise. Immediately from above the lowest of the anterior spinal processes, a second ridge is stretched to the niche. Between this and the former ridge, the gluteus minimus has its origin.—On the outside of the posterior spinal processes, the dorsum of the os ilium is flat and rough, where part of the musculus gluteus maximus and pyiformis rises.—The lowest part of this bone is the thickest, and is formed into a large

large cavity with high brims, to assist in composing the great acetabulum.

The internal surface of the os ilium is concave in its broadest fore part, where the internal iliac muscle has its origin, and some share of the intestinum ilium and colon is lodged.——From this large hollow, a small sinuosity is continued obliquely forwards, at the inside of the anterior inferior spinal process, where part of the psoas and iliacus muscles, with the crural vessels and nerves, pass.——The large concavity is bounded below by a sharp ridge, which runs from behind forwards, and, being continued with such another ridge of the os pubis, forms a line of partition between the abdomen and pelvis.——Into this ridge the broad tendon of the psoas parvus is inserted.

All the internal surface of the os ilium, behind this ridge, is very unequal: For the upper part is flat, but spongy, where the sacro-lumbalis and longissimus dorsi rise.——Lower down, there is a transverse ridge from which ligaments go out to the os sacrum.——Immediately below this ridge, the rough unequal cavities and prominences are placed, which are exactly adapted to those described on the side of the os sacrum.——In the same manner, the upper part of this rough surface is porous, for the firmer adhesion of the ligamentous cellular substance; while the lower part is more solid, and covered with a thin cartilaginous skin, for its immovable articulation with the os sacrum.

Os ICHIUM, or bip-bone, is of a middle bulk between the two other parts of the os innominatum, is situated lowest of the three, and is of a very irregular figure.——Its extent might be marked by an horizontal line drawn near through the middle of the acetabulum; for the upper bulbous part of this bone forms some less than the lower half of that great cavity, and the small leg of it rises to much the same height on the other side of the great hole common to this bone and the os pubis.

From the upper thick part of the os ischium, a sharp process, called by some spinous, stands out backwards, from which chiefly the musculus coccygeus and superior gemellus, and part of the levator ani, rise; and the anterior or internal sacrosciatic ligament is fixed to it.——Immediately below this process, a sinuosity is formed for the tendon of the musculus obturator internus.——In a recent subject, this part of the bone, which serves as a pulley on which the obturator muscle plays, is covered with a ligamentous cartilage, that, by two or three small ridges, points out the interstices of the fibres in the tendon of this muscle.——The outer surface of the bone at the root of this spinous process is made hollow by the pyriformis, or iliacus externus muscle.

Below the sinuosity for the obturator muscle, is the great knob or tuberosity, covered with cartilage or tendon.——The upper part of the tuberosity gives rise to the inferior gemellus muscle.——To a ridge at the inside of this, the external or posterior sacrosciatic ligament is so fixed, that between it, the internal ligament, and the sinuosity of the os ischium, a passage is left for the internal obturator muscle.——The upper thick smooth part of the tuber, called by some its dorsum, has two oblique impressions on it. The inner one gives origin to

the long head of the biceps flexor tibiae and feminervosus muscles, and the femimembranosus rises from the exterior one, which reaches higher and nearer the acetabulum than the other.——The lower, thinner, more scabrous part of the knob which bends forwards, is also marked with two flat surfaces, whereof the internal is what we lean upon in sitting, and the external gives rise to the largest head of the triceps adductor femoris.——Between the external margin of the tuberosity, and the great hole of the os innominatum, there is frequently an obtuse ridge extended down from the acetabulum, which gives origin to the quadratus femoris.——As the tuber advances forwards, it becomes smaller, and is rough, for the origin of the musculus transversalis and erector penis.——The small leg of it, which mounts upwards to join the os pubis, is rough and prominent at its edge, where the two lower heads of the triceps or quadriceps adductor femoris take their rise.

The upper and back part of the os ischium is broad and thick; but its lower and fore-part is narrower and thinner.

The os ilium and pubis of the same side are the only bones which are contiguous to the os ischium.

The Os PUBIS, or share-bone, is the least of the three parts of the os innominatum, and is placed at the upper fore-part of it.——The thick largest part of this bone is employed in forming the acetabulum; from which, becoming much smaller, it is stretched inwards to its fellow of the other side, where again it grows larger, and sends a small branch downwards to join the end of the small leg of the os ischium.——The upper fore-part of each os pubis is tuberculous and rough where the musculus rectus and pyramidalis are inserted.——From this a ridge is extended along the upper edge of the bone, in a continued line with such another of the os ilium, which divides the abdomen and pelvis. The ligament of Fallopius is fixed to the internal end of this ridge, and the smooth hollow below it is made by the psoas and iliacus internus muscles passing with the anterior crural vessels and nerves behind the ligament.——Some way below the former ridge, another is extended from the tuberculous part of the os pubis downwards, and outwards towards the acetabulum; between these two ridges the bone is hollow and smooth, for lodging the head of the pectineus muscle.——Immediately below, where the lower ridge is to take the turn downwards, a winding notch is made, which is comprehended in the great foramen of a skeleton, but is formed into a hole by a subtended ligament in the recent subject, for the passage of the posterior crural nerve, an artery, and a vein.——The internal end of the os pubis is rough and unequal, for the firmer adhesion of the thick ligamentous cartilage that connects it to its fellow of the other side.——The process which goes down from that to the os ischium is broad and rough before, where the gracilis and upper heads of the triceps, or rather quadriceps adductor femoris, have their origin.

Betwixt the os ischium and pubis a very large irregular hole is left, which, from its resemblance to a door or shield, has been called thyroides. This hole is all, except the notch for the posterior crural nerve, filled up, in a recent subject, with a strong ligamentous membrane, that

that adheres very firmly to its circumference. From this membrane chiefly the two obturator muscles, external and internal, take their rise.—The great design of this hole, besides rendering the bone lighter, is to allow a strong enough origin to the obturator muscles, and sufficient space for lodging their bellies, that there may be no danger of disturbing the functions of the contained viscera of the pelvis by the actions of the internal, nor of the external being bruised by the thigh-bone, especially by its lesser trochanter, in the motions of the thigh inwards.—The bowels sometimes make their way through the nitch for the vessels, at the upper part of this thyroid hole, which causes a hernia in this place.

In the external surface of the ossa innominata, near the outside of the great hole, a large deep cavity is formed by all the three bones conjointly: For the os pubis constitutes about one fifth; the os ilium makes something less than two fifths, and the os ischium as much more than two fifths. The brims of this cavity are very high, and are still much more enlarged by the ligamentous cartilage, with which they are tipped in a recent subject. From this form of the cavity it has been called acetabulum; and, for a distinguishing character, the name of the bone that constitutes the largest share of it is added; therefore acetabulum ossis ischii is the name this cavity commonly bears.—Round the base of the supercilia the bone is rough and unequal, where the capsular ligament of the articulation is fixed.—The brims at the upper and back-part of the acetabulum are much larger and higher than any where else; which is very necessary to prevent the head of the femur from slipping out of its cavity at this place, where the whole weight of the body bears upon it, and consequently would otherwise be constantly in danger of thrusting it out.—As these brims are extended downwards and forwards, they become less; and at their internal lower part a breach is made in them; from the one side of which to the other, a ligament is placed in the recent subject; under which a large hole is left, which contains a fatty cellular substance and vessels.—Besides this difference in the height of the brims, the acetabulum is otherwise unequal: For the lower internal part of it is depressed below the cartilaginous surface of the upper-part, and is not covered with cartilage; into the upper-part of this particular depression, where it is deepest and of a semilunar form, the ligament of the thigh-bone, commonly called the round one, is inserted; while in its more superficial lower part the large mucilaginous gland of this joint is lodged. The largest share of this separate depression is formed in the os ischium.

The ossa innominata are joined at their back-part to each side of the os sacrum by a sort of future, with a very thin intervening cartilage, which serves as so much glue to cement these bones together; and strong ligaments go from the circumference of this unequal surface to connect them more firmly. The ossa innominata are connected together at their fore-part by the ligamentous cartilage interposed between the two ossa pubis.—These bones can therefore have no motion in a natural state, except what is common to the trunk of the body, or to the os sacrum.

Each os innominatum affords a socket (the acetabulum) for the thigh-bones to move in, and the trunk of the body rolls here so much on the heads of the thigh-bones, as to allow the most conspicuous motions of the trunk, which are commonly thought to be performed by the bones of the spine.

The pelvis then has a large open above where it is continued with the abdomen, is strongly fenced by bones on the sides, back, and fore-part, and appears with a wide opening below, in the skeleton; but, in the recent subject, a considerable part of the opening is filled by the sacroiliac ligaments, pyriform, internal obturator, levatores ani, gemini, and coccygei muscles, which support and protect the contained parts better than bones could have done; so that space is only left at the lowest part of it, for the large excretories, the vesica urinaria, intestinum rectum, and in females, the uterus, to discharge themselves.

The THORAX, or chest, reaches from below the neck to the belly; and, by means of the bones that guard it, is formed into a large cavity: The figure of which is somewhat conoidal.

The bones which form the thorax are the twelve dorsal vertebrae behind, the ribs on the sides, and the sternum before.

The vertebrae have already been described as part of the spine.

The RIBS, or costæ, (as if they were custodes, or guards, to those principal organs of the animal machine, the heart and lungs), are the long crooked bones placed at the side of the chest, in an oblique direction downwards in respect of the back-bone.—Their number is generally twelve on each side; though frequently eleven or thirteen have been found.

The ribs are all concave internally; where they are also made smooth by the action of the contained parts, which, on this account, are in no danger of being hurt by them; and they are convex externally, that they might resist that part of the pressure of the atmosphere, which is not balanced by the air within the lungs, during inspiration.—The ends of the ribs next the vertebrae are rounder than they are after these bones have advanced forwards, when they become flatter and broader, and have an upper and lower edge, each of which is made rough by the action of the intercostal muscles, inserted into them.—The upper edge of the ribs is more obtuse and rounder than the lower, which is depressed on its internal side by a long fossa, for lodging the intercostal vessels and nerves; on each side of which there is a ridge, to which the intercostal muscles are fixed. The fossa is not observable however at either end of the ribs: for, at the posterior or root, the vessels have not yet reached the ribs; and, at the fore-end, they are split away into branches, to serve the parts between the ribs.

At the posterior end of each rib, a little head is formed, which is divided by a middle ridge into two plain or hollow surfaces; the lowest of which is the broadest and deepest in most of them. The two plains are joined to the bodies of two different vertebrae, and the ridge forces itself into the intervening cartilage.—

A little way from this head, we find, on the external surface, a small cavity, where mucilaginous glands are lodged; and round the head, the bone appears spongy, where the capsular ligament of the articulation is fixed. — Immediately beyond this a flattened tubercle rises, with a small cavity at, and roughness about its root, for the articulation of the rib with the transverse process of the lowest of the two vertebrae, with the bodies of which the head of the rib is joined. — Advancing further on this external surface, we observe in most of the ribs another smaller tubercle, into which ligaments which connect the ribs to each other, and to the transverse processes of the vertebrae, and portions of the longissimus dorsi, are inserted. — Beyond this the ribs are made flat by the sacro-lumbalis muscle, which is inserted into the part of this flat surface farthest from the spine, where each rib makes a considerable curve, called by some its angle. — Then the rib begins to turn broad, and continues so to its anterior end, which is hollow and spongy, for the reception of, and firm coalition with the cartilage that runs thence to be inserted into the sternum, or to be joined with some other cartilage.

To the fore-end of each rib a long broad and strong cartilage is fixed, and reaches thence to the sternum, or is joined to the cartilage of the next rib. This course, however, is not in a straight line with the rib; for generally the cartilages make a considerable curve, the concave part of which is upwards; therefore, at their insertion into the sternum, they make an obtuse angle above, and an acute one below. — These cartilages, as all others, are firmer and harder internally, than they are on their external surface.

The ribs then are articulated at each end, of which the one behind is doubly joined to the vertebrae; for the head is received into the cavities of two bodies of the vertebrae, and the larger tubercle is received into the depression in the transverse process of the lower vertebra.

Hitherto we have laid down the general structure and connection of the ribs, and shall next mark their differences.

In viewing the ribs from above downwards, their figure is still straighter; the uppermost being the most crooked of any. — Their obliquity, in respect of the spine, increases as they descend; so that though their distances from each other is very little different at their back-part, yet at their fore-ends the distances between the lower ones must increase.

The length of the ribs increases from the first and uppermost rib, as far down as the seventh; and from that to the twelfth, as gradually diminishes. — The superior of the two plain, or rather hollow surfaces, by which the ribs are articulated to the bodies of the vertebrae, gradually increases from the first to the fourth rib, and is diminished after that in each lower rib. — The distance of their angles from the heads always increases as they descend to the ninth, because of the greater breadth of the sacro-lumbalis muscle.

The ribs are commonly divided into true and false.

The true costæ are the seven upper ones of each side, whose cartilages are all gradually longer as the ribs descend, and are joined to the breast-bone; so that being pressed

constantly between two bones, they are flattened at both ends, and are thicker, harder, and more liable to ossify, than the other cartilages that are not subject to so much pressure. These ribs include the heart and lungs; and therefore are the proper or true custodes of life.

The five inferior ribs of each side are the false or bastard, whose cartilages do not reach to the sternum; and therefore, wanting the resistance at their fore-part, they are there pointed; and, on this account, having less pressure, their substance is softer. — The cartilages of these false ribs are shorter as the ribs descend. — To all these five ribs the circular edge of the diaphragm is connected; and its fibres, instead of being stretched immediately transversely, and so running perpendicular to the ribs, are pressed so as to be often, especially in expiration, parallel to the plane in which the ribs lie.

The first rib of each side is so situated, that the flat sides are above and below, while one edge is placed inwards, and the other outwards, or nearly so; therefore sufficient space is left above it for the subclavian vessels and muscle; and the broad concave surface is opposed to the lungs: But then, in consequence of this situation, the channel for the intercostal vessels is not to be found, and the edges are differently formed from all the other, except the second; the lower one being rounded, and the other sharp. — The head of this rib is not divided into two plain surfaces by a middle ridge, because it is only articulated with the first vertebra of the thorax. — Its cartilage is ossified in adults, and is united to the sternum at right angles. — Frequently this first rib has a ridge rising near the middle of its posterior edge, where one of the heads of the scalenus muscle rises. — Farther forward it is flattened, or sometimes depressed by the clavicle.

The fifth, sixth, and seventh, or rather the sixth, seventh, eighth, and sometimes the fifth, sixth, seventh, eighth, ninth ribs, have their cartilages at least contiguous; and frequently they are joined to each other by cross cartilages; and most commonly the cartilages of the eighth, ninth, tenth, are connected to the former, and to each other, by firm ligaments.

The eleventh, and sometimes the tenth rib, has no tubercle for its articulation with the transverse process of the vertebra, to which it is only loosely fixed by ligaments. — The fossa in its lower edge is not so deep as in the upper ribs, because the vessels run more towards the interstice between the ribs. — Its fore-end is smaller than its body, and its short small cartilage is but loosely connected to the cartilage of the rib above.

The twelfth rib is the shortest and straightest. — Its head is only articulated with the last vertebra of the thorax; therefore is not divided into two surfaces. — This rib is not joined to the transverse process of the vertebra, and therefore has no tubercle, being often pulled necessarily inwards by the diaphragm, which an articulation with the transverse process would not have allowed. — The fossa is not found at its under edge, because the vessels run below it. — The fore-part of this rib is smaller than its middle, and has only a very small-pointed cartilage fixed to it. — To its whole internal side the diaphragm is connected.

The STERNUM, or breast-bone, is the broad flat bone or pile of bones, at the fore-part of the thorax.—In adults of a middle age, it is composed of three bones, which easily separate after the cartilages connecting them are destroyed. Frequently the two lower bones are found intimately united; and very often in old people, the sternum is a continued bony substance from one end to the other; though we still observe two, sometimes three, transverse lines on its surface; which are marks of the former divisions.

When we consider the sternum as one bone, we find it broadest and thickest above, and becoming smaller as it descends. The internal surface of this bone is somewhat hollowed for enlarging the thorax; but the convexity on the external surface is not so conspicuous, because the sides are pressed outwards by the true ribs; the round heads of whose cartilages are received into seven smooth pits, formed in each side of the sternum, and are kept firm there by strong ligaments, which, on the external surface, have a particular radiated texture.—The pits at the upper part of the sternum are at the greatest distance one from another, and, as they descend, are nearer; so that the two lowest are contiguous.

The first of the three bones that compose the sternum, all agree, is somewhat of the figure of a heart, as it is commonly painted; only it does not terminate in a sharp point.—This is the uppermost thickest part of the sternum.

The upper middle part of this first bone, where it is thickest, is hollowed, to make place for the trachea arteria; though this cavity is principally formed by the bone being raised on each side of it, partly by the clavicles thrusting it inwards, and partly by the sterno-mastoidei muscles pulling it upwards.—On the outside of each tubercle, there is an oblong cavity, that, in viewing it transversely from before backwards, appears a little convex: Into these glens the ends of the clavicles are received.—In the side of the under end of this first bone, the half of the pit for the second rib on each side is formed.—The upper part of the surface behind is covered with a strong ligament, which secures the clavicles.

The second or middle division of this bone, is much longer, narrower, and thinner than the first; but, excepting that it is a little narrower above than below, it is nearly equal all over in its dimensions of breadth or thickness.—In the sides of it are complete pits for the third, fourth, fifth, and sixth ribs, and an half of the pits for the second and seventh.

The third bone is much less than the other two, and has only one half of the pit for the seventh rib formed in it; wherefore it might be reckoned only an appendix of the sternum.—In young subjects it is always cartilaginous, and is better known by the name of cartilago xiphoides, or eniformis, than any other; though the ancients often called the whole sternum ensiforme.—This third bone is seldom of the same figure, magnitude, or situation in any two subjects; for sometimes it is a plain triangular bone, with one of the angles below, and perpendicular to the middle of the upper side, by which it is connected to the second bone.—In other people, the

point is turned to one side, or obliquely forwards or backwards.—Frequently it is all nearly of an equal breadth, and in several subjects it is bifurcated; whence some writers give it the name of furcella, or furcula inferior; or else it is unossified in the middle.—In the greatest number of adults it is ossified, and tipped with a cartilage; in some, one half of it is cartilaginous; and in others, it is all in a cartilaginous state.—Generally several oblique ligaments, fixed at one end to the cartilages of the ribs, and by the other to the outer surface of the xiphoid-bone, connect it firmly to those cartilages.

The uses of the sternum are, to afford origin and insertion to several muscles; to sustain the mediastinum, to defend the vital organs, the heart and lungs, at the fore-part; and, lastly, by serving as a moveable fulcrum of the ribs, to assist considerably in respiration.

OF THE SUPERIOR EXTREMITIES.

EACH superior extremity is divided into the shoulder, arm, fore-arm, and hand.

The SHOULDER consists of the clavicle and scapula. CLAVICULA, or collar-bone, is the long crooked bone, in figure like an Italic s, placed almost horizontally between the upper lateral part of the sternum, and what is commonly called the top of the shoulder, which, as a clavus or beam, it bears off from the trunk of the body.

The clavicle, as well as other long round bones, is larger at its two ends than in the middle. The end next to the sternum is triangular: The angle behind is considerably produced, to form a sharp ridge, to which the transverse ligament extended from one clavicle to the other is fixed.—The side opposite to this is somewhat rounded.—The middle of this protuberant end is as irregularly hollowed, as the cavity in the sternum for receiving it is raised; but, in a recent subject, the irregular concavities of both are supplied by a moveable cartilage, which is not only much more closely connected every where, by ligaments, to the circumference of the articulation, than those of the lower jaw are; but it grows to the two bones at both its internal and external ends; its substance at the internal end being soft, but very strong, and resembling the intervertebral cartilages.

From this internal end the clavicle, for about two fifths of its length, is bended obliquely forwards and downwards. On the upper and fore-part of this curvature a small ridge is seen, with a plain rough surface before it; whence the musculus sterno-hyoides and sterno-mastoideus have in part their origin.—Near the lower angle, a small plain surface is often to be remarked, where the first rib and this bone are contiguous, and are connected by a firm ligament.—From this a rough plain surface is extended outwards, where the pectoral muscle has part of its origin.—Behind, the bone is made flat and rough by the insertion of the larger share of the subclavian muscle.—After the clavicle begins to be bended backwards, it is round, but soon after becomes broad and thin; which shape it retains to its external end.—Along the external concavity, a rough sinuosity runs, from which some part of the deltoid muscle takes its rise:—Opposite to this, on the convex edge, a scabrous ridge

ridge gives insertion to a fibre of the cucullaris muscle. The upper surface of the clavicle here is flat; but the lower is hollow, for lodging the beginning of the musculus subclavius; and towards its back-part a tubercle rises, to which, and a roughness near it, the strong short thick ligament connecting this bone to the coracoid process of the scapula is fixed.

The external end of this bone is horizontally oblong, smooth, sloping at the posterior side, and tipped in a recent subject with a cartilage, for its articulation with the acromion scapula.

The medullary arteries, having their direction obliquely outwards, enter the clavicles by one or more small passages in the middle of their back-part.

The triangular unequal interior end of each clavicle, has the cartilage above described interposed betwixt it and the irregular cavity of the sternum.—The ligaments, which surround this articulation to secure it, are so short and strong, that little motion can be allowed any way; and the strong ligament that is stretched across the upper furcula of the sternum, from the posterior prominent angle of the one clavicle, to the same place of the other clavicle, serves to keep each of these bones more firmly in their place.—By the assistance, however, of the moveable intervening cartilage, the clavicle can, at this joint, be raised or depressed, and moved backwards and forwards so much, as that the external end, which is at a great distance from that axis, enjoys very conspicuous motions.

The uses of the clavicles are, to keep the scapulae, and consequently all the superior extremities, from falling in and forward upon the thorax.

SCAPULA, or shoulder-blade, is the triangular bone situated on the outside of the ribs, with its longest side, called its base, towards the spinal processes of the vertebrae, and with the angle at the upper part of this side about three inches, and the lower angle at a greater distance from these processes.—The back-part of the scapula has nothing but the thin ends of the ferratus anticus major, and subscapularis muscles, between it and the ribs: But as this bone advances forwards, its distance from the ribs increases.—The upper, or shortest side, called the superior costa of the scapula, is nearly horizontal, and parallel with the second rib.—The lower side, which is named the inferior costa, is extended obliquely from the third to the eighth rib.—The inferior angle of the scapula is very acute; and the upper one is near to a right angle.—The body of this bone is concave towards the ribs, and convex behind, where it has the name of dorsum.—Three processes are generally reckoned to proceed from the scapula.—The first is the large spine that rises from its convex surface behind, and divides it unequally.—The second process stands out from the fore-part of the upper side; and, from its imaginary resemblance to a crow's beak, is named coracoides.—The third process is the whole thick bulbous fore-part of the bone.

After thus naming the several constituent parts of the scapula, the particular description will be more easily understood.

The base, which is tipped with cartilage, is not all

straight: For, above the spine, it runs obliquely forwards to the superior angle; that here it might not be too protuberant backwards, and so bruise the muscles and teguments: Into the oblique space the musculus patientie is inserted.—At the root of the spine, on the back-part of the base, a triangular plain surface is formed, by the pressure of the lower fibres of the trapezius.—Below this the edge of the scapula is scabrous and rough, for the insertion of the ferratus major anticus, and rhomboid muscles.

The back-part of the inferior angle is made smooth by the latissimus dorsi passing over it. This muscle also alters the direction of the inferior costa, some way forwards from this angle: and so far it is flattened behind by the origin of the teres major.—As the inferior costa advances forwards, it is of considerable thickness, is slightly hollowed and made smooth behind by the teres minor, while it has a fossa formed into it below by part of the subscapularis; and between the two a ridge, with a small depression, appears, where the longus extensor cubiti has its origin.

The superior costa is very thin; and near its fore-part there is a semilunar notch, from one end of which to the other a ligament is stretched; and sometimes the bone is continued, to form one, or sometimes two holes, for the passage of the scapular blood-vessels and nerves.—Immediately behind this semilunar cavity, the coraco-hyoid muscle has its rise.—From the notch, to the termination of the fossa for the teres minor, the scapula is narrower than any where else, and supports the third process. This part has the name of cervix.

The whole dorsum of the scapula is always said to be convex; but, by reason of the raised edges that surround it, it is divided into two cavities by the spine, which is stretched from behind forwards, much nearer to the superior than to the inferior costa.—The cavity above the spine is concave where the supra-spinatus muscle is lodged; while the surface of this bone below the spine, on which the infra-spinatus muscle is placed, is convex, except a fossa that runs at the side of the inferior costa.

The internal or anterior surface of this bone is hollow, except in the part above the spine, which is convex.—The subscapularis muscle is extended over this surface, where it forms several ridges and intermediate depressions, commonly mistaken for prints of the ribs; they point out the interstices of the bundles of fibres of which the subscapularis muscle is composed.

The spine rises small at the base of the scapula, and becomes higher and broader as it advances forwards.—On the sides it is unequally hollowed and crooked, by the actions of the adjacent muscles.—Its ridge is divided into two rough flat surfaces: Into the upper one, the trapezius muscle is inserted; and the lower one has part of the deltoid fixed to it.—The end of the spine, called acromion, or top of the shoulder, is broad and flat, and is sometimes only joined to the spine by a cartilage.—The anterior edge of the acromion is flat, smooth, and covered with a cartilage, for its articulation with the external end of the clavicle; and it is hollowed below, to allow a passage to the infra and supra-spinati muscles, and free motion to the os humeri.

The

The coracoid process is crooked, with its point inclining forwards; so that a hollow is left at the lower side of its root, for the passage of the infra-scapularis muscle. — The end of this process is marked with three plain surfaces. Into the internal, the serratus minor anticus is inserted: From the external, one head of the biceps flexor cubiti rises; and from the lower one, the coracobrachialis has its origin. — At the upper part of the root of this process, immediately before the femilunar cavity, a smooth tubercle appears, where a ligament from the clavicle is fixed. From all the external side of this coracoid apophyse, a broad ligament goes out, which becomes narrower where it is fixed to the acromion.

From the cervix scapule the third process is produced. The fore-part of this is formed into a glenoid cavity, which is of the shape of the longitudinal section of an egg, being broad below, and narrow above. — Between the brims of this hollow, and the fore-part of the root of the spine, a large sinuosity is left, for the transmission of the supra and infra-spinati muscles; and, on the upper part of these brims, we may remark a smooth surface, where the second head of the biceps flexor cubiti has its origin. — The root of the supercilia is rough all round, for the firmer adhesion of the capsular ligament of the articulation, and of the cartilage which is placed on these brims, where it is thick, but becomes very thin as it is continued towards the middle of the cavity, which it lines all over.

The medullary vessels enter the scapula near the base of the spine.

The scapula and clavicle are joined by plain surfaces, tipped with cartilage; by which neither bone is allowed any considerable motion, being tightly tied down by the common capsular ligament, and by a very strong one which proceeds from the coracoid process; but divides into two before it is fixed into the clavicle, with such a direction, as either can allow this bone to have a small rotation, in which its posterior edge turns more backwards, while the anterior one rises farther forwards; or it can yield to the fore-part of the scapula moving downwards, while the back-part of it is drawn upwards; in both which cases, the oblong smooth articulated surfaces of the clavicle and scapula are not in the same plane, but stand a little transversely, or across each other, and thereby preserve this joint from luxations, to which it would be subject, if either of the bones was to move on the other perpendicularly up and down, without any rotation. — The scapula is connected to the head, os hyoides, vertebrae, ribs, and arm-bone, by muscles, that have one end fastened to these bones, and the other to the scapula, which can move it upwards, downwards, backwards, or forwards; by the quick succession of these motions, its whole body is carried in a circle.

The use of the scapula is, to serve as a fulcrum to the arm; and, by altering its position on different occasions, to allow always the head of the os humeri a right situated socket to move in; and thereby to assist and to enlarge greatly the motions of the superior extremity, and to afford the muscles which rise from it more advantageous actions, by altering their directions to the bone which they are to move.

The ARM has only one bone, best known by the Latin name of os humeri; which is long, round, and nearly straight.

The upper end of this bone is formed into a large, round, smooth head, whose middle point is not in a straight line with the axis of the bone, but stands obliquely backwards from it. — The extent of the head is distinguished by a circular fossa surrounding its base, where the head is united to the bone, and the capsular ligament of the joint is fixed. — Below the fore-part of its base two tubercles stand out: The smallest one, which is situated most to the inside, has the tendon of the subscapularis muscle inserted into it. — The larger more external protuberance is divided, at its upper part, into three smooth plain surfaces; into the anterior of which, the musculus supra-spinatus; into the middle or largest, the infra-spinatus; into the one behind, the teres minor, is inserted. — Between these two tubercles, exactly in the fore part of the bone, a deep long fossa is formed, for lodging the tendinous head of the biceps flexor cubiti. — On each side of this fossa, as it descends in the os humeri, a rough ridge, gently flattened in the middle, runs from the roots of the tubercles. — The tendon of the pectoral muscle is fixed into the anterior of these ridges, and the latissimus dorsi, and teres major, are inserted into the internal one. — A little behind the lower end of this last, another rough ridge may be observed, where the coraco-brachialis is inserted. — From the back-part of the root of the largest tubercle, a ridge also is continued, from which the brevis extensor cubiti rises. — This bone is flattened on the inside, about its middle, by the belly of the biceps flexor cubiti. — In the middle of this plain surface, the entry of the medullary artery is seen flanting obliquely downwards. — At the fore-side of this plane, the bone rises in a sort of ridge, which is rough, and often has a great many small holes in it, where the tendon of the strong deltoid muscle is inserted; on each side of which the bone is smooth and flat, where the brachiocephalus intermusculus rises. The exterior of these two flat surfaces is the largest; behind it a superficial spiral channel, formed by the muscular nerve and the vessels that accompany it, runs from behind forwards and downwards. — The body of the os humeri is flattened behind by the extensors of the fore-arm. — Near the lower end of this bone, a large sharp ridge is extended on its outside, from which the musculus spinator radii longus, and the longest head of the extensor carpi radialis rise. — Opposite to this, there is another small ridge, to which the aponeurotic tendon, that gives origin to the fibres of the internal and external brachiocephalus muscles, is fixed; and from a little depression on the fore-side of it, the pronator radii teres rises.

The body of the os humeri becomes gradually broader towards the lower end, where it has several processes; at the roots of which there is a cavity before, and another behind. The anterior is divided, by a ridge, into two; the external, which is the least, receives the end of the radius; and the internal receives the coronoid process of the ulna in the section of the fore-arm, while the posterior deep triangular cavity lodges the olecranon in the extensions of that member. — The sides of the

the posterior cavity are stretched out into two processes, one on each side: These are called condyles; from each of which a strong ligament goes out to the bones of the fore-arm.—The external condyle, which has an oblique direction also forwards in respect of the internal, when the arm is in the most natural posture, is equally broad, and has an obtuse smooth head rising from it forwards.—From the rough part of the condyle, the inferior head of the bicornis, the extensor digitorum communis, extensor carpi ulnaris, anconeus, and some part of the supinator radii brevis, take their rise; and on the smooth head the upper end of the radius plays.—Immediately on the outside of this, there is a sinuosity made by the shorter head of the bicornis muscle, upon which the muscular nerve is placed.—The internal condyle is more pointed and protuberant than the external, to give origin to some part of the flexor carpi radialis, pronator radii teres, palmaris longus, flexor digitorum sublimis, and flexor carpi ulnaris.—Between the two condyles, is the trochlea or pulley, which consists of two lateral protuberances, and a middle cavity, that are smooth, and covered with cartilage.—When the fore-arm is extended, the tendon of the internal brachio-ulnaris muscle is lodged in the fore-part of the cavity of this pulley.—The external protuberance, which is less than the other, has a sharp edge behind; but forwards, this ridge is obtuse, and only separated from the little head, already described, by a small fossa, in which the joined edges of the ulna and radius move.—The internal protuberance of the pulley is largest and highest; and therefore, in the motions of the ulna upon it, that bone would be inclined outwards, was it not supported by the radius on that side.—Between this internal protuberance and condyle, a sinuosity may be remarked, where the ulnar nerve passes.

The round head at the upper end of this bone is articulated with the glenoid cavity of the scapula; which being superficial, and having long ligaments, allows the arm a free and extensive motion.

The motions which the arm enjoys by this articulation, are to every side; and by the succession of these different motions, a circle may be described. Besides which, the bone performs a small rotation round its own axis.

The FORE-ARM consists of two long bones, the ulna and radius; whose situation, in respect of each other, is oblique in the least straining or most natural posture; that is, the ulna is not directly behind, nor on the outside of the radius, but in a middle situation between these two, and the radius crosses it.—In the following description, by the term posterior is meant that part which is in the same direction with the back of the hand; by anterior, that answering to the palm; by internal, that on the same side with the thumb; by external, the side nearest the little finger.

ULNA, so named from its being used as a measure, is the longest of the two bones of the fore-arm, and situated on the outside of the radius.

At the upper end of the ulna are two processes.—The posterior is the largest, and formed like a hook, whose concave surface moves upon the pulley of the os humeri, and is called olecranon, or top of the cubitus.—The convex back-part of it is rough and scabrous, where the lon-

gus, brevis, and brachio-ulnaris externus, are inserted. The olecranon makes it unnecessary that the tendons of the extensor muscles should pass over the end of the os humeri; which would have been of ill consequence in the great flexions of this joint, or when any considerable external force is applied to this part.—The anterior process is not so large, nor does it reach so high as the one behind; but is sharper at its end, and therefore is named coronoid.—Between these two processes, a large semicircular or sigmoid concavity is left; the surface of which, on each side of a middle rising, is flanting, and exactly adapted to the pulley of the bone of the arm.—Across the middle of it, there is a small sinuosity for lodging mucilaginous glands; where, as well as in a small hollow on the internal side of it, the cartilage that lines the rest of its surface is wanting.—Round the brims of this concavity the bone is rough, where the capsular ligament of the joint is implanted.—Immediately below the olecranon, on the back-part of the ulna, a flat, triangular, spongy surface appears, on which we commonly lean.—At the internal side of this, there is a larger hollow surface, where the musculus anconeus is lodged; and the ridge at the inside of this gives rise to the musculus supinator radii brevis.—Between the top of the ridge and the coronoid process, is the semilunar smooth cavity, lined with cartilage, in which, and a ligament extended from the one to the other end of this cavity, the round head of the radius plays.—Immediately below it, a rough hollow gives lodging to mucilaginous glands.—Below the root of the coronoid process, this bone is scabrous and unequal, where the brachio-ulnaris internus is inserted.—On the outside of that, we observe a smooth concavity, where the beginning of the flexor digitorum profundus sprouts out.

The body of the ulna is triangular.—The internal angle is very sharp where the ligament that connects the two bones is fixed; the sides, which make this angle, are flat and rough, by the action and adhesion of the many muscles which are situated here.—At the distance of one third of the length of the ulna from the top, in its fore-part, the passage of the medullary vessels is to be remarked flanting upwards.—The external side of this bone is smooth, somewhat convex, and the angles at each edge of it are blunted by the pressure of the muscles equally disposed about them.

As this bone descends, it becomes gradually smaller; so that its lower end terminates in a little head, standing on a small neck.—Towards the fore but outer part of which last, an oblique ridge runs, that gives rise to the pronator radii quadratus.—The head is round, smooth, and covered with a cartilage on its internal side, to be received into the semilunar cavity of the radius; while a styloid process rises from its outside, to which is fixed a strong ligament that is extended to the os cuneiforme and pisiforme of the wrist.—Between the back-part of that internal smooth side and this process, a sinuosity is left for the tendon of the extensor carpi ulnaris.—On the fore-part of the root of the process, such another depression may be remarked for the passage of the ulnar artery and nerve.—The end of the bone is smooth, and covered with a cartilage.—Between it and the bones of the

the wrist, a double concave moveable cartilage is interposed; which is a continuation of the cartilage that covers the lower end of the radius, and is connected loosely to the root of the styloid process, and to the rough cavity there, in which mucilaginous glands are lodged.

The ulna is articulated above with the lower end of the os humeri, where these bones have depressions and protuberances corresponding to each other, so as to allow an easy and secure extension of the fore-arm to almost a straight line with the arm, and flexion to a very acute angle; but, by the slanting position of the pulley, the lower part of the fore-arm is turned outwards in the extension, and inwards in the flexion; and a very small kind of rotation is likewise allowed in all positions, especially when the ligaments are most relaxed by the fore-arm being in a middle degree of flexion.—The ulna is also articulated with the radius and carpus, in a manner to be related afterwards.

RADIUS, so called from its imagined resemblance to a spoke of a wheel, is the bone placed at the inside of the fore-arm. Its upper end is formed into a circular little head, which is hollowed for an articulation with the tubercle at the side of the pulley of the os humeri; and the half of the round circumference of the head next to the ulna is smooth, and covered with a cartilage, in order to be received into the semilunated cavity of that bone.—Below the head, the radius is much smaller; therefore this part is named its cervix, which is made round by the action of the supinator radii brevis.—At the external root of this neck, a tubercle rises; into the outer part of which the biceps flexor cubiti is inserted.—From this a ridge runs downwards and inwards, where the supinator radii brevis is inserted; and a little below, and behind this ridge, there is a rough scabrous surface, where the pronator radii teres is fixed.

The body of the radius is not straight, but convex on its internal and posterior surfaces; where it is also made round by the equal pressure of the circumjacent muscles, particularly of the extensors of the thumb; but the surfaces next to the ulna are flattened and rough, for the origin of the muscles of the hand; and both terminate in a common sharp spine, to which the strong ligament extended betwixt the two bones of the fore-arm is fixed. A little below the beginning of the plain surface, on its fore-part, where the flexor muscle of the last joint of the thumb takes its origin, the passage of the medullary vessels is seen flanting upwards.—The radius becomes broader and flatter towards the lower end, especially on its fore-part, where its pronator quadratus muscle is situated.

The lower end of the radius is larger than the superior; though not in such a disproportion as the upper end of the ulna is larger than its lower end.—Its back-part has a flat strong ridge in the middle, and fossæ on each side.—In a small groove immediately on the outside of the ridge, the tendon of the extensor tertii internodii pollicis plays.—In a large one beyond this, the tendons of the indicator and of the common extensor muscles of the fingers pass.—Contiguous to the ulna, there is a small depression made by the extensor minimi digiti.

—On the outside of the ridge there is a broad depression, which seems again subdivided, where the two tendons of the bicornis, or extensor carpi radialis, are lodged.—The internal side of this end of the radius is also hollowed by the extensors of the first and second joint of the thumb; immediately above which, a little rough surface shews where the supinator radii longus is inserted.—The ridges at the sides of the grooves, in which the tendons play, have an annular ligament fixed to them, by which the several sheaths for the tendons are formed.—The fore-part of this end of the radius is also depressed, where the flexors of the fingers and flexor carpi radialis pass.—The external side is formed into a semilunated smooth cavity, lined with a cartilage, for receiving the lower end of the ulna.—The lowest part of the radius is formed into an oblong cavity; in the middle of which is a small transverse rising, gently hollowed, for lodging mucilaginous glands; while the rising itself is insinuated into the conjunction of the two bones of the wrist that are received into the cavity.—The internal side of this articulation is fenced by a remarkable process of the radius, from which a ligament goes out to the wrist, as the styloid process of the ulna with its ligament guards it on the outside.

The ends of both the bones of the fore-arm being thicker than the middle, there is a considerable distance between the bodies of these bones; in the larger part of which a strong tendinous, but thin ligament, is extended, to give a large enough surface for the origin of the numerous fibres of the muscles situated here, that are so much sunk between the bones, as to be protected from injuries, which they would otherwise be exposed to.

As the head of the radius receives the tubercle of the os humeri, it is not only bent and extended along with the ulna, but may be moved round its axis in any position; and that this motion round its axis may be sufficiently large, the ligament of the articulation is extended farther down than ordinary on the neck of this bone, before it is connected to it; and it is very thin at its upper and lower part, but makes a firm ring in the middle.—This bone is also joined to the ulna by a double articulation; for above, a tubercle of the radius plays in a socket of the ulna; whilst below, the radius gives the socket, and the ulna the tubercle: But then the motion performed in these two is very different; for, at the upper end, the radius does no more than turn round its axis; while, at the lower end, it moves in a sort of cycloid upon the round part of the ulna; and as the hand is articulated and firmly connected here with the radius, they must move together.—When the palm is turned uppermost, the radius is said to perform the supination; when the back of the hand is above, it is said to be prone.

The HAND comprehends all from the joint of the wrist to the points of the fingers. Its back-part is convex, for greater firmness and strength; and it is concave before, for containing more surely and conveniently such bodies as we take hold of.

The hand is commonly divided into the carpus, metacarpus, and fingers.

The CARPUS is composed of eight small spongy bones, situated at the upper part of the hand, viz. the

os scaphoides, lunare, cuneiforme, pisiforme, trapezium, trapezoides, magnum, unciforme.

The scaphoides is situated most internally of those that are articulated with the fore-arm.—The lunare is immediately on the outside of the former.—The cuneiforme is placed still more externally, but does not reach so high up as the other two.—The pisiforme stands forwards into the palm from the cuneiforme.—The trapezium is the first of the second row, and is situated betwixt the scaphoides and first joint of the thumb.—The trapezoides is immediately on the outside of the trapezium.—The os magnum is still more external.—The unciforme is farther to the side of the little finger.

Os scaphoides is the largest of the eight except one. It is convex above, concave and oblong below; from which small resemblance of a boat it has got its name.—Its smooth convex surface is divided by a rough middle fossa, which runs obliquely cross it.—The upper largest division is articulated with the radius.—Into the fossa the common ligament of the joint of the wrist is fixed; and the lower division is joined to the trapezium and trapezoides.—The concavity receives more than an half of the round head of the os magnum.—The external side of this hollow is formed into a semilunar plane, to be articulated with the following bone.—The internal, posterior, and anterior edges are rough, for fixing the ligaments that connect it to the surrounding bones.

Os lunare has a smooth convex upper surface, by which it is articulated with the radius.—The internal side, which gives the name to the bone, is in the form of a crescent, and is joined with the scaphoid;—the lower surface is hollow, for receiving part of the head of the os magnum.—On the outside of this cavity is another smooth, but narrow oblong sinuosity, for receiving the upper end of the os unciforme:—On the outside of which a small round convexity is found, for its connection with the os cuneiforme. Between the great convexity above, and the first deep inferior cavity, there is a rough fossa, in which the circular ligament of the joint of the wrist is fixed.

Os cuneiforme is broader above, and towards the back of the hand, than it is below and forwards: which gives it the resemblance of a wedge.—The superior slightly convex surface is included in the joint of the wrist, being opposed to the lower end of the ulna.—Below this, the cuneiform bone has a rough fossa, wherein the ligament of the articulation of the wrist is fixed.—On the internal side of this bone, where it is contiguous to the os lunare, it is smooth and slightly concave.—Its lower surface, where it is contiguous to the os unciforme, is oblong, somewhat spiral, and concave.—Near the middle of its anterior surface, a circular plane appears, where the os pisiforme is sustained.

Os pisiforme is almost spherical, except one circular plane, or slightly hollow surface, which is covered with cartilage for its motion on the cuneiform bone, from which its whole rough body is prominent forwards into the palm; having the tendon of the flexor carpi ulnaris, and a ligament from the styloid process of the ulna, fixed to its upper part; the transverse ligament of the wrist is connected to its internal side; ligaments extended to the

unciform bone, and to the os metacarpal of the little finger, are attached to its lower part; the abductor minimi digiti has its origin from its fore-part; and, at the internal side of it, a small depression is formed, for the passage of the ulnar nerve.

Trapezium has four unequal sides and angles in its back-part, from which it has got its name.—Above, its surface is smooth, slightly hollowed, and semicircular, for its conjunction with the os scaphoides.—Its external side is an oblong concave square, for receiving the following bone.—The inferior surface is formed into a pulley; the two protuberant sides of which are external and internal. On this pulley the first bone of the thumb is moved.—At the external side of the external protuberance, a small oblong smooth surface is formed by the os metacarpal indicis.—The fore-part of the trapezium is prominent in the palm, and, near to the external side, has a sinuosity in it, where the tendon of the flexor carpi radialis is lodged; on the ligamentous sheath of which the tendon of the flexor tertii internodii pollicis plays: And still more externally the bone is scabrous, where the transverse ligament of the wrist is connected, the abductor and flexor primi internodii pollicis have their origin, and ligaments go out to the first bone of the thumb.

Os trapezoides, so called from the irregular quadrangular figure of its back-part, is the smallest bone of the wrist, except the pisiforme.—The figure of it is an irregular cube.—It has a small hollow surface above, by which it joins the scaphoides; a long convex one internally, where it is contiguous to the trapezium; a small external one, for its conjunction with the os magnum; and an inferior convex surface, the edges of which are however so raised before and behind, that a sort of pulley is formed, where it sustains the os metacarpal indicis.

Os magnum, so called because it is the largest bone of the carpus, is oblong, having four quadrangular sides, with a round upper end, and a triangular plain one below.—The round head is divided by a small rising, opposite to the connection of the os scaphoides and lunare, which together form the cavity for receiving it.—On the inside, a short plain surface joins the os magnum to the trapezoides.—On the outside is a long narrow concave surface, where it is contiguous to the os unciforme.—The lower end, which sustains the metacarpal bone of the middle finger, is triangular, slightly hollowed, and farther advanced on the internal side than on the external, having a considerable oblong depression made on the advanced inside by the metacarpal bone of the fore-finger; and generally there is a small mark of the os metacarpal digiti annularis on its external side.

Os unciforme has got its name from a thin broad process that stands out from it forwards into the palm, and is hollow on its inside, for affording passage to the tendons of the flexors of the fingers. To this process also the transverse ligament is fixed, that binds down and defends these tendons; and the flexor and abductor muscles of the little finger have part of their origin from it.—The upper plain surface is small, convex, and joined with the os lunare:—The internal side is long, and slightly convex, adapted to the contiguous os magnum:—The

The external surface is oblique, and irregularly convex, to be articulated with the cuneiform bone:—The lower end is divided into two concave surfaces; the external is joined with the metacarpal bone of the little finger, and the internal one is fitted to the metacarpal bone of the ring-finger.

The uses of the carpus are, to serve as a base to the hand, to protect its tendons, and to afford it a free large motion.

METACARPUS consists of four bones, which sustain the fingers.—Each bone is long and round, with its ends larger than its body.—The upper end, which some call the base, is flat and oblong, without any considerable head or cavity; but it is however somewhat hollowed, for the articulation with the carpus: It is made flat and smooth on the sides where these bones are contiguous to each other.—Their bodies are flattened on their back-part by the tendons of the extensors of the fingers.—The anterior surface of these bodies is a little concave, especially in their middle; along which a sharp ridge stands out, which separates the musculi interossii placed on each side of these bones, which are there made flat and plain by these muscles.

Their lower ends are raised into large oblong smooth heads, whose greatest extent is forwards from the axis of the bone.—At the fore-part of each side of the root of each of these heads, one or two tubercles stand out, for fixing the ligaments that go from one metacarpal bone to another, to preserve them from being drawn asunder:—Round the heads a rough ring may be remarked, for the capsular ligaments of the first joints of the fingers to be fixed to; and both sides of these heads are flat, by pressing on each other.

The concavity on the fore-part of these metacarpal bones, and the placing their basis on the arched carpus, cause them to form a hollow in the palm of the hand, which is useful often to us.—The spaces between them lodge muscles, and their small motion makes them fit supporters for the fingers to play on.

Though the ossa metacarpi so far agree, yet they may be distinguished from each other by the following marks.

The os metacarpi indicis is generally the longest.—Its base, which is articulated with the os trapezoides, is hollow in the middle.—The small ridge on the internal side of this oblong cavity is smaller than the one opposite to it, and is made flat on the side by the trapezium.—The exterior ridge is also smooth, and flat on its outside, for its conjunction with the os magnum; immediately below which, a semicircular smooth flat surface shows the articulation of this to the second metacarpal bone.—The back-part of this base is flattened, where the long head of the extensor carpi radialis is inserted; and its fore-part is prominent, where the tendon of the flexor carpi radialis is fixed.—The external side of the body of this bone is more hollowed by the action of muscles, than the internal.—The tubercle at the internal root of its head is larger than the external.—Its base is so firmly fixed to the bone it is connected with, that it has no motion.

Os metacarpi medii digiti is generally the second in length.—Its base is a broad superficial cavity, flating

outwards; the internal posterior angle of which is so prominent, as to have the appearance of a process.—The internal side of this base is made plain in the same way as the external side of the former bone, while its external side has two hollow circular surfaces, for joining the third metacarpal bone; and between these surfaces there is a rough fossa, for the adhesion of a ligament, and lodging mucilaginous glands.—The shorter head of the bicornis is inserted into the back-part of this base.—The two sides of this bone are almost equally flattened; only the ridge on the fore-part of the body inclines outwards.—The tubercles at the fore-part of the root of the head are equal.—The motion of this bone is very little more than the first metacarpal one has; and therefore these two firmly resist bodies pressed against them by the thumb, or fingers, or both.

Os metacarpi digiti annularis is shorter than the second metacarpal bone.—Its base is semicircular and convex, for its conjunction with the os unciniforme.—On its internal side are two smooth convexities, and a middle fossa, adapted to the second metacarpal bone.—The external side has a triangular smooth concave surface to join it with the fourth one. The anterior ridge of its body is situated more to the out than to the in-side.—The tubercles near the head are equal.—The motion of this third metacarpal bone is greater than the motion of the second.

Os metacarpi minimi digiti is the smallest and sharpest.—Its base is irregularly convex, and rises slanting outwards.—Its internal side is exactly adapted to the third metacarpal bone.—The external has no smooth surface, because it is not contiguous to any other bone; but it is prominent where the extensor carpi ulnaris is inserted.—As this metacarpal bone is furnished with a proper moving muscle, has the plainest articulation, is most loosely connected and least confined, it not only enjoys a much larger motion than any of the rest, but draws the third bone with it, when the palm of the hand is to be made hollow by its advancement forwards, and by the prominence of the thumb opposite to it.

The THUMB and four FINGERS are each composed of three long bones.

The thumb is situated obliquely in respect of the fingers, neither opposite directly to them, nor in the same plane with them.—All its bones are much thicker and stronger in proportion to their length, than the bones of the fingers are: Which was extremely necessary, since the thumb counteracts all the fingers.

The first bone of the thumb has its base adapted to the double pulley of the trapezium.—The edge at the fore-part of this base is produced farther than any other part; and round the back-part of the base a rough fossa may be seen, for the connection of the ligaments of this joint.—The body and head of this bone are of the same shape as the ossa metacarpi: only that the body is shorter, and the head flatter, with the tubercles at the fore-part of its root larger.

The articulation of the upper end of this bone is uncommon: For though it has protuberances and depressions adapted to the double pulley of the trapezium; yet it enjoys a circular motion, as the joints do where a

round head of one bone plays in the orbicular socket of another; only it is somewhat more confined and less expeditious, but stronger and more secure, than such joints generally are.

The second bone of the thumb has a large base formed into an oblong cavity, whose greatest length is from one side to the other.—Round it several tubercles may be remarked, for the insertion of ligaments.—Its body is convex, or a half-round behind; but flat before, for lodging the tendon of the long flexor of the thumb, which is tied down by ligamentous sheaths that are fixed on each side to the angle at the edge of this flat surface.

The articulation and motion of the upper end of this second bone is as singular as that of the former.—For its cavity being joined to the round head of the first bone, it would seem at first view to enjoy motion in all directions; yet, because of the strength of its lateral ligaments, oblong figure of the joint itself, and mobility of the first joint, it only allows flexion and extension; and these are generally much confined.

The third bone of the thumb is the smallest, with a large base, whose greatest extent is from one side to the other.—This base is formed into two cavities and a middle protuberance, to be adapted to the pulley of the former bone.—Its body is rounded behind; but is flatter than in the former bone, for sustaining the nail.—It is flat and rough before, by the insertion of the flexor tertii internodii.—This bone becomes gradually smaller, till near the lower end, where it is a little enlarged, and has an oval scabrous edge.

The motion of this third bone is confined to flexion and extension.

The orderly disposition of the bones of the fingers into three rows, has made them generally obtain the name of three phalanges.—All of them have half-round convex surfaces, covered with an aponeurosis, formed by the tendons of the extensors, lumbricales, and interossei, and placed directly backwards, for their greater strength; and their flat concave part is forwards, for taking hold more surely, and for lodging the tendons of the flexor muscles.—The ligaments for keeping down these tendons are fixed to the angles that are between the convex and concave sides.

The bones of the first phalanx of the fingers answer to the description of the second bone of the thumb: only that the cavity in their base is not so oblong; nor is their motion on the metacarpal bones so much confined; for they can be moved laterally or circularly, but have no rotation, or a very small degree of it, round their axis.

The second bone of the fingers has its base formed into two lateral cavities, and a middle protuberance; while the lower end has two lateral protuberances, and a middle cavity; therefore it is joined at both ends in the same manner, which none of the bones of the thumb are.

The third bone differs nothing from the description of the third bone of the thumb, excepting in the general distinguishing marks; and therefore the second and third phalanges of the fingers enjoy only flexion and extension.

All the difference of the phalanges of the several fingers consists in their magnitude.—The bones of the

middle-finger being the longest and largest.—Those of the fore-finger come next to that in thickness, but not in length, for those of the ring-finger are a little longer. The little finger has the smallest bones. Which disposition is the best contrivance for holding the largest bodies; because the longest fingers are applied to the middle largest periphery of such substances as are of a spherical figure.

The uses of all the parts of our superior extremities are so evident in the common actions of life, that it is needless to enumerate them here; and therefore we shall proceed to the last part of the skeleton.

OF THE INFERIOR EXTREMITIES.

THE INFERIOR EXTREMITIES depend from the acetabula of the ossa innominata; are commonly divided into three parts, viz. the thigh, leg, and foot.

THE THIGH has only one bone; which is the longest of the body. The situation of it is not perpendicular; for the lower end is inclined considerably inwards: So that the knees are almost contiguous, while there is a considerable distance between the thigh-bones above: Which is of good use to us, since sufficient space is thereby left for the external parts of generation, the two great cloaces of urine and feces, and for the large thick muscles that move the thigh inwards: And, at the same time, this situation of the thigh-bones renders our progression quicker, surer, straighter, and in less room.

The upper end of the thigh-bone is not continued in a straight line with the body of it, but is set off obliquely inwards and upwards, whereby the distance here between these two bones at their upper part is considerably increased.—This end is formed into a large smooth round head, which is the greater portion of a sphere-unequally divided.—Towards its lower internal part, a round rough spongy pit is observable, where the strong ligament, commonly called the round one, is fixed, to be extended from thence to the lower internal part of the receiving cavity, where it is considerably broader than near to the head of the thigh-bone.—The small part below the head, called the cervix, of the os femoris, has a great many large holes, into which the fibres of the strong ligament, continued from the capsular, enter, and are thereby surely united to it; and round the root of the neck, where it rises from the bone, a rough ridge is found, where the capsular ligament of the articulation itself is connected.—Below the back-part of this root, the large unequal protuberance, called trochanter major, stands out; the external convex part of which is distinguished into three different surfaces, whereof the one on the fore-part is scabrous and rough, for the insertion of the gluteus minimus; the superior one is smooth, and has the gluteus medius inserted into it; and the one behind is made flat and smooth by the tendon of the gluteus maximus passing over it.—The upper edge of this process is sharp and pointed at its back-part, where the gluteus medius is fixed; but forwards it is more obtuse, and has two superficial pits formed in it: Into the superior of these, the piriformis is implanted; and the obturator internus and gemini are fixed into the lower one.

one.—From the backmost prominent part of this great trochanter, a rough ridge runs backwards and downwards, into which the quadratus is inserted.—In the deep hollow, at the internal upper side of this ridge, the obturator externus is implanted.—More internally, a conoid process, called trochanter minor, rises, for the insertion of the musculus psoas and iliacus internus, and the pectineus is implanted into a rough hollow below its internal root.—The muscles inserted into these two processes being the principal instruments of the rotatory motion of the thigh, have occasioned the name of trochanters to the processes.

The body of the os femoris is convex on the fore-part, and made hollow behind, by the action of the muscles that move it and the leg, and for the convenience of fitting, without bearing too much on these muscles.—The fore-part of the thigh-bone is a little flattened above by the beginning of the crureus muscle, as it is also below by the same muscle and the rectus.—Its external surface is likewise made flat below by the vastus externus, where it is separated from the former by an obtuse ridge.—The vastus internus depresses a little the lower part of the internal surface.—The posterior concave surface has a ridge rising in its middle, commonly called linea aspera, into which the triceps is inserted, and the short head of the biceps flexor tibiae rises from it.—At the upper part of it, the medullary vessels enter by a small hole that runs obliquely upwards.—A little above which, there is a rough fossa or two, where the tendon of the gluteus maximus is fixed.—The lower end of the linea aspera divides into two, which descend towards each side.—The two vasti muscles have part of their origin from these ridges; and the long tendon of the triceps is fixed to the internal, by means of part of the fascia aponeurotica of the thigh.—Near the beginning of the internal ridge, there is a discontinuation of the ridge, where the crural artery passes through the aponeurosis.—Between these two rough lines, the bone is made flat by the large blood-vessels and nerves which pass upon it; and near the end of each of these ridges, a small smooth protuberance may often be remarked, where the two heads of the external gastrocnemius muscle take their rise; and from the fore-part of the internal tubercle, a strong ligament is extended to the inside of the tibia.

The lower end of the os femoris is larger than any other part of it, and is formed into a great protuberance on each side, called its condyles; between which a considerable cavity is found, especially at the back-part, in which the crural vessels and nerves lie immersed in fat.—The internal condyle is longer than the external.—Each of these processes seems to be divided in its plain smooth surface. The mark of division on the external is a notch, and on the internal a small protuberance. The fore-part of this division, on which the rotula moves, is formed like a pulley, the external side of which is highest.—Behind, there are two oblong large heads, whose greatest extent is backwards, for the motion of the tibia; and from the rough cavity between them, but near to the base of the internal condyle, the strong ligament, commonly called the cross one, has its rise.—A little

above which, a rough protuberance gives insertion to the tendon of the triceps.—The condyles, both on the outer and inner side of the knee, are made flat by the muscles passing along them.—On the back part of the internal, a slight depression is made by the tendons of the gracilis and fartorius; and on the external, such another is formed by the biceps flexor cruris; behind which, a deep fossa is to be observed, where the popliteus muscle has its origin.—From the tubercle immediately before this cavity, a strong round ligament goes out to the upper part of the fibula.—Round this lower end of the thigh-bone, large holes are found, into which the ligaments for the security of the joint are fixed, and blood-vessels pass to the internal substance of the bone.

The thigh-bone being articulated above with the acetabulum of the ossa innominata, which affords its round head a secure and extensive play, can be moved to every side; but is restrained in its motion outwards by the high brims of the cavity, and by the round ligament; for otherwise the head of the bone would have been frequently thrust out at the breach of the brims on the inside, which allows the thigh to move considerably inwards.—The body of this bone enjoys little or no rotatory motion, though the head most commonly moves round its own axis; because the oblique progress of the neck and head from the bone is such, that the rotatory motion of the head can only bring the body of the bone forwards and backwards.—The os femoris is articulated below to the tibia and rotula in the manner afterwards to be described.

The nearness of the small neck to the round head of the thigh-bone, and its upper end being covered with very thick muscles, make greater difficulty in distinguishing between a luxation and fracture here, than in any other part of the body.

The LEG is composed of three bones, tibia, fibula, and rotula.

TIBIA, so called from its resemblance to an old musical pipe or flute, is the long, thick, triangular bone, situated at the internal part of the leg, and continued in almost a straight line from the thigh-bone.

The upper end of the tibia is large, bulbous, and spongy, and is divided into two cavities by a rough irregular protuberance, which is hollow at its most prominent part, as well as before and behind. The anterior of the two ligaments that compose the great cross one, is inserted into the middle cavity, and the depression behind receives the posterior ligament.—The two broad cavities at the sides of this protuberance are not equal; for the internal is oblong and deep, to receive the internal condyle of the thigh-bone; while the external is more superficial and rounder, for the external condyle.—In each of these two cavities of a recent subject, a femoral cartilage is placed, which is thick at its convex edge, and becomes gradually thinner towards the concave or interior edge.—The middle of each of these cartilages is broad, and the ends of them turn narrower and thinner, as they approach the middle protuberance of the tibia.—The thick convex edge of each cartilage is connected to the capsular and other ligaments of the articulation, but so near to their rise from the tibia, that the cartilages

cartilages are not allowed to change place far; while the narrow ends of the cartilages, becoming almost ligaments, are fixed at the insertion of the strong cross ligament into the tibia, and seem to have their substance united with it; therefore a circular hole is left between each cartilage and the ligament, in which the most prominent convex part of each condyle of the thigh-bone moves.—The circumference of these cavities is rough and unequal, for the firm connection of the ligaments of the joint.—Immediately below the edge, at its back-part, two rough flattened protuberances stand out: Into the internal, the tendon of the femimembranosus muscle is inserted; and a part of the cross ligament is fixed to the external.—On the outside of this last tubercle, a smooth slightly-hollowed surface is formed by the action of the popliteus muscle.

Below the fore-part of the upper end of the tibia, a considerable rough protuberance rises, to which the strong tendinous ligament of the rotula is fixed.—On the internal side of this, there is a broad, scabrous, slightly-hollowed surface, to which the internal long ligament of the joint, the aponeurosis of the vastus internus, and the tendons of the feminervosus, gracilis, and sartorius, are fixed.—Below the external edge of the upper end of the tibia, there is a circular flat surface, covered, in a recent subject, with cartilage, for the articulation of the fibula;—between which and the anterior knob, there is a rough hollow, from which the tibialis anticus, and extensor digitorum longus, take their origin.—From the smooth flat surface, a ridge runs obliquely downwards and inwards, to give rise to part of the soleus, tibialis posticus, and flexor digitorum longus, and insertion to the aponeurosis of the femimembranosus which covers the popliteus, and to some of the external fibres of this last named muscle.—At the inside of this ridge an oblique plain surface is left, where the greatest part of the musculus popliteus is inserted.—The remaining body of the tibia is triangular.—The anterior angle is very sharp, and is commonly called the spine or shin. This ridge is not straight; but turns first inwards, then outwards, and lastly inwards again.—The plain internal side is smooth and equal, being little subjected to the actions of muscles; but the external side is hollowed above by the tibialis anticus, and below by the extensor digitorum longus, and extensor pollicis longus.—The two angles behind these sides are rounded by the action of the muscles;—the posterior side comprehended between them is not so broad as those already mentioned, but is more oblique and flattened by the action of the tibialis posticus and flexor digitorum longus.—Some way above the middle of the bone, the internal angle terminates, and the bone is made round by the pressure of the musculus soleus.—Near to this, the passage of the medullary vessels is seen flanting obliquely downwards.

The lower end of the tibia is made hollow, but so as a small protuberance rises in the middle.—The internal side of this cavity, which is smooth, and, in a recent subject, is covered with cartilage, is produced into a considerable process, commonly named malleolus internus; the point of which is divided by a notch, and from it ligaments are sent out to the foot.—The external side

of this end of the tibia has a rough irregular femilunar cavity formed in it, for receiving the lower end of the fibula.—The posterior side has two lateral grooves, and a small middle protuberance. In the internal depression, the tendons of the musculus tibialis posticus, and flexor digitorum longus, are lodged; and in the external, the tendon of the flexor longus pollicis plays.—From the middle protuberance, ligamentous sheaths go out, for tying down these tendons.

FIBULA is the small long bone, placed on the outside of the leg, opposite to the external angle of the tibia; the shape of it is irregularly triangular.

The head of the fibula has a superficial circular cavity formed on its inside, which, in a recent subject, is covered with a cartilage, but so closely connected to the tibia by ligaments, as to allow only a small motion backwards and forwards.—This head is protuberant and rough on its outside, where a strong round ligament, and the musculus biceps, are inserted; and, below the back-part of its internal side, a tubercle may be remarked, that gives rise to the strong tendinous part of the soleus muscle.

The body of this bone is a little crooked inwards and backwards, which figure is owing to the actions of the muscles; but is still further increased by nurses, who often hold children carelessly by the legs.—The sharpest angle of the fibula is forwards, on each side of which the bone is considerably, but unequally, depressed by the bellies of the several muscles that rise from, or act upon it; and, in old people, these muscles make distinct sinuities for themselves.—The external surface of the fibula is depressed obliquely from above downwards and backwards, by the two peronæi.—Its internal surface is unequally divided into two narrow longitudinal planes, by an oblique ridge extended from the upper part of the anterior angle, to join with the lower end of the internal angle. To this ridge the ligament stretched between the two bones of the leg is connected.—The anterior of the two planes is very narrow above, where the extensor longus digitorum, and extensor longus pollicis, arise from it; but is broader below, where it has the print of the nonus Vesalii.—The posterior plane is broad and hollow, giving origin to the larger share of the tibialis posticus.—The internal angle of this bone has a tendinous membrane fixed to it, from which fibres of the flexor digitorum longus take their rise.—The posterior surface of the fibula is the plainest and smoothest, but is made flat above by the soleus, and is hollowed below by the flexor pollicis longus.—In the middle of this surface the canal for the medullary vessels may be seen flanting downwards.

The lower end of the fibula is extended into a spongy oblong head, on the inside of which is a convex, irregular, and frequently a scabrous surface, that is received by the external hollow of the tibia, and so firmly joined to it by a very thin intermediate cartilage and strong ligaments, that it scarce can move.—Below this, the fibula is stretched out into a coronoid process, that is smooth, covered with cartilage on its internal side, and is there contiguous to the outside of the first bone of the foot, the astragalus, to secure the articulation. This process, named malleolus externus, being situated farther back

back than the internal malleolus, and in an oblique direction, obliges us naturally to turn the fore-part of the foot outwards. At the lower internal part of this process, a spongy cavity for mucilaginous glands may be remarked; from its point, ligaments are extended to the astragalus, os calcis, and os naviculare, bones of the foot; and from its inside, short strong ones go out to the astragalus. On the back-part of it, a sinuosity is made by the tendons of the peronæi muscles.—When the ligament extended over these tendons from the one side of the depression to the other is broke, stretched too much, or made weak by a sprain, the tendons frequently start forwards to the outside of the fibula.

The conjunction of the upper end of the fibula with the tibia is, by plain surfaces, tipped with cartilage; and, at its lower end, the cartilage seems to glue the two bones together, not, however, so firmly in young people, but that the motion at the other end of such a long radius is very observable.

The principal use of this bone is to afford origin and insertion to muscles; the direction of which may be a little altered, on proper occasions, by its upper part shuffling backwards and forwards.—It likewise helps to make the articulation of the foot more secure and firm.

ROTULA is the small flat bone situated at the fore-part of the joint of the knee.—Its shape resembles the common figure of the heart with its point downwards.—The anterior convex surface of the rotula is pierced by a great number of holes, into which fibres of the strong ligament that is spread over it enter.—Behind, its surface is smooth, covered with cartilage, and divided by a middle convex ridge into two cavities, of which the external is largest, and both are exactly adapted to the pulley of the os femoris, on which they are placed in the most ordinary unstraining postures of the leg; but when the leg is much bended, the rotula descends far down on the condyles; and when the leg is fully extended, the rotula rises higher, in its upper part, than the pulley of the thigh-bone.—The plain smooth surface is surrounded by a rough prominent edge, to which the capsular ligament adheres:—Below, the point of the bone is scabrous, where the strong tendinous ligament from the tubercle of the tibia is fixed.—The upper horizontal part of this bone is flattened and unequal, where the tendons of the extensors of the leg are inserted.

The substance of the rotula is cellular, with very thin external firm plates: But then these cells are so small, and such a quantity of bone is employed in their formation, that scarce any bone of its bulk is so strong. Besides, it is covered all over with a thick ligament, to connect its substance, and is moveable to one side or other; therefore is sufficiently strong to resist the ordinary actions of the large muscles that are inserted into it, or any common external force applied to it.

The parts which constitute the joint of the knee being now described, let us examine what are its motions, and how performed.—The two principal motions are flexion and extension.—In the former of these, the leg may be brought to a very acute angle with the thigh, by the condyles of the thigh-bone being round and made

smooth far backwards. In performing this, the rotula is pulled down by the tibia.—When the leg is to be extended, the rotula is drawn upwards, consequently the tibia forwards, by the extensor muscles; which, by means of the protuberant joint, and of this thick bone with its ligament, have in effect the chord, with which they act, fixed to the tibia at a considerable angle, therefore act with advantage; but are restrained from pulling the leg farther than to a straight line with the thigh, by the posterior part of the cross ligament, that the body might be supported by a firm perpendicular column: For at this time the thigh and leg are as little moveable in a rotatory way, or to either side, as if they were one continued bone.—But when the joint is a little bended, the rotula is not tightly braced, and the posterior ligament is relaxed; therefore this bone may be moved a little to either side, or with a small rotation in the superficial cavities of the tibia; which is done by the motion of the external cavity backwards and forwards, the internal serving as a sort of axis. Seeing then one part of the cross ligament is situated perpendicularly, and the posterior part is stretched obliquely from the internal condyle of the thigh outwards, that posterior part of the cross ligament prevents the leg's being turned at all inwards; but it could not hinder it from turning outwards almost round, was not that motion confined by the lateral ligaments of this joint, which can yield little.

The foot is divided into three parts, viz. tarsus, metatarsus, and toes: In the description of which, the broad of the foot shall be called superior; the sole, inferior; the side on which the great toe is, internal; that where the little toe is, external.

The tarsus consists of seven spongy bones; to wit, the astragalus, os calcis, naviculare, cuboides, cuneiforme externum, cuneiforme medium, and cuneiforme internum.

The astragalus is the uppermost of these bones.—The os calcis is below the astragalus, and is considerably prominent backwards beyond the other bones, to form the heel.—The os naviculare is in the middle of the internal side of the tarsus.—The os cuboides is the most external of the row of four bones at its fore-part.

The os cuneiforme externum is placed at the inside of the cuboid.—The cuneiforme medium is between the external and internal cuneiform bones, and the internal cuneiform is put at the internal side of the foot.

In the description of these bones, let it be observed, That where-ever a ridge is mentioned, without a particular use assigned, a ligament is understood to be fixed to it: or where a spongy rough cavity, depression, or fossa, is remarked, without naming its use, a ligament is inserted, and mucilaginous glands are lodged.

The upper part of the astragalus is formed into a large smooth head, which is slightly hollowed in the middle; and therefore resembles a superficial pulley, by which it is fitted to the lower end of the tibia.—The internal side of this head is flat and smooth, to play on the internal malleolus.—The external side has also such a surface, but larger, for its articulation with the external malleolus.—Round the base of this head there is a rough fossa; and, immediately before the head, as also

below its internal smooth surface, we find a considerable rough cavity.

The lower surface of the astragalus is divided by an irregular, deep, rough fossa; which, at its internal end, is narrow, but gradually widens, as it stretches obliquely outwards and forwards.—The smooth surface, covered with cartilage, behind this fossa, is large, oblong, extended in the same oblique situation with the fossa, and concave, for its conjunction with the os calcis.—The back-part of the edge of this cavity is produced into two sharp-pointed rough processes, between which is a depression, made by the tendon of the flexor pollicis longus.—The lower surface before the fossa is convex, and composed of three distinct smooth planes. The long one behind, and the exterior or shortest, are articulated with the heel-bone; while the internal, which is the most convex of the three, rests and moves upon a cartilaginous ligament, that is continued from the calcaneum to the os scaphoides.

The fore-part of this bone is formed into a convex oblong smooth head, which is received by the os naviculare.—Round the root of this head, especially on the upper surface, a rough fossa may be remarked.

The astragalus is articulated above to the tibia and fibula, which together form one cavity. Though, in this articulation, the bones have prominences and cavities so small, as might allow motions in all directions; yet the flexion and extension are the most considerable, the other motions being confined by the maleoli, and by the strong ligaments which go out from the points of these processes to the astragalus and os calcis. The astragalus is joined below to the os calcis; and before, to the os naviculare, in the manner to be explained when these bones are described.

Calcaneum is the largest bone of the seven.—Behind, it is formed into a large knob, commonly called the heel: The surface of which is rough behind, where the tendon Achillis is inserted into it; and above, it is hollow and spongy. Farther forwards, on the upper surface of the calcaneum, there is an irregular, oblong, smooth convexity, adapted to the concavity at the back-part of the astragalus: And beyond this a narrow fossa is seen, which divides it from two small concave smooth surfaces, that are joined to the fore-part of the astragalus.—Behind the posterior of these smooth surfaces, which is the largest, a small sinuosity is made by the tendon of the flexor digitorum longus; at the fore-part of which a small rough protuberance appears, that gives rise to the musculus extensor digitorum brevis.

The external side of this bone is flat, with a superficial fossa running horizontally, in which the tendon of the musculus peroneus longus is lodged.—The internal side of the heel-bone is hollowed, for lodging the origin of the massa cornea Jac. Sylvii, and for the safe passage of tendons, nerves, and arteries.—Under the side of the internal smooth concavity, a particular groove is made by the tendon of the flexor pollicis longus; and from the thin protuberance on this internal side, the cartilaginous ligament that supports the astragalus, goes out to the os naviculare; on which ligament, and on the edge of this bone to which it is fixed, the groove is form-

ed for the tendon of the flexor digitorum profundus.

The lower surface of this bone is pressed flat at the back-part, by the weight of our bodies; and immediately before this plane, there are two tubercles, from the internal of which the musculus abductor pollicis, flexor digitorum sublimis, as also part of the aponeurosis plantaris, and of the abductor minimi digiti, have their origin; and the other part of the abductor minimi digiti and aponeurosis plantaris, rises from the external.—Before these protuberances this bone is concave, for lodging the flexor muscles; and at its fore-part we may observe a rough depression, from which, and a tubercle behind it, the ligament goes out that prevents this bone to be separated from the os cuboides.

The fore-part of the os calcis is formed into an oblong, pulley-like, smooth surface, which is circular at its upper external end, but is pointed below. This smooth surface is fitted to the os cuboides.

Though the surfaces by which the astragalus and os calcis are articulated, seem fit enough for motion; yet the very strong ligaments by which these bones are connected, prevent it, and render this principal part of our base, which rests on the ground, to wit, the os calcis, firm.

Os naviculare, is somewhat circular.—It is formed into an oblong concavity behind, for receiving the anterior head of the astragalus.—On the upper surface, there is a rough fossa.—Below, the os naviculare is very unequal and rough; but hollow for the safety of the muscles.—On its inside, a large knob rises out, from which the abductor pollicis takes in part its origin, the tendon of the tibialis posticus is inserted into it, and to it two remarkable ligaments are fixed; the first is the strong one, formerly mentioned, which supports the astragalus; the second is stretched from this bone obliquely across the foot, to the metatarsal bones of the middle toe, and of the toe next to the little one.—On the outside of the os naviculare, there is a semicircular smooth surface, where it is joined to the os cuboides.—The fore-part of this bone is all covered with cartilage, and is divided into three smooth planes, fitted to the three ossa cuneiformia.

The os naviculare and astragalus are joined as a ball and socket, and the naviculare moves in all directions in turning the toes inwards, or in raising or depressing either side of the foot, though the motions are greatly restrained by the ligaments which connect this to the other bones of the tarsus.

Os cuboides is a very irregular cube.—Behind, it is formed into an oblong unequal concavity, adapted to the fore-part of the os calcis.—On its internal side, there is a small semicircular smooth cavity, to join the os naviculare.—Immediately before which, an oblong smooth plane is made by the os cuneiforme externum.—Below this, the bone is hollow and rough.—On the internal side of the lower surface, a round protuberance and fossa are found, where the musculus adductor pollicis has its origin. On the external side of this same surface, there is a round knob, covered with cartilage; immediately before which, a smooth fossa may be observed, in which the tendon of the peroneus primus runs obliquely across the

the foot; and on the knob, the thin flat cartilage proper to this muscle plays; in place of which, sometimes a bone is found:—More externally than the knob, a rough hollow is made, for the strong ligaments stretched betwixt this bone and the os calcis.—Before, the surface of the os cuboides is flat, smooth, and slightly divided into two planes, for sustaining the os metatarsi of the little toe, and of the toe next to it.

The form of the back-part of the os cuboides, and the ligaments connecting the joint there with the os calcis, both concur in allowing little motion in this part.

Os cuneiforme externum, is much of the shape of a wedge, being broad and flat above, with long sides running obliquely downwards, and terminating in a sharp edge.—The upper surface of this bone is an oblong square.—The one behind is nearly a triangle, but not complete at the inferior angle, and is joined to the os naviculare.—The external side is an oblong square, divided as it were by a diagonal: The upper half of it is smooth, for its conjunction with the os cuboides: The other is a scabrous hollow; and in its superior anterior angle, a small smooth impression is made by the os metatarsi of the toe next to the little one.—The internal side of this bone is also quadrangular, with the fore-part of its edge made flat and smooth by the os metatarsi of the toe next to the great one; and the back-part is also flat and smooth, where the os cuneiforme medium is contiguous to it.—The fore-part of this bone is an oblong triangle, for sustaining the os metatarsi of the middle toe.

Os cuneiforme medium, or minimum, is still more exactly the shape of a wedge than the former.—Its upper part is square; its internal side has a flat smooth surface above and behind, for its conjunction with the following bone; with a small rough fossa below; and a considerable share of it is rough and hollow.—The external side is smooth and a little hollowed, where it is contiguous to the last described bone.—Behind, this bone is triangular, where it is articulated with the os naviculare; and it is also triangular at its fore-part, where it is contiguous to the os metatarsi of the toe next to the great one.

Os cuneiforme maximum, or internum, differs from the two former in its situation, which is more oblique than theirs.—Besides, its broad thick part is placed below, and the small thin point is above and outwards; while its under broad surface is concave, for allowing a safe passage to the flexors of the great toe.—The surface of this os cuneiforme behind, where it is joined to the os naviculare, is hollow, smooth, and of a circular figure below, but pointed above.—The external side consists of two smooth and flat-surfaces, whose direction is nearly at right angles with each other. With the posterior, that runs obliquely from below forwards and upwards, the os cuneiforme minimum is joined; and with the anterior, whose direction is longitudinal, the os metatarsi of the toe next to the great one is connected.—The fore-part of this bone is femicular, but flat and smooth, for sustaining the os metatarsi of the great toe.—The internal side is scabrous, with two remarkable tubercles below, from which the musculus abductor pollicis rises, and the tibialis anticus is inserted into its upper part.

The three cuneiform bones are all so secured by ligaments, that very little motion is allowed in any of them.

These seven bones of the tarsus, when joined, are convex above, and leave a concavity below, for lodging safely the several muscles, tendons, vessels, and nerves that lie in the sole of the foot.—In the recent subject, their upper and lower surfaces are covered with strong ligaments, which adhere firmly to them; and all the bones are so tightly connected, by these and the other ligaments, which are fixed to the rough ridges and fossa formerly mentioned, that, notwithstanding the many surfaces covered with cartilage, some of which are of the form of the very moveable articulations, no more motion is here allowed, than only to prevent too great a shock of the fabric of the body in walking, leaping, &c. by falling on too solid a base.

METATARSUS is composed of five bones, which, in their general characters, agree with the metacarpal bones; but may be distinguished from them by the following marks: 1. They are longer, thicker, and stronger. 2. Their anterior round ends are not so broad, and are less in proportion to their bases. 3. Their bodies are sharper above and flatter on the sides, with their inferior ridge inclined more to the outside. 4. The tubercles at the lower parts of the round head are larger.

The first or internal metatarsal bone is easily distinguished from the rest by its thickness.—The one next to it is the longest, and with its sharp edge almost perpendicular.—The others are shorter and more oblique, as their situation is more external.

Os metatarsi pollicis is by far the thickest and strongest, as having much the greatest weight to sustain. Its base is oblong, irregularly concave, and of a femicular figure, to be adapted to the os cuneiforme maximum.—The inferior edge of this base is a little prominent and rough, where the tendon of the peroneus primus muscle is inserted.—On its outside, an oblique circular depression is made by the second metatarsal bone.—Its round head has generally on its fore-part a middle ridge, and two oblong cavities, for the ossa sesamoidea; and on the external side, a depression is made by the following bone.

Os metatarsi of the second toe, is the longest of the five, with a triangular base supported by the os cuneiforme medium and the external side produced into a process; the end of which is an oblique smooth plane, joined to the os cuneiforme externum.—Near the internal edge of the base, this bone has two small depressions, made by the os cuneiforme maximum, between which is a rough cavity.—Farther forwards, we may observe a smooth protuberance, which is joined to the foregoing bone.—On the outside of the base are two oblong smooth surfaces, for its articulation with the following bone; the superior smooth surface being extended longitudinally, and the inferior perpendicularly; between which there is a rough fossa.

Os metatarsi of the middle toe, is the second in length.—Its base, supported by the os cuneiforme externum, is triangular, but flaring outwards, where it ends in a sharp-pointed little process; and the angle below is not completed.

The internal side of this base is adapted to the preceding bone; and the external side has also two smooth surfaces covered with cartilage, but of a different figure; for the upper one is concave, and, being round behind, turns smaller as it advances forwards; and the lower surface is little, smooth, convex, and very near the edge of the base.

Os metatarsi of the fourth toe, is near as long as the former, with a triangular flanting base, joined to the os cuboides, and made round at its external angle, having one hollow smooth surface on the outside, where it is pressed upon by the following bone, and two on the internal side, corresponding to the former bone; behind which is a long narrow surface impressed by the os cuneiforme externum.

Os metatarsi of the little toe, is the shortest, situated with its two flat sides above and below, and with the ridges laterally.—The base of it, part of which rests on the os cuboides, is very large, tuberous, and produced into a long-pointed process externally, where part of the abductor minimi digiti is fixed; and into its upper part the peroneus secundus is inserted.—Its inside has a flat conoidal surface, where it is contiguous to the preceding bone.

When we stand, the fore-ends of these metatarsal bones, and the os calcis, are our only supporters; and therefore it is necessary they should be strong, and should have a confined motion.

The bones of the Toes are much akin to those of the thumb and fingers; particularly the two of the great toe are precisely formed as the two last of the thumb; only their position, in respect of the other toes, is not oblique; and they are proportionally much stronger, because they are subjected to a greater force; for they sustain the force with which our bodies are pushed forwards by the foot behind at every step we make; and on them principally the weight of the body is supported, when we are raised on our tiptoes.

The three bones in each of the other four toes, compared to those of the fingers, differ from them in these particulars.—They are less, and smaller in proportion to their lengths:—Their bases are much larger than their anterior ends: Their bodies are more narrow above and below, and flatter on the sides.—The first phalanx

is proportionally much longer than the bones of the second and third, which are very short.

Of the four, the toe next to the great one has the largest bones in all dimensions, and more externally the toes are less.—The little toe, and frequently that next to it, have the second and third bones intimately united into one; which may be owing to their little motion, and the great pressure they are subjected to.

The toes are of good use to us in walking; for, when the sole is raised, they bring our body, with its centre of gravity, perpendicular to the advanced foot.

The only bones now remaining to complete the description of the skeleton, are the small ones, which are found at the joints of the fingers and toes, and in some other parts, called

Ossa SESAMOIDEA, which are of very different figures and sizes, though they are generally said to resemble the seed of the fescum.—They seem to be nothing else than the ligaments of the articulations, or the firm tendons of strong muscles, or both, become bony, by the compression which they suffer. Thus the sesamoid bones at the beginning of the gastrocnemii muscles, are evidently composed of the tendinous fibres only.—These, at the first joint of the great toe, are as plainly the same continued substance with the ligaments and the tendons of the adductor, flexor, brevis, and abductor.—That which is sometimes double at the second joint of that toe, is part of the capsular ligament; and if we enumerate the other sesamoid bones that are at any time found, we may observe all of them formed in this manner.—Their number, figure, situation, and magnitude, are so uncertain, that it were in vain to insist on the differences of each; and therefore we shall only in general remark,

1. That where-ever the tendons and ligaments are firmest, the actions of the muscles strongest, and the compression greatest, there such bones are most commonly found.

2. That, ceteris paribus, the older the subject is in which they are sought, their number is greater, and their size is larger.

3. The more labour any person is inured to, he has, ceteris paribus, the most numerous and largest ossa sesamoidea.

EXPLANATION OF PLATE XIII.

FIGURE I. A MALE SKELETON.

A, Os frontis. B, Os parietale. C, Os temporum. D, Os occipitis. E, Ossa nasi. F, Os malæ. G, Os maxillare superius. H, Os maxillare inferius. I, The teeth, which are sixteen in each jaw. K, The seven vertebrae of the neck, with their intermediate cartilages. L, &c. The twelve dorsal vertebrae, with their intermediate cartilages. M, The five lumbar vertebrae, and, N, Their intermediate cartilages. O, Os

facrum. P, Os coccygis. Q, Os ilium. R, Os pubis. S, Os ischium. T, The seven true ribs. U, The five false ribs. V, The sternum. X, The clavicle. Y, The scapula. Z, The os humeri. a, Ulna. b, Radius. c, The eight bones of the carpus. d, The five metacarpal bones. e, The phalanges of the fingers. f, The os femoris. g, The patella. h, The tibia. i, The fibula. k, The seven bones of the tarsus. l, The five metatarsal bones. m, The phalanges of the toes.

FIG.

a, The superior serrated edge, which assists to form the coronal future. b, The external angular process. c, The internal angular process. d, The nasal process. e, The orbital process. f, The frontal sinus. g, The sagittal future, which (as here) is sometimes continued to the nose.

a, Its superior edge, which, joined with the other, forms the sagittal future. b, The anterior edge, which assists in the formation of the coronal future. c, The inferior edge for the squamous future. d, The posterior edge for the lambdoid future. e, A depression made by the lateral sinus. f, The prints of the principal artery of the dura mater.

a a, The two sides, which assist to form the lambdoid future. b, The extremity of the cuneiform process, where it joins the sphenoid bone. c c, The two condyloid processes, which articulate the head with the spine. d d, The prints made by the posterior lobes of the brain. e e, The prints made by the lobes of the cerebellum. f, The cruciform ridge. g, The foramen magnum, through which the spinal marrow passes. h, The foramen linguale, for the passage of the ninth pair of nerves.

a, The upper edge which forms the squamous future. b, The pars mammillaris. c, The pars petrosa. d, The zygomatic process. e, The styloid process. f, The entry of the auditory nerve.

a a, The temporal processes. b b, The pterygoid processes. c c, The spinous processes. d d, The posterior clinoid processes. e e, The anterior clinoid processes. f, The sella turcica, for lodging the glandula pituitaria. g, The anterior process, which joins the ethmoid bone.

a, The pars plana, which forms part of the orbit. b, The os spongiosum superius. c, The nasal lamella. d, The ethmoid cells. e, Crista galli.

a, Their superior sides. b, Their inferior sides. c, Their exterior sides. d, Their joining.

a, The orbital part. b, The lachrymal part. c, The furrow between these two convex parts.

a, The superior orbital process. b, The inferior orbital process.

c, The malar process. d, The zygomatic process. e, The internal orbital process.

a, The nasal process. b, The tuber, at the top of which is the orbital process, and within it, k, The antrum maxillare. c, The nasal spine. d, The os spongiosum inferius. e, The palate-plate. f, The os palati. g, The two dentes incisores. h, The dens caninus. i, The five dentes molares.

a, The palate-plate. b, The pterygoid process. c, The nasal lamella. d, The orbital process.

a, The substance in the middle of the chin. b, The base. c, The angle. d, The coronoid process. e, The condyloid process. f, The entry of the nerve and blood-vessels. g, The five molares.

a, The fibres of the enamel. b, The osseous part. c, The entry at the point of the root, to d, The channel for the nerve and blood-vessels.

A A A, The two tables of the skull, with the diploe. B B, The orbital processes of the frontal bone. C, The crista galli, with the cribriform-plate of the ethmoid bone on each side of it. D, The cuneiform process of the os occipitis. E, The cruciform ridge. F, The foramen magnum for the passage of the medulla spinalis. G, The zygoma, made by the joining of the zygomatic processes of the os temporum and occipitis. H, The pars squamosa of the os temporum. I, The pars mammillaris. K, The pars petrosa. L, The temporal process of the sphenoid bone. M, The anterior clinoid process of the right side. N, The posterior clinoid process of the right side, and between them, O, The sella turcica. 1, The foramen opticum of the left side. 2, The foramen lacerum. 3, The foramen rotundum.

A A, The two tables and diploe of the frontal and occipital bones. B, The coronal future. C, The serrated edges of the parietal, for forming the sagittal future. D, The lambdoid future. E, The squamous future.

future. F, The furrows made by the vessels of the dura mater. G, The frontal sinus. H, The crista galli. I, The nasal lamella of the ethmoid bone. K, The temporal process of the sphenoid bone. L, The sella turcica. M, The sphenoid sinus. N, The vomer. O, The palate-plate of the superior maxillary bone; and from it the processus alveolaris, which contains the teeth. P, The os nasi. Q, The passage into the left nostril. 1. The meatus auditorius internus, for the passage of the auditory nerve. 2. The passage of the ninth pair of nerves. 3. The foramen incisivum.

FIG. 17. The external surface of the base of the CRANIUM and UPPER JAW.

A A, The lambdoid future. B, The superior horizontal ridge of the occipital bone, which is opposite to the cruciform ridge, where the superior longitudinal

sinus divides to form the lateral sinuses. C, The perpendicular ridge. D, The inferior horizontal ridge. E, The foramen magnum, for the passage of the medulla spinalis. F F, The two condyles. G, The cuneiform process. H H, The zygomatic process of the temporal bone. I I, The mastoid processes. K, The vomer, which forms the back-part of the septum nasi. L L, The styloid processes. M M, The fossæ at the root of the mastoid processes, for the posterior belly of the digastric muscle. N N, The cavities for receiving the condyles of the lower jaw. O O, The ossa palati. P, The longitudinal palate-future. Q, The transverse palate-future. R, The alveoli, or spongy sockets for the teeth. S, The zygomatic process of the ossa malarum. T T, The zygomatic future. 1. Meatus auditorius externus. 2. Hole for the internal carotid artery. 3. For the artery of the dura mater. 4. Foramen ovale, for the third branch of the fifth pair, to the upper jaw.

EXPLANATION OF PLATE XIV.

FIG. 1. A posterior view of the STERNUM and CLAVICLES, with the ligament connecting the clavicles to each other.

a, The posterior surface of the sternum. b b, The broken ends of the clavicles. c c c c, The tubercles near the extremity of each clavicle. d, The ligament connecting the clavicles.

FIG. 2. A fore view of the LEFT SCAPULA, and of a half of the CLAVICLE, with their ligaments.

a, The spine of the scapula. b, The acromion. c, The inferior angle. d, Inferior costa. e, Cervix. f, Glenoid cavity, covered with cartilage for the arm-bone. g g, The capsular ligament of the joint. h, Coracoid process. i, The broken end of the clavicle. k, Its extremity joined to the acromion. l, A ligament coming out single from the acromion to the coracoid process. m, A ligament coming out single from the acromion, and dividing into two, which are fixed to the coracoid process.

FIG. 3. The joint of the elbow of the LEFT ARM, with the ligaments.

a, The os humeri. b, Its internal condyle. c c, The two prominent parts of its trochlea, appearing through the capsular ligament. d, The ulna. e, The radius. f, The part of the ligament including the head of the radius.

FIG. 4. The BONES of the RIGHT-HAND, with the PALM in view.

a, The radius. b, The ulna. c, The scaphoid bone of the carpus. d, The os lunare. e, The os cuneiforme. f, The os pisiforme. g, Trapezium. h, Trapezoides. i, Capitatum. k, Unciforme. l, The four metacarpal bones of the fingers. m, The first

phalanx. n, The second phalanx. o, The third phalanx. p, The metacarpal bone of the thumb. q, The first joint. r, The second joint.

FIG. 5. The posterior view of the BONES of the LEFT HAND.

The explication of Fig. 4. serves for this figure; the same letters pointing the same bones, though in a different view.

FIG. 6. The upper extremity of the TIBIA, with the femilunar cartilages of the joint of the knee, and some ligaments.

a, The strong ligament which connects the rotula to the tubercle of the tibia. b b, The parts of the extremity of the tibia, covered with cartilage, which appear within the femilunar cartilages. c c, The femilunar cartilages. d, The two parts of what is called the cross ligament.

FIG. 7. The posterior view of the joint of the RIGHT KNEE.

a, The os femoris cut. b, Its internal condyle. c, Its external condyle. d, The back-part of the tibia. e, The superior extremity of the fibula. f, The edge of the internal femilunar cartilage. g, An oblique ligament. h, A larger perpendicular ligament. i, A ligament connecting the femur and fibula.

FIG. 8. The anterior view of the joint of the RIGHT KNEE.

b, The internal condyle. c, Its external condyle. d, The part of the os femoris, on which the patella moves. e, A perpendicular ligament. f f, The two parts of the crucial ligaments. g g, The edges of the two moveable femilunar cartilages. h, The tibia. i, The

i, The strong ligament of the patella.—The back-part of it where the fat has been dissected away. l, The external depression. m, The internal one. n, The cut tibia.

FIG. 9. A view of the inferior part of the bones of the RIGHT FOOT.

a, The great knob of the os calcis. b, A prominence on its outside. c, The hollow for the tendons, nerves, and blood-vessels. d, The anterior extremity of the os calcis. e, Part of the astragalus. f, Its head covered with cartilage. g, The internal prominence of the os naviculare. h, The os cuboides. i, The os cuneiforme internum; k, —Medium; l, —Externum. m, The metatarsal bones of the four lesser toes. n, The first—o, The second—p, The third phalanx of the four lesser toes. q, The metatarsal bones of the great toe. r, Its first—s, Its second joint.

FIG. 10. The inferior surface of the two large SESAMOID BONES, at the first joint of the great toe.

FIG. 11. The superior view of the bones of the RIGHT FOOT.

a, b, as in Fig. 9. c, The superior head of the astragalus. d, &c. as in Fig. 9.

FIG. 12. The view of the SOLE of the FOOT with its ligaments.

a, The great knob of the os calcis. b, The hollow for the tendons, nerves, and blood-vessels. c, The sheaths of the flexores pollicis and digitorum longi opened. d, The strong cartilaginous ligament supporting the

head of the astragalus. e, h, Two ligaments which unite into one, and are fixed to the metatarsal bone of the great toe. f, A ligament from the knob of the os calcis to the metatarsal bone of the little toe. g, A strong triangular ligament, which supports the bones of the tarsus. i, The ligaments of the joints of the five metatarsal bones.

FIG. 13. a, The head of the thigh-bone of a child. b, The ligamentum rotundum connecting it to the acetabulum. c, The capsular ligament of the joint with its arteries injected. d, The numerous vessels of the mucilaginous gland injected.

FIG. 14. The back view of the cartilages of the LARYNX, with the OS HYOIDES.

a, The posterior part of the base of the os hyoides. b b, Its cornua. c, The appendix of the right side. d, A ligament sent out from the appendix of the left side, to the styloid process of the temporal bone. e, The union of the base with the left cornu. f f, The posterior sides of (g) the thyroid cartilage. h h, Its superior cornua. i i, Its inferior cornua. k, The cricoid cartilage. l l, The arytenoid cartilages. m, The entry into the lungs, named glottis. n, The epiglottis. o o, The superior cartilages of the trachea. p, Its ligamentous back-part.

FIG. 15. The superior concave surface of the SESAMOID BONES at the first joint of the great toe, with their ligaments.

a, Three sesamoid bones. b, The ligamentous substance in which they are formed.

P A R T II.

O F T H E M U S C L E S.

SECT. I. Of the MUSCLES in general.

THE muscles are bundles of fibres of different figures and sizes, and for the most part consisting of two different portions; one whereof is thick, soft, and more or less red, forming what is called the body, fleshy substance, or belly of the muscle. The other is thin and small, of a close texture, and very white, forming the extremities, termed by anatomists tendons or aponeuroses. Both portions are covered by a particular membrane.

The fibres are, for the most part, ranked in fasciculi, in a lateral situation with respect to each other, and distinguished by membranous, cellular, or adipose septa, as by so many particular vagines.

These fibres are connected to each other, and to the intermediate septa, by a great number of very small fine filaments, the capillary extremities of arteries, veins, and nerves running over them; and they are inclosed in a thin membranous, cellular covering, called the proper membrane of the muscle, being a continuation of the septa or vaginæ already mentioned.

The disposition of the fibres is various: some are disposed like radii; others form planes more or less incurvated; and some form complete circumferences, the two extremities meeting and uniting together.

The difference of muscles is very considerable, and depends on many circumstances; the chief of which are, the size, figure, direction, situation, structure, connection, and use; and it is from these differences that the names of the greatest part of the muscles are taken.

From

From their size they are termed great, middle, small, long, broad, thin: From their figure, triangular, fealious, square, &c. From their direction, straight, oblique, transverse. From their situation, superior, inferior, external, &c.

With respect to their structure, muscles are either simple or compound. Simple muscles are those whose fleshy fibres, or rather the fleshy portions of their moving fibres, are all uniformly disposed, and terminate in tendons lying either in a straight or oblique line.

Compound muscles are those whose fleshy fibres are disposed obliquely in several particular ranks, representing the same number of simple muscles, with their fibres, lying in opposite directions. In proportion to the number of these ranks or series, the muscle is said to be more or less compounded.

When the compound muscle is made up of two simple muscles only, these are so disposed as to represent a feather, and the compound muscle is from thence termed penniform.

Some are made up of two muscles more or less, in a lateral situation with respect to each other, and united at one extremity: others are made up of three or four muscles, situated in the same manner; and if they are united at that extremity which the ancients called the head of the muscle, they are called bicipites, tricipites, &c. according to the number of these heads; but if they are joined at the other extremity, they are termed bicornes, tricornes, &c.

The muscles are fixed by their extremities to different parts, and in different places of the human body. The greatest part of them are inserted in bones alone. Some are fixed partly to bones, and partly to cartilages; as those of the ear and nose: some partly to bones, and partly to the integuments; as several muscles of the face.

The names taken from the connections and insertions of muscles are generally of two kinds; one common, and referred to some considerable part of the body; as when we say, the muscles of the head, of the thorax, abdomen, &c.; the other proper, specifying more particularly the insertions of each muscle, as the massoideus, sterno-massoideus, &c.

The general use of the muscles is to move all the parts of the body, whether hard, soft, or fluid. Most of the hard and soft parts are moved by these powers being fixed to them, and they move the rest without any such insertion.

The action of the muscles in general, consists chiefly in the contraction or shortening of their fleshy portion; by which the extremities of the muscle are brought nearer to each other, and consequently the parts are moved to which these extremities are fixed.

The principal phenomena of muscular action are these: The fleshy portion appears harder and more swelled in the time of action than of inaction, as may be readily perceived by touching it in both states: The hardness of this swelling increases in proportion as the motion is continued, as is likewise evident by the touch; and it likewise increases by merely adding to the weight or resistance of the part moved, though its situation does not continue to be changed.

SECT. II. The MUSCLES of the Abdomen.

By the muscles of the abdomen, or lower belly, we mean those which form principally the sides or circumference of that cavity. They are commonly ten in number, five on each side; eight whereof are very large, the other two very small.

OBLIQUUS EXTERNUS.

The obliquus externus is a broad thin muscle, fleshy on its upper and back-part, and tendinous on the anterior and greatest portion of the lower part. It reaches from half the lateral and inferior part of the thorax, to almost half the lateral and superior part of the pelvis; and from the back-part of the regio lumbaris to the linea alba.

It is fixed, by its upper part, to the ribs; by the lower, to the os ilium, ligamentum Fallopii, and os pubis; and, by the fore-part, to the linea alba. The posterior portion next the vertebrae of the loins has commonly no true muscular insertions.

OBLIQUUS INTERNUS.

The internal oblique is a broad thin muscle like the former, having nearly the same extent and insertions; that is, in the lower ribs above; in the crista of the os ilium and ligamentum Fallopii, below; and in the linea alba, before: but it differs from it in this, that its lower part is more fleshy than the upper.

One portion of its lower extremity, which is entirely fleshy, is fixed, by very short tendinous fibres, in the middle space between the two labia of the crista osi ilium, from the back-part of the tuberosity of that crista, near the symphysis of the os sacrum, almost all the way to the superior and anterior spine of the os ilium; so that its insertion reaches farther back than that of the external oblique.

The fleshy fibres thus fixed, run up first a little obliquely from behind forward, and then this obliquity increases proportionably as the fibres lie more anteriorly, and they cross those of the fleshy portion of the external oblique, being afterwards inserted exteriorly in the lower edges of the cartilages of all the false ribs, and those of the two lowest true ribs, reaching to the extremity of the cartilago ensiformis.

This muscle is likewise called obliquus descendens, for the same reason that the former is termed ascendens, obliquus inferior, and obliquus minor, because it does not reach so high, and is not quite so large as the external oblique.

MUSCULI RECTI.

The recti are long narrow muscles, thicker than the obliqui. They lie near each other like two large bands, from the lower part of the thorax, to the os pubis, the linea alba coming between them. Their breadth diminishes, and their thickness increases gradually from above downward.

The

This anatomical drawing shows the muscles of the human head and neck from a lateral perspective. The labels include: a (forehead), b (side of head), c (ear), d (nose), e (cheek), f (jaw), g (chin), h (throat), i (neck), j (upper neck), k (lower neck), l (sternocleidomastoid), m (platysirrhoid), n (sternohyoid), o (sternothyroid), p (thyrohyoid), q (cricoid), r (cricothyroid).

This anatomical drawing shows the muscles of the human head and neck from a lateral perspective. The labels include: a (forehead), b (side of head), c (ear), d (nose), e (cheek), f (jaw), g (chin), h (throat), i (neck), j (upper neck), k (lower neck), l (sternocleidomastoid), m (platysirrhoid).

This central anatomical drawing depicts the entire human body from a full-body perspective, highlighting the musculature. The labels are distributed across the body: A (forehead), B (side of head), C (ear), D (nose), E (cheek), F (jaw), G (chin), H (throat), I (neck), J (upper neck), K (lower neck), L (sternocleidomastoid), M (platysirrhoid), N (sternohyoid), O (sternothyroid), P (thyrohyoid), Q (cricoid), R (cricothyroid), S (trapezius), T (deltoid), U (biceps brachii), V (pectoralis major), W (latissimus dorsi), X (triceps brachii), Y (brachialis), Z (anconeus), a (forearm), b (hand), c (wrist), d (elbow), e (upper arm), f (forearm), g (hand), h (wrist), i (thigh), j (leg), k (ankle), l (foot), m (toe), n (knee), o (hip), p (thigh), q (leg), r (ankle), s (foot), t (toe), u (heel), v (calf), w (ankle), x (foot), y (toe), z (heel).

This anatomical drawing shows the muscles of the human head and neck from a lateral perspective. The labels include: a (forehead), b (side of head), c (ear), d (nose), e (cheek), f (jaw).

This anatomical drawing shows the muscles of the human head and neck from a lateral perspective. The labels include: a (forehead), b (side of head), c (ear), d (nose).

The superior extremity of each muscle is fixed to a part of the lower extremity of the sternum, to the three lowest true ribs, and to the first false rib, by the same number of digitations, of which that which is farthest from the sternum is the broadest.

The body of the muscle lies in the vagina, formed by the aponeurosis of the broad muscles of the abdomen. Exteriorly, it is divided into several portions, resembling distinct muscles placed endways, by transverse tendons, termed ennervations, which commonly are all above the umbilicus, very seldom below it, and they adhere very close to the vagina.

The lower extremity of this muscle is narrower than the upper, and ends in a thin tendon fixed in the internal labium of the upper edge of the os pubis, near the symphysis, and there it touches the tendon of the other rectus.

MUSCULI PYRAMIDALES.

At the lower part of the recti, we meet commonly with two small muscles, which at first seem to be a portion or appendix of the former. They are named pyramidales from their figure; and by Fallopius, succenturiati.

At the lower extremity, they are broad and thick, being there fixed to the upper edge of the ossa pubis, immediately before the recti. They decrease gradually in breadth and thickness as they ascend, and end by a point in the linea alba, a little way below the umbilicus.

TRANSVERSALES.

THE transverse muscles are nearly of the same breadth with the obliques. Each of them is fixed to the ribs above; below, to the os ilium, and ligamentum Fallopii; before, to the linea alba; and behind, to the vertebrae.

The upper part of this muscle is fixed to the lower part of the inner surface of the cartilages of the two lowest true ribs, and of all the five false ribs, by fleshy digitations, the fibres of which run more or less transversely toward the linea alba, at some distance from which they become tendinous.

The middle part is fixed to the three first vertebrae of the loins, by a double aponeurosis, or two tendinous planes, one internal or anterior, the other external or posterior.

The inferior part of this muscle is fixed by an insertion wholly fleshy to the internal labium of the crista ossis ilium, and to a great part of the ligamentum Fallopii. From thence many of its fibres run towards the linea alba, the rest to the os pubis, all of them becoming more or less tendinous before their insertion.

USES OF THE ABDOMINAL MUSCLES.

The common uses are, to sustain the viscera of the abdomen, and to counterbalance the perpetual motions of ordinary respiration, and thereby gently and continually to act on the viscera; which action may be reckoned a

sort of trituration, of great importance to the animal economy. They compress the abdomen, in order to clear it of what ought to pass off by the natural outlets; to relieve the stomach, by vomiting, from whatever might be hurtful to it; and, lastly, to drive out, by a violent expiration, whatever may incommodate the organs contained in the thorax.

The musculi recti serve to support the trunk of the body when inclined backward, and to bend or bring it forward again; to raise the body up when lying; and, lastly, to climb.

The pyramidales seem only to assist the action of the recti; though, when we consider the oblique direction of their fibres toward the linea alba, there may be some reason to think that they compress the bladder, especially when very full of urine.

The transversales seem to have no other use than that of bracing or girding the abdomen in different degrees.

SECT. III. The MUSCLES which move the Bones of the Shoulder upon the Trunk.

TRAPEZIUS.

THE trapezius is a large, broad, thin, fleshy plane, situated between the occiput and lower part of the back, and from thence extending to the shoulder, in the figure of a large irregular square. From this figure the ancient Greeks took its name, and, together with the trapezius of the other side, it forms a kind of lozenge.

Above, it is fixed in the superior transverse line of the os occipitis, by a thin series of fleshy fibres, reaching to the musculus occipitalis, and appearing to cover that muscle by a kind of aponeurosis. Behind, it is fixed to the five superior spinal apophyses of the neck, by means of the posterior cervical ligament, and immediately to the extremities of the two lowest spinal apophyses of the neck, and of all those of the back.

This muscle covers immediately the splenius or massoideus superior, part of the complexus major, the angularis, rhomboides, and part of the latissimus dorsi.

RHOMBOIDES.

THIS muscle is a thin, broad, and obliquely square fleshy plane, situated between the basis of the scapula and the spina dorsi; and it is from its figure that it has been termed rhomboides.

It may be divided into two portions, one superior, the other inferior, which sometimes appear separate. The superior portion is fixed, by an insertion wholly fleshy, in the two or three lowest spinal apophyses of the neck, and partly in the posterior cervical ligament. The inferior portion is fixed, by a tendinous plane, in the three or four uppermost spinal apophyses of the back.

These two portions, of which the inferior is by much the broadest, being united, are inserted in the edge of the basis scapulae, from the small triangular space to the inferior angle, the superior portion covering a small part of the insertion of the angularis.

This whole muscle is covered by the trapezius, and covers immediately the ferratus posticus superior, being joined to each of these muscles by a filamentary or cellulosous substance.

ANGULARIS, VULGO LEVATOR SCAPULÆ PROPRIUS.

This is a long, and pretty thick muscle, about two fingers in breadth, lying above the superior angle of the scapula, along the posterior lateral part of the neck of that bone.

It is inserted above in the extremities of the transverse apophyses of the four first vertebrae of the neck, by four fleshy branches, ending in short tendons; sometimes the second, sometimes the third, or both, and sometimes the fourth of these branches, is wanting; these defects being made up by the largeness of the rest.

From thence these branches run down a little obliquely, and then uniting together, they are inserted in the superior angle of the scapula, and in the edge of its basis, from thence to the small triangular space, being there covered a little by the rhomboides.

This muscle is easily divided into two through its whole length. It is covered by the trapezius, and its insertions in the neck are sometimes mixed with those of the neighbouring muscles.

PECTORALIS MINOR.

THIS is a small fleshy muscle, something of a triangular shape, situated at the superior, lateral, and anterior part of the thorax.

By its basis it is inserted in the external labium of the upper edge of the second, third, fourth, and fifth true ribs; near their union with the cartilages, by the same number of digitations or separate fleshy portions, because of the intervals between the ribs; and for that reason it has been called ferratus minor anticus.

From thence these portions run up, more or less, obliquely toward the shoulder, and form a fleshy belly, which contracts as it passes before the two first ribs, and then becoming a short, flat, and broad tendon, is inserted in the upper part of the apophysis coracoides of the scapula, reaching all the way to the point of that process.

This muscle is covered by the pectoralis major, and adheres very closely to the external intercostal muscles.

SERRATUS MAJOR.

THIS is a broad, fleshy, and pretty thick muscle, lying on the lateral part of the thorax, between the ribs and scapula, by which it is covered. Its figure is that of an irregular square, its greatest breadth being in the back-part, where it terminates by digitations of unequal lengths, in a radiated disposition, their extremities describing an arch or curve; and from these digitations its name is taken.

It is inserted backward in the interal labium of all the basis of the scapula, from the superior to the inferior angle. From thence running forward wholly fleshy, it

increases gradually in breadth, and is inserted in all the true ribs, and often in one or two of the false ribs, by the same number of digitations.

SUBCLAVIUS.

THIS is a small oblong muscle, lying between the clavicle and first rib. It is fixed by one end in all the middle lower portion of the clavicle, at the distance of about an inch from each extremity; and by the other in the cartilage and a small part of the bone of the first rib. It seems likewise to adhere to the extremity of the clavicle next the sternum, by a kind of broad thin ligament.

USES of the MUSCLES which move the BONES of the SHOULDER on the TRUNK.

THE mechanism of the scapula, in relation to its motions and changes of situation, is very different from that of all the other bones of the body, except the os hyoides. All the other bones have solid fulcra or fixed points, on which they are either moved or fixed by the muscles; but the motions of the scapula, its changes of situation, and its continuance in any one given attitude, are brought about without the help of any solid fulcrum. The muscles alone sustain it and brace it down, in all its different motions and situations.

The scapula has this peculiarity likewise belonging to it, that it is the fulcrum and basis of all the motions of the os humeri, of some motions of the fore-arm, and even of all the most violent efforts made with these bones, without being itself either moved or fixed on any solid basis.

The use of the trapezius is to raise the shoulder, and to keep it from sinking.

The ferratus major raises the shoulder or top of the scapula, brings it forward, and hinders it from sinking. In all these, it is the principal actor; and it is impossible to conceive how labourers raise and support, by the shoulder alone, the heavy burdens with which they are loaded, without the assistance of this muscle.

According to the insertions and direction of the rhomboides, its general use must be, to draw backward and upward the sub-spinal portion of the basis scapule.

It is likewise a moderator to the trapezius and ferratus major, when they raise the shoulder, or carry the acromium upward; and it brings the scapula back to its natural situation, when the action of these muscles ceases.

The angularis, by its insertion in the superior angle of the scapula, moderates the descent of that angle, while the trapezius and ferratus major raise the acromium. Afterwards, when these two muscles cease to act, the angularis raises the superior angle, and by that means depresses the acromium.

The pectoralis minor assists the rhomboides and angularis, as moderators of the action of the trapezius and ferratus major, in turning the point of the acromium upward, the superior angle downward, and the inferior angle forward.

It is likewise an assistant to the rhomboides and angularis, in restoring the scapula to its natural situation, when

when the trapezius and serratus major cease to act; by drawing downward the apophysis coracoides, in which it is inserted.

The subclavius can have no other ordinary use, but to bring down the clavicle, after it has been raised, together with the acromium, by the action of the trapezius and serratus major.

SECT. IV. The MUSCLES which move the Os Humeri on the Scapula.

DELTOIDES.

THIS is a very thick muscle, covering the upper part of the arm, and forming what is termed the stump of the shoulder. It is broad above, and narrow below, in a triangular form; and its name is taken from the resemblance it bears to the Greek letter $\backslash Delta$ delta.

It is made up of eighteen or twenty small single muscles, in an opposite situation with respect to each other, and united by middle tendons; so that, taken all together, they form several penniform muscles. The outer surface appears almost wholly fleshy, but on the inner surface we see the several tendons.

Above, it is fixed in the whole inferior labium of the spina scapulae, in the convex or long edge of the acromium, and in the third part of the anterior edge of the clavicle next that apophysis. It surrounds the angle formed by the articulation of these two bones, by a particular slope and fold contrived for that purpose.

From thence it runs down above one third of the length of the os humeri, where it is inserted, by a thick tendon, in the large muscular rough impression below the bony ridge which goes from the great tuberosity of the head of the bone.

PECTORALIS MAJOR.

THIS is a large, thick, and fleshy muscle, covering the fore-part of the breast, from the sternum, where it is very broad, to the axilla, where it contracts in its passage to the arm.

The insertions in the sternum end by a great number of very short tendons which run toward the middle of the bone, meeting and decussating those from the same muscle on the other side. The lower insertions are most distinctly digitated, and they mix with those belonging to the rectus and obliquus externus of the abdomen, there being likewise several fasciculi of fibres common to the pectoralis with these muscles. This portion is also fixed to the ribs by internal fleshy strata covered by the external insertions, and forming, together with them, the thickness of the muscle.

From thence all the fleshy fibres contract in breadth, and approach each other, in their passage to the arm. The superior fibres run downward, joining those of the clavicular portion; those next them run less obliquely; the following more or less transversely; and the inferior run upward, in the same manner.

This muscle, together with the deltoides, sends off

an aponeurosis, which, joining that of the biceps, is spread over the muscles of the arm.

LATISSIMUS DORSI.

THIS is a broad, thin, and mostly fleshy muscle, lying between the axilla, where it is very narrow, and the back on which it expands itself by radiated fibres, both in length and breadth, from the middle of the back all the way to the lower part of the regio lumbaris; and from this situation it has its name.

Its insertions are partly tendinous, and partly fleshy. In the first place, it is sometimes, but not always, fixed in the inferior costa of the scapula near the angle, by a fasciculus of fleshy fibres. In the next place, it is fixed by an aponeurosis, in the spinal apophyses of the six or seven, and sometimes eight lowest vertebrae of the back, in those of all the vertebrae of the loins, in the superior spines and lateral parts of the os sacrum, and in the external labium of the posterior part of the os ilium.

TERES MAJOR.

THIS is a long, thick, flat muscle, situated a little obliquely between the inferior angle of the scapula, and the upper part of the arm.

It is fixed by its posterior fleshy extremity in all the large angular surface on the outside of the scapula, in the inferior costa of that bone, and near the angle. From thence it advances with longitudinal fibres toward the upper quarter of the os humeri, terminating in a broad flat tendon intermixed with some fleshy fibres, which at the upper edge are continued all the way to the insertion, lying in the same place with the tendon.

It is inserted, by its anterior extremity, at the lower part of the bony ridge of the small tuberosity, along the edge of the channel, almost opposite to, and sometimes a little lower than the insertion of the pectoralis major. It lines the cavity of the channel by a tendinous elongation, which joins that from the pectoralis, and seems to be continued with it.

TERES MINOR.

THIS is a very fleshy muscle, resembling the teres major, but narrower and shorter. It lies above the last named muscle, between the costa inferior of the scapula, and the head of the os humeri.

It is fixed by one end to all the middle part of the inferior costa of the scapula, and to the long particular surface immediately above that costa, reaching from the great angular surface near the neck of the bone. From thence it runs wholly fleshy, till it changes into a flat tendon, which is inserted in the posterior or inferior surface of the great tuberosity of the head of the bone, and likewise a little lower down.

INFRA-SPINATUS.

THIS is a triangular, fleshy, and pretty broad muscle, in some measure penniform, filling the whole infra-spinal cavity or fossa of the scapula.

It is fixed in the posterior half of the infra-spinal cavity or fossa, and to the corresponding part of the basis of the scapula.

From thence arise a great number of short fleshy fibres, which run more or less obliquely, and end in a middle tendinous plane, which terminates a little below the broadest part of the spine of the scapula, under the root of the acromium.

Then the fleshy fibres, leaving the bone, unite in one fleshy mass, which, passing under the acromium, over the articulation of the head of the os humeri, and adhering to the capsular ligament, terminates there in a flat broad tendon, which, adhering likewise to the capsula, is afterwards inserted in the greater middle surface of the great tuberosity of the head of the os humeri.

SUPRA-SPINATUS.

THIS is a thick narrow muscle, in some measure penniform, filling all the supra-spinal cavity of the scapula.

It is fixed to all the posterior half of the supra-spinal fossa; and sometimes its insertion reaches near the neck of the bone. There the fibres leave the surface of the bone, and pass between the acromium and neck of the scapula, under the arch formed by the acromium and extremity of the clavicle, and under the ligament between the acromium and apophysis coracoides; being afterwards inserted in the superior surface of the great tuberosity of the head of the os humeri, very near the bony channel.

CORACO-BRACHIALIS.

THIS is a long muscle lying on the inside of the upper half of the os humeri.

It is fixed above to the point of the coracoid apophysis, between the insertions of the biceps and pectoralis minor, by a tendon, which, as it descends, adheres for a good way to the tendons of these two muscles. Afterwards it becomes fleshy, and is inserted by a broad thin extremity, with a small mixture of tendinous fibres, in the middle part of the os humeri.

SUBSCAPULARIS.

THIS muscle is of the same breadth and length with the scapula, of which it occupies all the inner or concave side; and from this situation it has its name. It is thick, and made up of several penniform portions nearly in the same manner with the deltoides.

It is fixed in the internal labium of the whole basis, and in almost the whole internal surface of the scapula; its fleshy portions lying in the intervals between the bony lines, when these are found. Near the neck, they leave the bone, and form a very broad tendon which is inserted in the surface of the small tuberosity of the head of the os humeri.

USES of the MUSCLES which move the OS HUMERI on the SCAPULA.

THE deltoides, from the disposition of its insertions in the scapula and clavicle, may raise the arm, or sepa-

rate it from the ribs, not only directly, but likewise obliquely in many different ways. The arm being lifted directly upward, the lateral, anterior, and posterior portions of this muscle may bring the arm, so raised, forward and backward.

The latissimus dorsi serves in general to bring down the arm when raised; it also serves to depress the shoulder, or to maintain it in that situation against any force that endeavours to raise it; as when we lean upon the elbow in sitting, or walk upon crutches.

The pectoralis major serves in general to bring the arm near the ribs, to press it strongly against them, and to carry it towards the fore-part of the thorax.

The teres major, by being inserted in the os humeri in a direction parallel to the latissimus dorsi, becomes a congener to the superior and posterior portion of that muscle; and accordingly moves the os humeri in the same manner with it. It turns the bone round its axis, when the fore-arm is carried behind the back.

It likewise pulls the arm directly backward, without moving it round its axis.

The coraco-brachialis brings the arm to the fore-side of the thorax, raising it at the same time; and, in this case, it may be reckoned a congener or assistant to the pectoralis major in great efforts; and may perform the same motion by itself, when no great force is necessary; as when the whole arm hangs down, and is moved backward and forward like a pendulum, the motion forward being performed by the coraco-brachialis, and the motion backward by the teres major, its antagonist.

This muscle may likewise move the scapula on the os humeri kept firmly depressed, as when sitting in a chair we take fast hold of the edge of it with the hand. In this case the coraco-brachialis may bring the acromium downward, and the inferior angle of the scapula, near the vertebrae. It serves likewise to bring the arm to its former situation, after it has been turned by the latissimus dorsi, in order to apply the hand to the back; and then it turns the os humeri upon its axis in a contrary direction to that given it by the other muscle.

The supra-spinatus joins with the deltoides in lifting up the arm; this muscle beginning that action, and the deltoides continuing it.

The infra-spinatus being inserted by its tendon in the middle surface of the great tuberosity of the os humeri, must perform different motions according to the different situations of that bone. If it acts while the arm hangs down, parallel to the trunk of the body, it may move the os humeri round its axis, from before outward; and consequently, if the fore-arm be at the same time bent, it will turn the hand from the body, &c.

When the arm hangs down in its natural situation, the subscapularis may turn it round its axis, from without forward, as it happens when in this situation we beat the breast with the fore-arm bent; and it likewise strongly assists the latissimus dorsi, when we turn the hand behind the back.

When the arm being raised, we move it backward, as in giving a back-stroke with the elbow or fist, the subscapularis hinders the head of the os humeri from being luxated forward.

The teres minor may turn the arm when depressed round its axis, from before outward; as it happens when the fore-arm, being bent and applied to the lower part of the breast, is removed from thence, without moving the elbow from the side.

SECT. V. The MUSCLES which move the Bones of the Fore-arm on the Os Humeri.

BICEPS five CORACORADIALIS.

THIS is a double muscle made up of two long fleshy bodies, more or less round, lying by the side of each other, on the middle anterior part, and a little toward the inside of the arm. These two bodies are separated above, each of them ending in a small tendon. As they run down they become contiguous, and afterwards closely united by one common broad tendon.

It is fixed by one of the superior tendons, in the apex of the coracoid apophysis of the scapula.

The other superior tendon is smaller and longer than the former, and the fleshy body belonging to it shorter and more compounded. This tendon is lodged in the bony channel of the os humeri, being surrounded by a membranous vagina continued from the capsular ligament, and ending at the fleshy body where it is entirely closed.

BRACHIÆUS.

THIS is an oblong, thick, and broad muscle, lying immediately on the anterior part of the lower half of the os humeri. The upper part of it is forked or sloped, and at the bending of the joint of the elbow the lower part contracts.

It is fixed to the surface of the os humeri by a great number of fleshy fibres, from the lower insertion of the deltoides, almost down to the two fossæ at the lower extremity of the bone, and from one edge of the fore-side of this lower extremity to the other. The fibres are for the most part longitudinal, those nearest the surface of the muscle being longest, the more internal growing gradually shorter.

ANCONÆUS MAJOR.

THIS is a long fleshy muscle lying on the backside of the os humeri.

It is fixed above by a short tendon to the inferior impression in the neck of the scapula, and to a small part of the inferior costa of that bone. From thence it passes between the extremities of the subscapularis and teres minor, and, having reached the backside of the lower extremity of the os humeri, it ends obliquely in a strong broad tendon, which, adhering closely in the capsular ligament, is afterwards fixed by a broad insertion in the rough tuberosity on the upper side of the olecranium.

ANCONÆUS EXTERNUS.

THIS is a long muscle lying on the outer part of the

backside of the os humeri, from its neck to the external condyle.

It is fixed above in the neck of the os humeri under the inferior surface of the great tuberosity, and under the insertion of the teres minor, but a little more backward. It is likewise fixed by some oblique fibres in the external inter-muscular ligament.

ANCONÆUS INTERNUS.

THIS muscle is shorter and more fleshy than the anconæus externus, and lies toward the inner part of the lower half of the os humeri.

It is fixed above, under the lower extremity of the teres major, but a little more backward, and to the internal inter-muscular ligament, which makes a kind of septum between this muscle and the brachæus. From thence the fibres contracting in breadth, pass toward the tendon of the anconæus major, some of them running in between it and the bone, and are inserted in the edge and inner side of that tendon.

ANCONÆUS MINOR.

THIS is a small muscle obliquely triangular, lying in the oblong fossula on the outside of the olecranium.

It is fixed by a small, but pretty strong tendon, in the lower part of the external condyle of the os humeri. From thence the fleshy fibres run down obliquely in a radiated form, and are inserted in the bottom and whole posterior edge of the fossula already mentioned.

USES of the Muscles which move the Bones of the Fore-arm on the Os Humeri.

THE biceps, or coraco-radialis, bends both bones of the fore-arm, and turns the radius upon the ulna; performing both motions by its insertion in the radius alone. It likewise moves the os humeri on the fore-arm, the scapula on the os humeri, and the os humeri on the scapula.

The brachæus serves to bend the fore-arm on the os humeri, by its insertion in the ulna, and by the connection of that bone with the radius. It serves also to move the os humeri on the fore-arm.

The anconæus maximus serves to extend the fore-arm, by bringing the ulna to a straight line with the os humeri. It serves likewise to extend the os humeri on the ulna, when the last named bone is fixed by some exterior resistance, as when, being laid upon the ground, we rise by supporting ourselves on our hand. In this case likewise, the scapula must be kept steady by the coraco-brachialis.

The two lateral anconæi co-operate with, and assist the anconæus maximus, in extending the fore-arm on the os humeri, and the os humeri on the fore-arm.

The anconæus minimus may concur with the other muscles of that name, in extending the fore-arm on the os humeri, and the os humeri on the fore-arm; but its action does not reach to all the degrees of flexion of these bones; for when the fore-arm is very much bent, if we

examine carefully the situation of this muscle, we will find it more disposed to maintain these bones in that posture, by co-operating with the brachialis, than to extend them by assisting the other anconæ.

SECT. VI. The MUSCLES which move the Radius upon the Ulna.

SUPINATOR LONGUS sive MAJOR.

THIS is a long flat muscle, lying on the external condyle of the os humeri, and on the convex side of the radius from one end to the other.

It is fixed by fleshy fibres to the external inter-muscular ligament, and to the crista of the external condyle of the os humeri, for five or six fingers breadth above the condyle, between the brachiseus and anconæ externus. From thence it runs along the whole convex side of the radius, and is inserted by a flat narrow tendon, a little above the styloid apophysis in the angle between the concave and flat sides of the extremity of this bone.

SUPINATOR BREVIS sive MINOR.

THIS is a small thin fleshy muscle, surrounding a great portion of the upper third part of the radius.

It is fixed by one end to the lower part of the external condyle of the os humeri, to the external lateral ligament of the joint, to the annular ligament of the radius, and to part of the lateral eminence in the head of the ulna.

From thence it passes obliquely over the head of the radius, covering some part of it; and running down upon, and in some measure surrounding the neck, it turns in under the bicipital tuberosity, and is inserted by the side of the interosseous ligament in the inside of the superior quarter of the bone, and even a little lower.

PRONATOR TERES sive OBLIQUUS.

THIS is a small muscle, broader than it is thick, situated on the upper part of the ulna opposite to the supinator brevis.

It is fixed to the internal condyle of the os humeri, partly by fleshy fibres, and partly by a tendon common to it with the ulnaris internus. From thence it passes obliquely before the extremity of the tendon of the brachiseus, and reaches to the middle part of the convex side of the radius, where it becomes flat, and is inserted below the supinator brevis by an extremity almost wholly fleshy.

PRONATOR QUADRATUS sive TRANSVERSUS.

THIS is a small fleshy muscle nearly as broad as it is long, lying transversely on the inside of the lower extremity of the fore-arm.

It is fixed by one side or edge in the long eminence at the lower part of the internal angle of the ulna, and by

the other in the broad concave side of the lower extremity of the radius.

It has a ligamentary or tendinous frænum belonging to it, one end of which is fixed in the interosseous ligament, the other in the inner edge of the basis of the radius.

The USES of the Muscles which move the Radius on the Ulna.

THE supinator longus assists in the motion of supination, and is also a flexor of the fore-arm.

The supinator brevis seems to have no other use than what is expressed by its name; and as it is a short small muscle, it must be very weak.

The pronator teres can have no other action but that of pronation, in the different situations of the radius, whether that bone be in a middle state between pronation and supination, or in the greatest degree of supination; and, in this case, though it is but a small weak muscle, it overcomes the supinator longus.

The pronator quadratus is capable of no other motion but pronation, and it acts with much more force than its congeners the pronator teres.

SECT. VII. The MUSCLES which move the Carpus upon the Fore-arm.

ULNARIS.

THIS is a long muscle, fleshy at its upper extremity, and tendinous at the other, situated on the outer part of the ulna.

It is fixed by its upper part in the backside of the long or internal condyle of the os humeri, in that part of the olecranium which is next the condyle, along the upper half of the ulna very nearly; and to the middle common tendon of the neighbouring muscle, termed commonly profundus.

It runs in the direction of the external angle of the ulna, and ends by a long tendon, in the os pisiforme or orbiculare of the carpus, reaching likewise to the os unciiforme, being united to the ligament common to these two bones.

RADIALIS INTERNUS.

THIS is a long muscle very like the foregoing, but situated more obliquely.

Its fleshy portion is fixed, by a short tendon, to the outer and upper side of the inner condyle of the os humeri. From thence it passes obliquely toward the radius; and running along about two thirds of that bone, it forms a long tendon, which passes under a particular annular ligament, and under the insertion of the musculus thenar.

This tendon is at length inserted chiefly in the inside of the basis of the first metacarpal bone, and often in the second likewise, and a little in the first phalanx of the thumb, having first passed through the channel of the os trapezium, which sustains the thumb.

ULNARIS.

THIS is a long muscle lying on the outside of the fore-arm, fleshy toward the os humeri, and tendinous toward the carpus.

It is fixed above to the external condyle of the os humeri, being there united to the anconeus minor, to the annular ligament of the head of the radius, and to the upper half of the external angle of the ulna. From thence it advances, and forms a tendon, which passes through the external notch at the lower extremity of this bone, on one side of the styloid apophysis.

The tendon, having afterward passed under a particular ligament situated near the os cuneiforme of the carpus, is inserted in the outside of the basis of the fourth metacarpal bone, sending some tendinous filaments to the basis of the little finger.

THESE are two muscles closely united together, lying along the external angle of the radius, between the os humeri and the carpus, being fleshy near the former, and tendinous near the latter.

The first is inserted above, in the crista of the external condyle of the os humeri, below the insertion of the supinator longus. The second is inserted in the same condyle below the insertion of the first; and in the neighbouring articular ligament. From thence the two fleshy bodies run down very close together; and having reached the middle of the outside of the radius, each of them terminates in a long tendon.

The two tendons accompany each other to the extremity of the radius; and, having passed under a particular annular ligament, they are divided as it were into two cornua; from whence the ancients, who looked upon them as one muscle, gave it the name of bicornis.

One of these tendons is inserted anteriorly in the basis of the first metacarpal bone, the other nearly in the same place of the second bone.

THIS is a small muscle, lying between the os humeri and the carpus, on the inside of the fore-arm; its body being small and slender, its tendon very long and flat.

It is fixed by its fleshy portion, in the small crista of the inner condyle of the os humeri, sometimes closely united to the ulnaris internus. From thence it runs down fleshy for some space, turning a little obliquely towards the middle of the fore-arm, and ends in a long, narrow, thin tendon.

This tendon passes down the middle of the fore-arm, over all the other muscles to which it slightly adheres, and advancing over the large internal annular or transverse ligament of the carpus, is inserted in the surface thereof, sending off some radiated filaments to the aponeurosis palmaris.

THIS muscle is a small thin plane of fleshy fibres, situated transversely, or more or less obliquely, under the

skin of the large eminence in the palm of the hand, between the carpus and the little finger; its fibres adhering to the skin, and being in some measure interwoven with the membrana adiposa.

These fibres are fixed along the edge of the aponeurosis palmaris, from the large ligament of the carpus toward the little finger; and they run in for some space on the plane of the aponeurosis, but without any connexion with the bones of the metacarpus. Near the aponeurosis, these fibres are more or less tendinous, and some of them often cross each other.

THIS is a very small fleshy muscle, situated obliquely between the large internal annular or transverse ligament of the carpus, and the whole inside of the fourth metacarpal bone.

It is fixed by a small short tendon to the os orbiculare, and to the neighbouring part of the large ligament of the carpus. From thence its fibres run more or less obliquely toward the inside of the fourth metacarpal bone, in the outer edge of which they are inserted. The fibres of this muscle are of unequal lengths, and extend all the way to the articulation of the first phalanx of the little finger with the fourth metacarpal bone, but they have no manner of relation to that finger.

WHEN the ulnaris internus acts alone, or as the principal mover, it brings the hand obliquely toward the internal condyle, and toward the olecranium, though with difficulty.

When it acts together with the radialis internus, it turns the hand equally towards the two extremities of the bones of the fore-arm; and thereby moves not only the carpus in general on the fore-arm, but also the second row of the carpus on the first, and the metacarpal bones on the second.

When it acts with the ulnaris externus, it turns the outer edge of the hand toward the olecranium.

When the ulnaris externus acts with the ulnaris internus, it turns the outer edge of the hand toward the olecranium, as already said.

With the radiales externi, it turns the back of the hand toward the outer condyle.

When this muscle acts alone, it brings the outer edge of the hand obliquely toward the olecranium and the external condyle at the same time.

With the radialis externus, the internus carries the inner edge of the hand, or that next the thumb, toward the extremity of the radius, and toward the fold made by the ulna and os humeri.

Alone, it moves that part of the hand which is next the thumb obliquely, toward the internal angle of the radius.

The radialis externus, together with the radialis internus, turns the inner edge of the hand directly toward the styloid apophysis of the radius.

With

With the ulnaris externus it inverts the hand, turning the convex side of the metacarpus toward the lower extremity of the bones of the fore-arm. It likewise moves the second row of the carpus on the first.

This muscle, acting alone, draws obliquely, and toward the external angle of the radius, that portion of the hand which answers to the first metacarpal bone, and to the index.

The ulnaris gracilis, commonly called palmaris longus, seems to be an assistant to the ulnaris and radialis internus in bending the wrist; and it seems likewise particularly to assist the radialis internus in the motion of pronation.

The metacarpus serves to turn the fourth bone of the metacarpus toward the thumb, and at the same time to increase the convexity of the back of the hand, which is called making Diogenes's cup. The fourth bone thus moved carries the third along with it by reason of their connection, which still augments the hollow on one side, and the convexity on the other.

SECT. VIII. The MUSCLES which move the Fingers.

FLEXOR POLLICIS LONGUS.

THIS is a long muscle, fixed by short and oblique fleshy fibres to the inside of the upper part of the interosseous ligament, near the radius, and along that bone all the way down to the pronator quadratus. There it terminates in a flat tendon.

This tendon having passed under a particular ligament, runs in between the two portions of the thenar, and then into a sort of groove left between the two sesamoide bones fixed to the basis of the second phalanx of the thumb, on that side which is turned to the palm of the hand. Afterwards the tendon ends in the flat side of the third phalanx, near its basis. It is inclosed in a ligamentary vagina, from the annular ligament to its insertion, and it is divided or slit, so that it appears to be inserted by two extremities adhering together by their edges.

EXTENSORES POLLICIS.

THESE are two very distinct muscles, the first or longest of which is sometimes more, sometimes less, and sometimes altogether divided into two, in which case these muscles are three in number. They are situated obliquely between the ulna and convex side of the thumb.

The extensor primus is a long muscle, more or less double, in the manner already said. It is fixed above by fleshy fibres, first to the outside of the ulna, near its upper extremity, below the anconeus minor and insertion of the ulnaris externus; next, to the interosseous ligament under the supinator brevis; and, lastly, to the middle part of the outside of the radius.

From thence it runs down and passes anteriorly over the lower part of the radius, and tendons of the supinator longus and radialis externus, and being gradually di-

vided, it terminates in two long flat tendons, more or less subdivided, which pass together under a particular annular ligament, being only parted by septa or frenæ belonging to that ligament.

The first of these two principal tendons is inserted in the edge of the basis of the first phalanx, near the large transverse ligament of the carpus. When this tendon is subdivided, the other portion of it is fixed in that bone of the carpus which sustains the thumb. The other principal tendon, which often belongs to a muscle entirely distinct from the former, is fixed in the convex side of the basis of the second phalanx, where it joins the tendon of the extensor secundus.

The extensor secundus is shorter than the first. It is fixed to the ulna, below the former, and above the insertion of the extensor indicis proprius, and likewise to the neighbouring part of the interosseous ligament. From thence it runs down obliquely on the middle part of the radius, where it has likewise a small adhesion. Afterwards it passes through the small channel in the styloid apophysis of the radius, through the annular ligament belonging to the tendons of the radialis externus, and over these tendons, being parted from them by a small ligamentary septum. It is inserted in the convex part of the third phalanx, near its basis.

THENAR.

THIS is a very thick fleshy muscle, in some measure pyriform, lying on the first phalanx of the thumb toward the palm of the hand, the large eminence in which is chiefly formed by it.

It is fixed to the bone which supports the thumb, and to the neighbouring part of the great internal annular ligament of the carpus. It is in some measure bicipital, two distinct portions answering to the two insertions already mentioned. As it runs along the first phalanx, these two portions unite, and, diminishing in thickness, are both inserted by one tendon in the lateral internal part of the head of the first phalanx, in the lateral part of the basis of the second, and in the lateral ligament of that joint.

MESOTHENAR.

THIS is a flat, and nearly triangular muscle, lying between the first phalanx of the thumb, and the bottom of the palm of the hand.

It is inserted, by a very broad basis, in the ligament which connects the os magnum of the carpus to that which supports the thumb. It is likewise inserted along the internal or angular part of that bone of the metacarpus, which supports the middle finger, and in the small extremity of that which answers to the index.

From thence the fibres contracting to an angle, terminate in a flat tendon of different breadths, which is inserted in that side of the head of the first phalanx of the thumb which is turned to the hollow of the hand, and in the neighbouring part of the basis of the second phalanx, by means of the second sesamoid bone belonging to that joint.

THIS is a small, flat, fleshy muscle, situated obliquely between the first phalanx of the thumb, and first bone of the metacarpus.

It is fixed by one end toward the basis of the first metacarpal bone, near the first bone of the second row of the carpus. From thence it runs obliquely toward the head of the first phalanx of the thumb, and is inserted in the lateral external part of that bone, or on that side which is turned to the first metacarpal bone. It crosses over the semi-interosseus indicis, this muscle lying toward the back of the hand, and the antithenar toward the palm.

THIS is a muscle of a considerable volume, lying along the inside of the fore-arm, fleshy for the greatest part near the articulation of the fore-arm with the os humeri, and near the carpus, terminating in four distinct portions, which become the same number of long small tendons. The name of sublimis has been given to it, because it lies almost on the surface of the fore-arm; and that of perforatus, from the slits found near the extremities of its tendons.

It is commonly made up of four muscles, closely united by their fleshy portions. It is fixed above to the superior internal parts of the ulna and radius, and to that of the interosseus ligament. A little below the middle of the fore-arm, this large fleshy body is divided into four distinct muscles, which, on the lowest quarter of the fore-arm, end in four flat tendons of different sizes.

These four tendons are inclosed in a common membranous or mucilaginous vagina, which likewise furnishes each tendon with a particular thin vagina. In this manner they advance to the carpus, and pass under the large annular transverse ligament. Beyond this ligament, they spread again in the palm of the hand, still retaining their particular vaginae, and run between the aponeurosis palmaris and metacarpus, toward the fingers, separating more and more by degrees.

Having reached the heads of the metacarpal bones, they pass under the four arches or frena formed by the furca of the aponeurosis palmaris, and particular septa of the great transverse ligament of the palm of the hand; and then each tendon having got beyond the head of one metacarpal bone, and beyond the basis of the first phalanx, enters the ligamentary vagina on the flat or inner side of that phalanx, and is inserted in the flat side of the second phalanx, near its basis, the membranous vagina accompanying it to its insertion.

In passing along the inside of the first phalanx, the tendon is divided by a long slit, which gives passage to a tendon of the perforans; and from thence the names of these two muscles are taken.

THIS muscle is very like the former, and is situated much in the same manner; only it lies lower, and is co-

vered by the perforatus. It is composed of four muscles, which at first seem to make but one mass, and afterwards terminate in four tendons.

The fleshy portions of the first and largest, and also of the second, are fixed in the superior parts of the ulna and interosseus ligament, down to their middle; the fleshy portion of the third is joined to the tendon of the ulnaris internus, by a sort of common aponeurosis; and that of the fourth is fixed along the ulna.

The four tendons have often several small collateral tendons, sometimes five in number, united to the tendons of the neighbouring muscle, as they pass under the large annular ligament of the carpus; but the tendons themselves are separated from the others by thin septa, which form a kind of particular rings. Being thus strengthened, they separate; and running along the palm of the hand in distinct membranous vaginae, like those of the perforatus, by which they are covered, they enter the ligamentary vaginae of the first phalanges together with the former; and having passed through the fissures thereof, and through the ligamentary vaginae of the second phalanges, they are inserted in the flat inner side of the third, near their basis.

THIS is a compound muscle, very much resembling the perforatus and perforans, lying on the outside of the fore-arm, between the ulnaris externus and radialis externus.

It is fixed above, by a tendinous extremity, to the posterior and lower part of the external or great condyle of the os humeri, and, by a tendinous adhesion on each side, to the ulnaris and radialis externus. It has likewise sometimes a small insertion in the radius. It is divided into four muscles, like the perforatus and perforans, and four long, slender, small tendons.

Three of these tendons pass through the common external annular ligament of the carpus; and the fourth, which goes to the little finger, passes through a particular ring of the same ligament.

Afterwards these four tendons separate as they go to the fingers, and in their passage communicate with each other, by oblique tendinous series, chiefly near the heads of the metacarpal bones.

Each tendon having reached the basis of the first phalanx, is slightly inserted therein by some lateral expansions fixed in each side of the basis. From thence it advances to the head of the same phalanx, where it is divided into two flat portions, which, at the articulation of the first phalanx with the second, leave some distance between them. About the head of the second phalanx, they unite again, and are fixed in the convex side of the third phalanx, near its basis.

THIS is a small long muscle, with a long slender tendon, lying a little obliquely on the lower and outer half of the fore-arm, between the ulna and fore-finger.

It is fixed, by its fleshy body, a little higher than the lowest

lowest third part of the outside of the ulna, below the insertion of the extensor pollicis, and it has likewise a small adhesion to the interosseus ligament. From thence it runs down, ending in a distinct tendon, without any communications, which having passed through the annular ligament of the extensor communis, afterwards joins that tendon which goes to the index.

EXTENSOR MINIMI DIGITI PROPRIUS.

THIS is a kind of collateral or auxiliary muscle of the extensor communis, of which it appears almost always to be more or less a portion.

It is fixed along the superior external half of the ulna, from whence its long small tendon runs down in company with the fourth tendon of the extensor communis, all the way to the little finger, where it joins it, and is inserted with it.

LUMBRICALES.

THESE are four very small slender muscles, lying in the hollow of the hand, in the same direction with the perforatus and perforans.

They are fixed, by their fleshy bodies, to the tendons of the perforatus on the side next the thumb, near the large annular ligament of the carpus. Near the heads of the metacarpal bones, they become very thin tendons, which accompany those of the perforans through the surface of the aponeurosis palmaris. Then they pass on to the same sides of the first phalanges, and join the tendons of the extensor communis; each of them being connected with the nearest portion thereof, at the articulation of the first phalanx with the second.

INTEROSSEI.

THESE are small muscles, lying between the metacarpal bones, and filling the three interstices left between them, both exteriorly, or towards the back of the hand, and interiorly, or toward the palm of the hand. From this situation they have the name of interossei, and have been divided into external and internal. They are commonly reckoned six in number, three external, and three internal.

The first two external interossei are for the most part inserted in the middle finger. They fill the interstices between the three first metacarpal bones, and surround the middle bone all the way to the hollow of the hand. Their tendons are fixed in both sides of the first phalanx, and in both sides of the second tendon of the extensor communis.

The third external interosseus lies in the interstice between the two last metacarpal bones, and is most commonly inserted in the ring finger; its tendon being fixed in that side of the first phalanx farthest from the thumb, and in the corresponding edge of the third tendon of the extensor communis. The fleshy body of this muscle runs in between the two bones toward the hollow of the hand.

The internal interossei are more simple than the former,

and do not lie so much between the bones. The tendon of the first is inserted in the side of the first phalanx of the fore-finger, next the little finger, and in the corresponding edge of the extensor communis. The tendon of the second goes in the same manner to the side of the ring-finger next to the thumb; and the third, to the same side of the little finger.

There are therefore two external interossei for the middle finger, one for the ring finger, but none for the fore and little finger. The middle finger has no internal interosseus; but the index, ring finger, and little finger, have each of them one.

SEMI-INTEROSSEUS INDICIS.

THIS is a small, short, flat, fleshy muscle, very like the antithenar, or internal semi-interosseus of the thumb. It is situated obliquely on one side of that of the thumb, between the first phalanx thereof, and the first metacarpal bone.

It is fixed by one end to the outside of the basis of the first phalanx of the thumb, and a little to that bone of the carpus by which this phalanx is supported; and by the other end it is fixed near the head of the first phalanx of the index, on that side next the thumb.

HYPOTHENAR MINIMI DIGITI.

THIS is a small and pretty long muscle, lying on the backside of the fourth metacarpal bone opposite to the thumb, where, together with the metacarpus, or hypothenar metacarpus, it forms that large eminence over-against the thenar or that of the thumb.

It is fixed by one end in the os orbiculare of the carpus, and a little to the neighbouring part of the large annular ligament. The other end terminates by a short flatish tendon, fixed to that side of the basis of the first phalanx of the little finger which is turned from the thumb.

USES of the Muscles which move the Fingers.

THE perforatus serves to bend the second phalanges of all the fingers except the thumb; and the particular muscles, of which it is made up, may act separately, by reason of their distinct insertions in these phalanges.

They not only bend the second phalanges on the first, but also the first on the metacarpal bones, and the metacarpus and carpus on the fore-arm.

The perforans bends particularly the third phalanges in which it is inserted; and by the same motion it may likewise bend the first and second phalanges.

It may likewise be esteemed an assistant to the ulnaris and radialis interni in great efforts; and these muscles may reciprocally be looked upon as assistants to the perforatus and perforans.

The extensor digitorum communis serves to extend the four fingers, to keep them in any degree of extension, and to moderate their flexion in all the determinate degrees of action of the perforatus and perforans.

Each tendon serves to extend a whole finger, that is,

all

all the three phalanges together; and likewise each phalanx by itself, though not with the same facility.

The proper extensors of the fore and little fingers are assistants to two subaltern muscles of the extensor communis that go to these fingers, which consequently we extend separately with more ease than either of the other two. These muscles likewise serve to bring the fingers, in which they are inserted, near the other fingers.

The flexor pollicis longus serves chiefly to bend the third phalanx of the thumb, in which it is inserted by the extremity of its tendon. It likewise bends the second phalanx, by virtue of the ligamentary vagina, through which it passes, as through an annular ligament.

The first extensor of the thumb alone, when there are three, a portion of the first, when there are but two, serves to draw the first phalanx from the palm of the hand, or to keep it at a distance therefrom.

The second of these muscles when there are three, or the second portion of the first when there are but two, serves to extend the second phalanx on the first.

The third when there are three, or the second when there are but two, extends the third phalanx on the second.

When they act all together, they assist each other by the graduated insertions of their small subaltern tendons.

The thenar, by its insertion in the first phalanx of the thumb, serves to draw it from the first bone of the metacarpus, more or less directly, as one of its portions acts more than the other, or as they both act equally.

By the insertion of the large portion in the basis of the second phalanx, by the intervention of the sesamoid bone of the same side, it may bend this phalanx laterally on the first, and thereby bring the thumb to a greater distance from the index.

The mesothenar moves the first phalanx of the thumb towards the hollow of the hand, more or less obliquely, as it acts either alone or with the large portion of the thenar, or even with the antithenar. By its insertion in the sesamoid bone of the second phalanx, it likewise moves that phalanx on the first, and thereby assists the flexor longus.

The antithenar moves the first phalanx of the thumb toward the first bone of the metacarpus, and thereby presses the thumb laterally against the index. This motion becomes more or less oblique by the co-operation of the mesothenar.

The hypothenar minor serves to separate the little finger from the rest; which motion is commonly called abduction. It likewise keeps this finger separated in all situations, that is, in all degrees of flexion or extension.

The interossei may have two different uses, according to their different insertion, and the different situations of the fingers in which they are inserted.

In general, they assist the extensor communis by their insertions in the lateral angles of the rhomboidal fissures; for thereby they act like lateral ropes, which, together with the tendons of the extensor, serve to extend the third phalanx of each finger.

By the same lateral insertions they perform the lateral motions of the fingers, that is, they press them all close

against each other, but do not separate them all, nor move each finger in particular toward, or from, the thumb. In a general separation of all the fingers, the interossei move only the middle and ring fingers; the index and little finger being separated by other muscles. In the motions of the fingers toward the thumb, which is termed adduction, they act only on three fingers, the middle, ring, and little fingers. In the contrary motion, or abduction of the fingers, they move likewise three, viz. the index, middle, and ring fingers.

The uses of the interossei in particular, whether external or internal, may be different in different subjects, according to the variety of their insertions; and therefore in living bodies nothing can be determined about them.

According to the situation in which they have been described, the first and second external interossei perform alternately the adduction and abduction of the middle finger; the third performs the abduction of the ring-finger; that is, moves it toward the little finger.

The first internal interosseus makes the abduction of the index, or moves it toward the middle finger; the second makes the adduction of the ring-finger, by moving it likewise toward the middle finger; and the third performs the adduction of the little finger, or moves it toward the middle finger.

The use of the semi-interosseus indicis is to move the first phalanx of the index, more or less directly, toward the great edge of the metacarpus, by removing it from the middle finger. This motion is not a true adduction of the index toward the thumb.

The lumbricales, by the union of their tendons with those of the interossei, are coadjutors to these muscles, not only in the lateral motions of the four fingers, but also in bending and extending them. In the lateral motions, they co-operate according to their situation in each subject; and it is possible that the variety of their insertions answer to that of the interossei, so that the reciprocal co-operation continues still to be equal.

SECT. IX. The MUSCLES which move the Os Femoris upon the Pelvis.

PSOAS sive LUMBARIS INTERNUS.

THIS is a long thick muscle situated in the abdomen on the lumbar region, adhering to the vertebrae of the loins, from the posterior part of the os ilium to the anterior part near the thigh.

It is fixed above to the last vertebra of the back, and to all those of the loins, that is, to the lateral parts of the bodies of these vertebrae, and to the roots of their transverse apophyses. The insertions in the bodies of the vertebrae are by a kind of digitations, and are very little tendinous.

From thence the muscle runs down laterally over the os ilium, on one side of the iliac muscle, and passes under the ligamentum Fallopii, between the anterior inferior spine of the os ilium, and that eminence which from its situation may be termed ilio-pelvicina.

Before

Before it goes out of the abdomen, it unites with the iliacus, and is sometimes fixed, by a few fleshy fibres, in the outside of the eminence last mentioned. It afterwards covers the fore-side of the head of the os femoris, and is inserted in the fore-part of the little trochanter by an oblique tendon, which is folded double from behind forward.

ILIACUS.

THIS is a broad thick muscle, lying on the whole inside of the os ilium.

It is fixed by fleshy fibres to the internal labium of the crista ossis ilium, to that of the slope between the two anterior spines, to the insides of these spines, to the superior half of the inside of this bone, and to the neighbouring lateral part of the os sacrum.

All these fibres, contracting by degrees, run obliquely towards the lower part of the musculus psoas, uniting therewith, and being fixed by a kind of aponeurosis to the outside of its tendon all the way to the little trochanter. They cover the head of the os femoris, and some of the lowest are inserted in that bone a little above and behind the little trochanter, and others a little lower down.

The iliacus and psoas, thus united, pass under the ligamentum Fallopii, over the slope or channel, between the anterior inferior spine of the os ilium and eminentia ilio-pectinea, in a sort of ligamentary capsula very smooth and polished.

PECTINEUS.

THIS is a small, flat, and pretty long muscle, broad at the upper part, and narrow at the lower, situated obliquely between the os pubis and upper part of the os femoris.

It is fixed above by fleshy fibres to all the sharp ridge or crista of the os pubis, and to a small part of the oblong notch or depression on the fore-side of that crista, in which the upper extremity of this muscle is lodged.

From thence it runs down obliquely towards the little trochanter, under and a little behind which, it is inserted obliquely by a flat tendon, between the superior insertion of the vastus intermedius, and inferior insertion of the triceps secundus, with which it is united.

GLUTÆUS MAXIMUS.

THIS is a thick broad muscle, lying on the outside of the os ilium and upper part of the os femoris.

It is fixed wholly fleshy to all the lateral posterior parts of the os coccygis and os sacrum; to the ligamentum sacro-sciaticum; to the outside of the tuberosity of the os ilium; and from thence to the external labium of the crista of that bone all the way to its highest part, where this muscle mixes fibres with the glutæus medius.

It is likewise fixed to the inside of the fascia lata, at the places which answer to all the insertions already mentioned, but through a much greater space, and by a

very great number of fleshy fibres, almost in the same manner as we shall see in the external plane of the musculus temporalis. The fibres which end in this fascia become gradually shorter, as they are situated lower.

All these fibres contract in breadth in a radiated manner as they approach to the great trochanter, and afterwards form a strong, flat, pretty broad tendon, about an inch in length, which is inserted a finger's breadth or a little more below the great trochanter, in all that large longitudinal impression at the upper part of the linea aspera on the back-side of the os femoris, between the vastus externus and largest portion of the triceps.

GLUTÆUS MEDIUS.

THIS is a radiated muscle, almost in the shape of a spread fan. It is pretty thick, and almost as broad as the whole outside of the os ilium, being situated between the crista of that bone and the great trochanter, and covered anteriorly by the fascia lata, and posteriorly by the glutæus maximus.

It is fixed above by fleshy fibres to all that space on the outside of the os ilium, which lies between the external labium of the crista, and the femicircular impression which goes between the superior anterior spine, and the great posterior sinus.

It is likewise fixed in the edge of that ligament which goes between the lower part of the os sacrum and os ilium. Lastly, the inner part of it, which is covered only by the fascia lata, is inserted in the inside of that fascia in the same manner as the glutæus maximus.

From thence all the fibres contract in breadth, more or less, in a radiated manner, as they advance toward the great trochanter, and form a short thick tendon, which mixes a little anteriorly with the tendon of the glutæus minimus; and the most posterior fibres gradually join the side of the tendon of the pyriformis.

The tendon is inserted in the upper convex part of the great trochanter, from the apex of the large superior external rough surface, all the way to the anterior rough surface, encompassing in a manner all that part of the trochanter.

GLUTÆUS MINIMUS.

THIS is a small, broad, radiated muscle, situated on the outside of the os ilium, under the other two glutæi.

It is fixed above in all that portion of the outside of the os ilium, which lies between the great femicircular line, and another small one, a little above the superciliary of the cotyloid cavity or acetabulum, running between the anterior inferior spine and the great posterior sinus. It is likewise fixed in the edge of that sinus, in the spine of the ischium, and in the orbicular ligament of the joint of the hip.

From thence its fibres, contracting in breadth, form a short tendon, by which the muscle is inserted in the anterior part of the upper edge of the great trochanter, above the great external convex rough surface in which the glutæus medius is fixed.

TRICEPS.

THIS, with the two following tricipital muscles, are fleshy and flat, and of different lengths, situated between the os pubis and the whole length of the os femoris. The first and second cross each other in such a manner, as that the muscle, which is the first on the os pubis, becomes the second on the os femoris; and the second on the os pubis, is the first on the os femoris. The third muscle keeps its rank.

The triceps primus is fixed above by a short tendon to the tuberosity or spine of the os pubis, and to the neighbouring part of the symphysis, its fibres mixing a little with those of the pectineus. From thence it runs down, increasing in breadth, and is inserted by fleshy fibres interiorly in the middle portion of the linea femoris aspera.

At the lower part of this insertion, a portion of the muscle separates from the rest, and sends off a long tendon, which, together with a like tendon from the triceps tertius, is inserted in the inner condyle of the extremity of the os femoris.

THIS muscle is fixed above by fleshy fibres, below the superior insertion of the triceps primus, in all the outside of the inferior ramus of the os pubis, as low as the foramen ovale, but seldom so low as the ramus of the os ischium.

From thence it runs down, and is inserted in the upper part of the linea aspera, between the pectineus and triceps primus, mixing a little with each of these muscles.

THIS muscle is fixed above by fleshy fibres to the anterior part of all the short ramus of the ischium, and to a small part of the tuberosity of that bone.

From thence it runs down, and is inserted by fleshy fibres in the linea aspera, almost from the little trochanter, down to the middle of the os femoris. It goes lower down than the first triceps, sending off a separate portion like that of the muscle last mentioned.

These two portions join together, and form a common tendon, which, running down to the lower extremity of the os femoris, is inserted in the back part of the tuberosity of the inner condyle.

THIS is a small oblong muscle, of the figure of a flat pear or pyramid, from whence it has its name. It is situated almost transversely, between the os sacrum and ischium, being covered and hid by the first two glutei.

It is fixed to the inferior lateral part of the os sacrum, by fleshy fibres, and to the neighbouring part of the anterior or concave side of that bone, by three digitations lying between the anterior holes. It is likewise fixed by

a small insertion to the ligamentum sacro-iliacum and edge of the great sinus of the os ilium.

From thence it runs transversely towards the joint of the hip, its fibres contracting in breadth, and ends in a small tendon, which is inserted in the middle of the internal labium of the upper edge of the great trochanter, by two or three branches.

THIS is a flat muscle, almost triangular, situated in the bottom of the pelvis. It covers the foramen ovale, and almost all the inside of the os pubis and ischium.

It is fixed to the internal labium of all the anterior half of the foramen ovale, a little to the neighbouring part of the obturator ligament; and also both above and below the foramen. It is likewise fixed to the upper half of the inside of the os ischium from the upper oblique notch in the foramen ovale, to the superior part of the great posterior sinus of the os ilium.

From all this extent the fleshy fibres, contracting in breadth, run down below the spine of the ischium, where they go out of the pelvis through the posterior notch of the ischium, and afterwards unite in one large flat tendon, which crossing over that of the pyriformis, unites with it, having first received on each side some additional fleshy fibres from the two gemelli.

THESE are two small, flat, narrow muscles, situated almost transversely one above the other, between the tuberosity of the ischium and the great trochanter, immediately below the pyriformis, and parted by the tendon of the obturator internus.

The superior and smallest gemellus is fixed to the lower part of the spine of the ischium, to the superior part of the small ischiatic notch, and to a rough line, which runs across the outside of the ischium, beginning from the spine, and continued under the acetabulum, where it is bent downward.

The inferior and largest gemellus is fixed to the superior and back part of the tuberosity of the ischium, and to a rough impression which runs across the outside of the ischium from the lower extremity of the ischiatic notch, and is bent upward toward the other line, together with which it forms a sort of irregular semicircle.

Both these muscles have likewise a small insertion in the inside of the ischium, where, being united together by a particular membrane, one of them joins the upper side, and the other the lower side of the obturator internus, a little after it has passed over the notch: They inclose it as in a bag, and continue to be fixed to it by fleshy fibres all the way to its extremity.

THIS is a small flat muscle, which fills up the foramen ovale of the os innominatum exteriorly, and reaches

from thence to the great trochanter of the os femoris, behind the neck of that bone.

It is fixed by fleshy fibres to the outer anterior side of the os pubis, all the way to the foramen ovale, to the edge of that hole, next the small ramus of the ischium, and a little to the neighbouring parts of the obturator ligament.

From thence its fibres, contracting in breadth, pass on the foreside of the great ramus of the ischium, under the acetabulum, where a tendon is formed, which continues its course behind the neck of the os femoris toward the great trochanter, and is inserted between the gemelli and quadratus, in a small fossula between the apex of the great trochanter, and the basis of the collum femoris.

QUADRATUS.

THIS is a small, flat, fleshy muscle, of the figure of an oblong square, from whence it has its name. It is situated transversely between the tuberosity of the ischium and the great trochanter.

It is fixed by one extremity along that obtuse line which runs from under the acetabulum, toward the lower part of the tuberosity of the ischium. From thence it runs directly toward the great trochanter, and is inserted in almost all the lower half of the oblong eminence in that apophysis; but chiefly in the small rising or tuberosity in the middle of that eminence.

MUSCULUS FASCIE LATÆ.

THIS is a small and pretty long muscle, situated a little obliquely upward and downward on the forepart of the hip.

It is fixed above to the outside of the anterior superior spine of the os ilium, between the insertions of the gluteus medius and sartorius. From thence its fleshy fibres run down a little obliquely backward, forming a very flat body, four fingers breadth in length, and two in breadth.

This body lies between two laminae of the fascia lata, and is inserted therein by short tendinous fibres, which disappear at that place where the fascia adheres to the great trochanter and tendon of the gluteus maximus.

USES of the Muscles which move the Os Femoris on the Pelvis.

THE gluteus maximus serves chiefly, by its posterior portion, to extend the os femoris, and to draw it backward. By its anterior portion, it may co-operate with the rest in performing the abduction of the thigh; but when we sit, it can do this office only by its posterior portion.

By its insertion in the os coccygis, it may on some occasions bring it forward, and hinder it from being thrust too far backward, as in the excretion of hardened faeces, or in difficult births.

The gluteus medius is commonly, but falsely, reckoned an extensor of the thigh. Its use is to separate one

thigh from the other, when we stand, and that more or less directly according to the action of its anterior, posterior, or middle portions.

When we sit, the only use of this muscle is to perform the rotation of the os femoris about its axis, in such a manner, that if the leg be bent at the same time, it shall be separated from the other.

The gluteus minimus has likewise been reckoned an extensor of the thigh, but without any foundation. It assists the gluteus medius in the abduction of the thigh when we stand, and in the rotation when we sit.

The psoas bends the thigh on the pelvis, or brings it forward. It may likewise move the pelvis on the thighs, and hinder it from being carried along with the rest of the trunk, when the body is inclined backward while we sit, having the lower extremities fixed by some external force. In this situation it may likewise move the vertebrae of the loins.

The iliacus is a congener or assistant to the psoas, in bringing the thigh forward and upward. It may likewise move the pelvis in the same manner with the former.

The pectineus is an assistant to the two former muscles in moving both the thigh and the pelvis. It may likewise assist in bringing the thigh inward, or toward the other, whether it be extended or bent at the same time.

The three triceps muscles join in the same use; that is, to move the thigh inward, and bring the two thighs near each other; as when, in riding, we press the thighs close against the saddle; when, in sitting, we hold any thing close between the knees; when we cross the thighs; or when, in standing, we bring the legs close together, in order to jump.

The use of these muscles is likewise to hinder the thighs from separating more than is convenient, especially in great efforts and jerks.

The pyriformis, gemelli, and quadratus, called likewise by the common name of quadrigemini, are congeners in their uses; and these have been confined by anatomists to the rotation of the os femoris about its axis from before outward, when we stand or lie at full length; likewise in sitting, or when the thigh is bent in any other posture, they carry the thigh outward, or separate the two thighs from each other when bent.

All the four co-operate in these two uses of rotation and abduction; but they co-operate equally or unequally, according to the different degrees of the extension or flexion of the thigh.

The obturator internus has nearly the same uses with the quadrigemini, in making the rotation of the thigh when extended, and the abduction when bent.

The obturator externus concurs with the internus in the same uses, though in a more simple manner, and in a more uniform direction. It acts chiefly when the thigh is extended more or less.

The musculus fasciæ latæ makes a rotation from before inwards, that is, in a contrary direction to that made by the quadrigemini and obturator internus; and this rotation is not so much confined as that of the quadrigemini, because it may have place whether the thigh be bent or extended.

SECT. X. The MUSCLES which move the Bones of the Leg on the Os Femoris.

RECTUS ANTERIOR sive GRACILIS ANTERIOR.

THIS muscle is as long as the os femoris; and lies directly along the foreside of the thigh, from whence it has the name of rectus anterior.

It terminates above, by a pretty strong tendon, which is divided into two branches, one short and straight, the other long and bent. The short branch, running up in a straight line, is inserted in the anterior inferior spine of the os ilium.

The long branch is inflected backward over the supercilium of the acetabulum, and runs in the direction thereof, from the spine toward the great ischiatic sinus. It is strong and flat, adhering very closely to the bone, and covered by the orbicular ligament and the gluteus minimus.

From thence the muscle runs down wholly fleshy, and partly penniform, some of its fibres meeting above and separating below. It is narrow at the upper extremity, and grows gradually broader toward the middle. Afterwards it contracts again in the same manner, and, at the lower extremity of the os femoris, ends in a flat broad tendon.

VASTUS EXTERNUS.

THIS is a very large fleshy muscle, almost as long as the os femoris, broad at the extremities, and thick in the middle, lying on the outside of the thigh.

Its upper insertion, being something tendinous, is in the posterior or convex rough surface of the great trochanter. It is likewise fixed by a fleshy insertion along the outside of the os femoris for above two thirds of its length downward, in the corresponding part of the linea aspera, and in the neighbouring portion of the fascia lata.

From all this extent the fleshy fibres running downward, and a little obliquely forward toward the rectus anterior, terminate insensibly in a kind of short aponeurosis, which is fixed in all the nearest edge of the tendon of the rectus, in the side of the patella, in the edge of the ligament of that bone, and in the neighbouring lateral part of the head of the tibia.

VASTUS INTERNUS.

THIS muscle is very like the former, and situated in the same manner on the inside of the os femoris.

It is fixed above by a short flat tendon, in the anterior rough surface of the great trochanter, and by fleshy fibres in that oblique line which terminates the basis of the collum femoris anteriorly, on the foreside of the insertions of the psoas and iliacus, in the whole inside of the os femoris, and in the linea aspera on one side of the insertions of the three tricipites, almost down to the internal condyle.

From all this extent the fibres run downward, and a little obliquely forward, and the body of the muscle in-

creases in the same manner as the vastus internus. It terminates below in an aponeurosis, which is fixed in the edge of the tendon of the rectus anterior, in the side of the patella, and of its tendinous ligament, and in the side of the head or upper extremity of the tibia.

CRUREUS.

THIS is a fleshy mass, covering almost all the foreside of the os femoris between the two vasti, which likewise cover the edges of this muscle on each side.

It is fixed to the foreside of the os femoris, from the anterior surface of the great trochanter down to the lowest quarter of the bone, by fleshy fibres which run down successively over each other, between the two vasti, and are partly united to these two muscles, so as not to seem to form a distinct muscle.

It is not so thick as the two vasti; and as it is covered by them on each side, a sort of fleshy channel is formed by all the three, in which the rectus is lodged, covering the forepart of the crureus.

It terminates below in a tendinous aponeurosis, which joins the backside of the tendon of the rectus anterior, and the neighbouring edges of the extremities of the two vasti. Thus, these four muscles form a common tendon, which is inserted in the places already mentioned.

SARTORIUS.

THIS is the longest muscle of the human body. It is flat, and about two fingers in breadth, situated obliquely along the inside of the thigh.

It is fixed above by a very short tendon, in the lower part of the anterior superior spine of the os ilium, before the musculus fasciæ latæ. The beginning of its body lies in the notch between the two anterior spines of that bone.

From thence it runs down obliquely over the vastus internus and other muscles that lie near it, all the way to the inside of the knee, where it terminates in a small tendon, which grows broader near its extremity, and is inserted obliquely and a little transversely in the forepart of the inside of the head of the tibia, near the spine or tuberosity of that bone, immediately above the insertion of the gracilis interior.

GRACILIS INTERIOR sive RECTUS INTERIOR.

THIS is a long thin muscle, lying in a straight line on the inside of the thigh, between the os pubis and the knee.

It is fixed in the edge of the inferior branch of the os pubis, near the symphysis, by a broad and very short tendon, on one side of the insertion of the triceps secundus, but a little lower down.

From thence the fleshy fibres contracting a little in breadth, run down to the internal condyle of the os femoris, where they terminate in a thin tendon, which afterwards degenerates into a kind of aponeurosis, and is inserted in the fore-part of the inside of the head of the tibia.

BICEPS.

THIS muscle is made up of two portions, one long, the other short, and they end in a common tendon. Both portions are fleshy and considerably thick, being situated on the back and outside of the thigh, between the buttock and ham.

The great portion is fixed above, by a strong tendon, in the posterior and lower part of the tuberosity of the ischium, under the insertion of the inferior gemellus, and close behind that of the semi-nervosus. From thence it runs down toward the lower extremity of the thigh, where it meets the other portion, and joins with it in forming a common tendon.

The small portion is fixed, by fleshy fibres, to the outside of the linea aspera, below its middle, and to the fascia lata, where it forms a septum between the triceps and vastus externus. From thence the fibres run down a little way, and then meeting the great portion, a common tendon is formed between them.

This strong tendon runs down to the outer and back-part of the knee, and is inserted in the lateral ligament of the joint, and in the head of the fibula, by two very short tendinous branches.

THIS is a long muscle, half fleshy and half tendinous, or like a nerve, from whence it has its name. It is situated a little obliquely, on the posterior and inner part of the thigh.

It is fixed above to the posterior part of the tuberosity of the ischium, immediately before, and a little more inward than the biceps. It is afterwards fixed, by fleshy fibres, to the tendon of the biceps, for about the breadth of three fingers, much in the same manner as the coracobrachialis is fixed to the biceps of the arm.

From thence it runs down fleshy toward the lower part of the inside of the thigh, having a sort of tendinous intersection in the inner part of its fleshy portion. Having reached below the middle of the thigh, it terminates in a small, long, round tendon, which runs down to the inside of the knee, behind that of the gracilis, where it expands in breadth.

It is inserted in the inside of the upper part of the tibia, about two or three fingers breadth below the tuberosity or spine, immediately under the tendon of the gracilis internus, with which it communicates.

THIS is a long thin muscle, partly tendinous, from whence it has its name, and situated on the back-side of the thigh, a little towards the inside.

It is fixed above, by a broad tendon or long aponeurosis, in the irregular, obtuse, prominent line which goes from the acetabulum to the tuberosity of the ischium, a little above the insertion of the semi-nervosus, and between those of the gemellus inferior and quadratus.

From thence it runs down fleshy in an oblique direction behind the inner condyle of the os femoris, below which

it terminates in a thick tendon, which is inserted in the posterior and interior side of the inner condyle of the tibia, by three short branches, the first or uppermost of which goes a little toward the inside, the second more backward, and the third lower down.

THIS is a small muscle, obliquely pyramidal, situated under the ham.

It is fixed above, by a strong narrow tendon, to the outer edge of the inner condyle of the os femoris, and to the neighbouring posterior ligament of the joint. From thence it runs obliquely downward under the inner condyle of the os femoris; it is a flat and pretty thick fleshy body, increasing gradually in breadth, till it is fixed in the back-side of the head of the tibia, all the way to the oblique line or impression observable on that side.

THE two vasti and crureus ought to be looked upon as a true triceps, the uses of which, in relation to the bones, are only to extend the tibia on the os femoris, and the os femoris on the tibia. The extension of the tibia on the os femoris happens chiefly when we sit or lie, and that of the os femoris on the tibia when we stand or walk. All the three muscles move the patella uniformly in the direction of the os femoris, on the pulley at the lower extremity of that bone.

The insertion of both the vasti immediately in the head of the tibia, prevents the patella from being luxated laterally on some occasions, in which the muscles may act with more force on one side than on the other, or remain without action, in which case the patella is loose and floating.

The rectus anterior, by its insertion in the patella, is a congener to the last three muscles, and serves to extend the leg. By its insertion in the os ilium, it bends the thigh, and assists the psoas, iliacus, and pectineus, whether the leg be extended or bent. It likewise moves the pelvis forward on the os femoris, and hinders it from falling back when we sit.

The sartorius performs the rotation of the thigh from before outward, whether extended or bent; being an antagonist to the musculus fasciæ latæ, and a congener to the quadrigemini.

It likewise bends the thigh, or raises it forward; it moves the pelvis forward on the femoris; and when the pelvis rests on the two tuberosities of the ischium in sitting, it keeps it in that situation.

Lastly, it bends the leg, whether it performs the rotation of the thigh at the same time or not.

The gracilis internus bends the leg much in the same manner with the sartorius, which it assists in this function, but not in that of turning the leg.

It may likewise assist the triceps in the adduction of the thigh, which it performs with much more facility than it begins the flexion of the leg without the rotation of the thigh.

The femi-nervosus bends the leg, and may likewise bend the thigh on the leg. By its insertion in the tuberosity of the ischium, it likewise extends the thigh on the pelvis, and carries it backward; and may also extend the pelvis on the thigh, when it has been inclined forward with the rest of the trunk; and consequently prevent its being carried too far along with the trunk, when we stoop forward, either standing or sitting.

The femi-membranosus has the same uses with the femi-nervosus. It bends the leg on the thigh, and the thigh on the leg; it extends the thigh on the pelvis, and the pelvis on the thigh, and sustains the pelvis when it is inclined forward.

The two portions of the biceps bend the leg on the thigh, and the thigh on the leg. The superior portion likewise extends the thigh on the pelvis, and the pelvis on the thigh. These four uses in general are common to this muscle with the femi-membranosus, and in some measure with the femi-tendinosus.

The particular use of the biceps, and which seems to belong more to the short portion than to the other, is to perform the rotation of the leg when bent, by which motion the toes are turned outward, and the heel inward.

The popliteus performs the rotation of the leg when bent, in a direction contrary to that of the biceps. The biceps turns the leg from before outward; the popliteus from before inward.

SECT. XI. The MUSCLES which move the Tarsus on the Leg.

TIBIALIS ANTICUS.

THIS is a long muscle, fleshy at the upper part, and tendinous at the lower, situated on the fore-side of the leg, between the tibia and the extensor digitorum longus.

It is fixed above, by fleshy fibres, in the upper third part of the external labium of the crista tibiae, and of the inside of the aponeurosis tibialis, or of that ligamentary expansion which goes between the crista tibiae and the anterior angle of the fibula. It is likewise fixed obliquely in the upper two thirds of the outside of the tibia, or that next the fibula.

From thence it runs down and ends in a tendon, which first passes through a ring of the common annular ligament, and then through another separate ring situated lower down. Afterwards the tendon is fixed, partly in the upper and inner part of the os cuboides, and partly in the inside of the first bone of the metatarsus.

PERONEUS MEDIUS vulgo PERONEUS ANTICUS.

THIS is a long muscle, situated anteriorly on the middle part of the fibula.

It is fixed above, by fleshy fibres, to more than the middle third part of the anterior or outside of the fibula, and to the neighbouring part of the aponeurosis tibialis.

It is likewise fixed to a production from the inside of that aponeurosis which runs to the upper part of the ti-

bia, and there serves for a middle septum between this muscle and the extensor digitorum longus.

From thence it runs down and forms a tendon, which going in the direction of the oblique line on the fibula, passes behind the external malleolus, and then through an annular ligament common to it and to the peroneus maximus, and is afterwards inserted in the tuberosity at the basis of the fifth metatarsal bone, sending off a small tendon to the first phalanx of the little toe.

PERONEUS MINIMUS.

THIS is a small muscle, commonly thought to be a portion of the extensor digitorum longus, though it is easily separable from it.

It is fixed, by fleshy fibres, in the lower half of the inside of the fibula, between two oblique bony lines, on one side of the lower part of the extensor digitorum longus, to which muscle it is simply contiguous.

From thence it runs down contracting in breadth, and passes with the extensor longus, through the common annular ligament, forming a flat tendon, which soon separates from those of the extensor, and is inserted near the basis of the fifth metatarsal bone.

GASTROCNEMII.

THESE are two thick, pretty broad, and oblong muscles, situated laterally with respect to each other, in the same plane, under the poples, and forming a great part of what is called the calf of the leg. That which lies next the tibia is called internus, and that next the fibula, externus; and because they form, as it were, the belly of the leg, they have been termed in Greek gastrocnemii.

Each muscle is fixed above, by a flat tendon, to the posterior part of the lower extremity of the os femoris, behind the lateral tuberosity of each condyle, adhering closely to the posterior ligaments of the joint of the knee.

From thence they run down, each forming a large and pretty broad fleshy body, irregularly oval.

About the middle of the leg, they end in a strong, broad, common tendon, which contracts a little in breadth as it descends, and is inserted in the posterior extremity of the os calcis, together with the tendon of the soleus.

SOLEUS.

THIS is a large, fleshy, flat muscle, nearly of an oval figure, and thicker in the middle than at the edges. It is situated on the back-side of the leg, lower down than the gastrocnemii, by which it is covered; and these three muscles form the calf of the leg.

It is fixed above, partly to the tibia, and partly to the fibula.

Afterwards leaving these two bones, it ends in a broad strong tendon, which, together with that of the gastrocnemii, forms what is called tend. Achillis. This strong tendon contracts a little in its passage to the os calcis, and then expanding a little, it is inserted obliquely in the back-side of that bone, all the way to the tuberosity.

THIS is a small pyriform muscle, situated obliquely in the ham below the external condyle of the os femoris, between the popliteus and gastrocnemius externus; and its tendon, which is long, flat, and very small, runs down on the side of the gastrocnemius internus, all the way to the heel.

The fleshy body, which is only about two inches in length, and one in breadth, is fixed, by a short flat tendon, above the outer edge of the exterior condyle of the os femoris, on one side of the gastrocnemius externus. From thence the fleshy body runs obliquely over the edge of the popliteus, and terminates in a very small, long, flat tendon.

This tendon runs between the body of the gastrocnemius externus and soleus, all the way to the inner edge of the upper part of the tendo Achillis; and from thence continuing its course downward, it joins this tendon, and is inserted, together with it, in the outside of the posterior part of the os calcis, without communicating with the aponeurosis plantaris.

THIS is a long, fleshy, penniform muscle, broader above than below, situated between the tibia and fibula, on the back-side of the leg, and covered by the extensor digitorum longus.

It is fixed above, by fleshy fibres, immediately under the articulation of the tibia and fibula, to the nearest parts of these two bones, chiefly to the tibia, reaching to the lateral parts of that bone, above the interosseous ligament, which is here wanting.

From thence its insertion is extended below the oblique line or impression in the tibia, over all the neighbouring part of the interosseous ligament, and through more than the upper half of the internal angle of the fibula.

After this, it forms a tendon, which runs down behind the inner malleolus, through a cartilaginous groove and an annular ligament, and, passing under the malleolus, is inserted in the tuberosity or lower part of the os scaphoides.

THIS is a long penniform muscle, lying on the fibula. It is fixed above to the anterior and outer part of the head of the fibula, and to a small portion of the head of the tibia; then to the outside of the neck of the fibula, to the upper half of the external angle of that bone, and to the aponeurosis tibialis, which at that place makes a septum between this muscle and the extensor pollicis.

From thence turning a little backward, according to the direction of the bone, it forms a considerable tendon, which, running behind the external malleolus, passes through a kind of hollow groove, and through an annular ligament common to it and to the tendon of the peroneus medius, which lies before it.

Afterwards running through the oblique groove in the lower side of the os cuboides, it is inserted in the side of

the basis of the first metatarsal bone, and also a little in the basis of the os cuneiforme majus.

THIS is a thin single muscle, lying between the tibialis anticus and extensor digitorum longus, by which it is almost hid.

It is fixed to the inside of the fibula, near the interosseous ligament, from the neck down to the lowest quarter of that bone; to the interosseous ligament through the same space, and a little to the lower extremity of the tibia next the fibula.

There it ends in a considerable tendon, which passing through a distinct ring of the common annular ligament, and then through a membranous vagina, is inserted in the basis of the first phalanx of the great toe, and continued from thence up to the second.

THIS is a pretty long muscle, situated in the posterior and lower part of the leg.

It is fixed in the lower half of the back-side of the fibula, its insertion reaching almost as far as the external malleolus. The fleshy body advances on the inside of that bone towards the tibia, according to the oblique direction of that side, and ends in a large tendon.

This tendon passes behind the lower extremity of the tibia, toward the inner ankle, then through a small notch in the inner and back-side of the astragalus, and through an annular ligament or ligamentary vagina, continued under the lateral arch of the os calcis.

From thence it advances to the great toe, and passing through the interspace between the two sesamoid bones, in the ligamentary vagina of the first phalanx, is inserted in the lower part of the second.

THIS muscle is made up of several portions, and lies on the inner edge of the sole of the foot.

It is fixed, by three or four fleshy fasciculi, to the lower and inner part of the os calcis, os scaphoides, and os cuneiforme majus. It is likewise fixed a little in the annular ligament under the inner ankle, which belongs to the tendon of the flexor longus.

From all these different insertions, the fleshy fasciculi approach each other as they advance forward under the first bone of the metatarsus, and are fixed, partly in the internal sesamoid bone, and partly in the inside of the first phalanx, near its basis.

THIS is a small compound muscle, lying obliquely under the metatarsal bones.

It is fixed posteriorly in the lower parts of the second, third, and fourth metatarsal bones, near their basis; in the ligament belonging to the first and second of these bones; in the neighbouring ligaments belonging to the bones of the tarsus; and, lastly, in a lateral aponeurosis of the muscle commonly called hypotenar.

All these portions, contracting into a small compass, are inserted in the outside of the external sesamoid bone, and of the first phalanx of the great toe.

EXTENSOR DIGITORUM LONGUS.

THIS is a long muscle, fleshy in the upper part, and tendinous in the lower, lying between the tibialis anticus and peroneus maximus.

It is fixed above, by fleshy fibres, in the outside of the head of the tibia, and inside of the head of the fibula; in the upper part of the interosseous ligament, through three fourths of the length of the fibula; and through the same space, in the tendinous septum belonging to the anterior angle of that bone.

It contracts in breadth a little above the annular ligament, and, in passing through it, is divided into three tendons; the first of which is afterwards divided into two. These four tendons are inserted along the upper or convex side of the four small toes.

EXTENSOR DIGITORUM BREVIS.

THIS is a small complex muscle, lying obliquely on the convex side of the foot, being likewise termed pedeus.

It is fixed in the upper and outer side of the anterior apophysis of the astragalus, and in the neighbouring part of the upper side of that bone. From thence it runs obliquely from without inwards, under the tendons of the peroneus minimus and extensor digitorum longus, being divided into four fleshy portions, which terminate in the same number of tendons.

The first tendon is inserted in the upper or convex part of the first phalanx of the great toe. The other three joining with those of the extensor longus, are inserted along the convex sides of all the phalanges of the three following toes.

FLEXOR DIGITORUM BREVIS
sive PERFORATUS PEDIS.

THIS is the undermost of all the common muscles of the toes, being situated immediately above the aponeurosis plantaris.

It is fixed by fleshy fibres to the anterior and lower part of the great tuberosity of the os calcis; and to the neighbouring part of the upper side of the aponeurosis plantaris.

From thence it runs forward, being divided into four fleshy portions, which terminate in the same number of tendons, split at their extremities, in the same manner as those of the sublimis or perforatus of the hand, and inserted in the second phalanges of the four small toes.

FLEXOR DIGITORUM LONGUS
sive PERFORANS PEDIS.

THIS is a long muscle, fleshy above, and tendinous below, lying on the backside of the leg between the tibia and the flexor pollicis longus, covered by the soleus, and covering the tibialis posticus.

It is fixed above, by fleshy fibres, to a little more than the middle third part of the backside of the tibia near its external angle, below the insertion of the soleus; and also to a kind of ligament which runs down from the middle of the tibia. It afterwards ends in a tendon which passes behind the inner ankle, on one side, and a little behind the tibialis posticus, in a separate annular ligament.

From thence it runs under the sole of the foot, sending off a detachment, by which it communicates with the flexor pollicis longus. There it is divided into four small flat tendons, which go to the third phalanges of the four small toes in the same manner, as the perforans of the hand.

FLEXOR DIGITORUM ACCESSORIUS.

THIS is a flat and pretty long fleshy mass, situated obliquely under the sole of the foot.

THIS muscle is fixed posteriorly by one fleshy portion, in the lower side of the os calcis, and in the anterior tuberosity on that side, and by the other in the neighbouring ligament which joins this bone to the astragalus.

From thence the two portions run obliquely to the middle of the sole of the foot, and there unite in a flat, long, and irregularly square muscular mass, which is fixed to the outer edge of the fasciculus of tendons of the flexor longus, to which it serves as a frenum at that place.

LUMBRICALES.

THESE are four small muscles, situated more or less longitudinally under the sole of the foot.

They are fixed by their fleshy extremities to the four tendons of the flexor digitorum longus near the insertion of the flexor accessorius. The first muscle is fixed to the inside of the first tendon; the second to the tendinous fork formed by the two first tendons; the third, to the tendinous fork made by the second and third tendons; and the fourth, in the same manner to the third and fourth tendons, but commonly most to the third.

From thence these four muscles run to the toes, and there terminate in the same number of small tendons, which are inserted in the first phalanges of the toes, much after the same manner as in the hand.

TRANSVERSALIS DIGITORUM.

THIS is a small muscle, which lies transversely under the basis of the first phalanges, and which at first sight appears to be a simple muscular body fixed by one end to the great toe, and by the other to the little toe.

When

When this muscle is carefully examined, we find that it is fixed, by a very short common tendon, to the outside of the basis of the first phalanx of the great toe, conjointly with the antithenar; and, by three different portions or digitations, to the three interosseous ligaments which connect the heads of the four metatarsal bones next the great toe, laterally to each other.

INTEROSSEI.

THESE are seven small muscles which fill up the four interstices between the metatarsal bones, much after the same manner as in the hand. The four largest are superior, the other three inferior.

METATARSII.

THIS is a fleshy mass, lying under the sole of the foot. It is fixed, by one end, in the fore-part of the great tuberosity of the os calcis; and running forward from thence, it terminates in a kind of short tendon, which is fixed in the tuberosity and posterior part of the lower side of the fifth bone of the metatarsus.

PARATHENAR MAJOR.

THIS is a pretty long muscle, forming part of the outer edge of the sole of the foot.

It is fixed backwards by a fleshy body, to the outer part of the lower side of the os calcis, from the small posterior or external tuberosity, all the way to the anterior tuberosity. There it joins the metatarsus, and at the basis of the fifth metatarsal bone separates from it again, and forms a tendon, which is inserted in the outside of the first phalanx of the little toe, near its basis, and near the insertion of the parathenar minor.

PARATHENAR MINOR.

THIS is a fleshy muscle, fixed along the posterior half of the outer and lower side of the fifth bone of the metatarsus. It terminates under the head of that bone, in a tendon which is inserted in the lower part of the basis of the first phalanx of the little toe.

USES of the Muscles which move the Tarsus and the other Bones of the Foot.

THE tibialis anticus bends the foot, that is, turns the point of the foot toward the leg; which motion is performed by the ginglymoid articulation of the astragalus with the tibia and fibula. It likewise bends the leg on the foot, or hinders its extension.

By its lateral insertion in the os cuneiforme maximum, it moves this bone in particular over the anterior extremity of the os calcis; by which the sole of the foot is turned inward toward the other.

The peroneus medius bends the foot, and hinders the leg from falling back in the same manner as the tibialis anticus. By its insertion in the tuberosity of the fifth metatarsal bone, it turns the sole of the foot outward at

the same time that it bends it, when it acts without the assistance of the tibialis anticus.

The peroneus minimus is an assistant to the medius in the flexion of the foot, in preserving the equilibrium of the leg, and in turning the sole of the foot outward.

THE gastrocnemii and soleus make a kind of triceps; and, by their common tendon, extend the foot, and keep it extended against the strongest resistance. It is by their means that we raise the whole body, even with an additional burden, when we stand a tip-toes; and that we walk, run and jump.

The gastrocnemii, by their insertion in the os femoris, may, in great efforts, move the leg on the thigh, and the thigh on the leg, as assistants to the biceps, femimembranosus, semi-tendinosus, gracilis internus, and sartorius.

The soleus, by the multitude of its fleshy fibres and its penniform structure, is more proper for strong than large motions, and seems principally to sustain the gastrocnemii in the motions begun by them. The tendinous portions of this muscle and of the gastrocnemii, tho' they form a strong tendon all together, seem nevertheless to slide a little upon each other in the different flexions and extensions of the foot.

Anatomists are not agreed with regard to the use of the tibialis gracilis.

When the tibialis posticus acts alone, it extends the foot obliquely inward. When it acts together with the gastrocnemii and soleus, it changes the straight direction of their motion to an oblique one. When it acts with the tibialis anticus, the sole of the foot is turned more directly inward, or toward the other foot.

When the peroneus longus or maximus acts alone, it may extend the foot hanging freely in the air; but then this extension is obliquely outward. Together with the gastrocnemii and soleus, it likewise changes their direction to an oblique extension outward.

The extensor pollicis longus extends the two phalanges of the great toe; and it may likewise be an assistant to the tibialis anticus.

The flexor pollicis longus not only bends the second phalanx of the great toe, but may likewise serve, in great efforts, as an assistant to the extensors of the tarsus. This muscle is of great use in climbing up a steep place.

The thenar bends the first phalanx of the great toe. When the portion nearest the inner edge of the foot either acts alone, or acts more than the rest, the great toe is separated from the other toes, especially if it be at the same time extended.

The antithenar, acting with the thenar, bends the first phalanx of the great toe. When it acts alone, especially if the great toe is bent, it brings it nearer the other toes, in proportion to the degrees of action of its different portions.

The two extensores digitorum communes concur in extending the four small toes; and, as the extensor longus is not near so fleshy as that of the hand, this difference is made up by the extensor brevis. The longus alone seems to extend the first phalanges; and they both join in the extension of the second and third phalanges; the brevis, by the obliquity of its direction, moderating the action

action of the longus, which otherwise would have turned the toes obliquely the contrary way.

The perforatus or flexor digitorum brevis, bends the second phalanges; and the perforans or flexor longus, the third; the use of these muscles being nearly the same with those of the perforatus and perforans of the hand.

The flexor accessorius is an assistant to the perforans, increasing its force on some occasions. It likewise directs the tendon of that muscle; for by contracting, at the same time that the fleshy belly of the perforans is in action, it makes the tendons go in a straighter line to the toes than they would otherwise do, because of their obliquity.

The lumbricales have nearly the same functions in the foot as in the hand; and they are partly assisted, and partly directed, by the flexor accessorius.

The interossei of the foot have the same uses as in the hand. The first superior muscle brings the second toe near the great toe; the other three bring the second, third, and fourth toes near the little toe. The three inferior muscles move the last three toes toward the other two.

The metatarsus moves the last bone of the metatarsus, much in the same manner as the metacarpus does that of the metacarpus.

The transversalis may assist the metatarsus in this action, which is supposed to be of use to tilers in climbing. The antithenar may likewise concur, and the peroneus minimus may serve to counterbalance these muscles, and to bring the metatarsus back to its natural situation.

The parathenar major serves particularly to separate the little toe from the rest; and the parathenar minor bends the first phalanx of that toe.

SECT. XIII. The MUSCLES employed in Respiration.

DIAPHRAGMA.

THIS is a very broad and thin muscle, situated at the basis of the thorax, and serving as a transverse partition to separate that cavity from the abdomen. For this reason the Greeks termed it diaphragma; and the Latins, septum transversum. It forms an oblique inclined arch, the fore-part of which is highest, and the posterior part lowest, making a very acute angle with the back.

It is looked upon as a double and digastric muscle, made up of two different portions, one large and superior, called the great muscle of the diaphragm; the other small and inferior, appearing like an appendix to the other, called the small or inferior muscle of the diaphragm.

The great or principal muscle is fleshy in its circumference, and tendinous and aponeurotic in the middle, which, for that reason, is commonly called centrum nervorum five tendinosum.

The fleshy circumference is radiated, the fibres of which it is made up being fixed by one extremity to the

edge of the middle aponeurosis, and by the other to all the basis of the cavity of the thorax, being inserted by digitations in the lower parts of the appendix of the sternum, of the lowest true ribs, of all the false ribs, and in the neighbouring vertebrae.

We have therefore three kinds of insertions; one sternal; twelve costal, six on each side; and two vertebral, one on each side. These last are very small, and sometimes scarcely perceivable. The costal insertions join those of the transversalis abdominis, but do not mix with them, as they seem to do before the membrane which covers them is removed.

The fibres inserted in the appendix ensiformis, run from behind directly forward, and form a small parallel plane.

The first costal insertion runs a little obliquely towards the cartilage of the seventh true rib, a triangular space being left between this and the sternal insertion, at which the pleura and peritoneum meet. The insertion of these fibres is very broad, taking up about two thirds of the cartilage of the seventh rib, and a small part of the bone, from whence it reaches beyond the angle of the cartilage.

The second insertion is into the whole cartilage of the first false rib; the third partly in the bone, and partly in the cartilage of the second false rib; the fourth in the bone, and sometimes a little in the cartilage of the third false rib; the fifth in the bone, and a little in the cartilage of the fourth false rib, being broader than the rest.

The sixth is in the cartilage of the last false rib, and almost through the whole length of the bone. At the head of this rib, it joins the vertebral insertion, which runs from the lateral part of the last vertebra of the back, to the first vertebra of the loins.

The small muscle of the diaphragm is thicker than the other, but of much less extent. It is situated along the foreside of the bodies of the last vertebra of the back and several of those of the loins, being turned a little to the left hand. It is of an oblong form, representing in some measure a fleshy collar, the two lateral portions of which cross each other, and afterward become tendinous toward the lower part.

The upper part of the body of this muscle is fixed in the slope of the middle aponeurosis of the great muscle. The outer edges of the alæ or lateral portions join the posterior plane of the great muscle, and these portions adhere to the body of the last vertebra of the back. The extremities, called likewise pillars or crura, are inserted by several tendinous digitations in the vertebrae of the loins.

The upper part of the fleshy body is formed by a particular intertexture of fibres belonging to the two alæ. These two alæ, whereof that toward the right-hand is generally the most considerable, part from each other, and form an oval hole, terminated on the lower part by fibres, detached from the inside of each ala, immediately above the last vertebra of the back. These fibres decussate and cross each other, and afterwards those that come from each ala join that on the other side, so that each of the crura is a production of both alæ.

The fibres that come from the left ala, cross over those from the right ala, and this again sends a small fasciculus of fibres over those of the left ala; afterwards the two crura part from each other.

The right crus is larger and longer than the left, and is always inserted in the four upper vertebrae of the loins, and often in the fifth likewise, by the same number of digitations, which become more and more tendinous as they descend, and at length are expanded in form of an aponeurosis. This crus lies more on the middle of the bodies of the vertebrae than on the right side.

The left crus is smaller and shorter, and lies more on the sides of the vertebrae. It is fixed by digitations to the three upper vertebrae of the loins, seldom reaching lower. The lower part of it is expanded in the same manner as the other; and the two expansions sometimes meet together.

The oval opening of this inferior muscle of the diaphragm, gives passage to the extremity of the oesophagus, and the aorta lies in the interstice between the two crura. Immediately above the opening or hole, a thin fasciculus of fibres is sent off to the stomach.

In the middle aponeurosis of the great muscles, a little to the right of the anterior part of the slope, near the small muscle, is a round opening, which transmits the trunk of the lower vena cava. The border or circumference of this opening is very artfully formed by an oblique and successive intertexture of tendinous fibres, almost like the edge of a wicker basket; and is, consequently, incapable either of dilatation or contraction, by the action of the diaphragm.

We find therefore three considerable openings in the diaphragm; one round and tendinous, for the passage of the vena cava; one oval and fleshy, for the extremity of the oesophagus; and one forked, partly fleshy, and partly tendinous, for the aorta. The round opening is to the right-hand, close to the upper part of the right ala of the small muscle; the oval opening is a little to the left; so that the right ala, which is between these two holes, lies almost directly over against the middle of the body of the eleventh vertebra of the back; the tendinous part is under the oval opening, but a little more toward the middle.

SCALENI.

THESE are compound muscles, irregularly triangular.

The scalenus primus is fixed to the upper part of the outside of the first rib, by two distinct portions, called commonly branches; one anterior, the other posterior. The anterior branch is fixed to the middle portion of the rib, about an inch from the cartilage. From thence it runs obliquely upward, and is inserted in the transverse apophysis of the sixth, fifth, and sometimes of the third vertebra of the neck.

The posterior branch is fixed more backward in the first rib, an interstice of about an inch being left between it and the other branch, through which the axillary artery and brachial nerves are transmitted. From thence it runs up obliquely behind the former, and is inserted in all the transverse apophyses of the neck.

The scalenus secundus is fixed a little more backward in the external labium of the upper edge of the second rib, sometimes by two separate portions, and sometimes without any division. The anterior portion is fixed immediately under the posterior portion of the first scalenus, by a short flat tendon, united a little with the first intercostal muscle. From thence it runs up over the posterior portion of the first scalenus, communicating likewise with that muscle, and is fixed by insertions, partly tendinous and partly fleshy, in the transverse apophyses of the four first vertebrae of the neck.

The posterior portion is fixed in the second rib, more backward than the other. From thence it runs up, being divided into two portions, whereof one is inserted in the transverse apophyses of the three first vertebrae of the neck, behind the scalenus primus. The other portion runs up behind the former, and is inserted in the transverse apophyses of the two first vertebrae.

SERRATUS POSTICUS SUPERIOR.

THIS is a flat thin muscle, situated on the upper part of the back. It is fixed on one side, by a broad aponeurosis, to the lower part of the posterior cervical ligament, and to the spinal apophyses of the two last vertebrae of the neck, and two first of the back.

From thence it runs down a little obliquely forward, and is inserted, by broad fleshy digitations, in the posterior part of the second, third, fourth, and sometimes of the fifth true ribs, near their angles; but sometimes it has no insertion in the second rib.

SERRATUS POSTICUS INFERIOR.

THIS is a flat thin muscle, lying on the lower part of the back. It is fixed in the last spinal apophysis of the back, and in the three first of the loins, by a broad aponeurosis. From thence it runs up a little obliquely, and is fixed, by fleshy broad digitations, in the last four false ribs. Its insertions, in the lowest rib, is near the cartilage, and, in the other three, near their angles.

INTERCOSTALES.

THE intercostal muscles are thin, fleshy planes, lying in the interstices between the ribs, their fibres running obliquely from one rib to another. In each interstice lie two planes, an external and an internal, closely joined together, nothing but a thin, fine, cellular, membranous web coming between them.

According to this natural division, there must be forty-four intercostal muscles in the twenty-two interstices left between the twenty-four ribs; and of these there are eleven external, and eleven internal, on each side. The fibres of the external intercostals run down from behind forward, and those of the internal intercostals from before backward; so that the fibres of these two series of muscles cross each other.

The external intercostals extend commonly from the vertebrae to the extremity of the upper labium of the bony portion of each rib, and go no further. The internal

ternal begin forward near the sternum, and end backward at the angle of each rib.

SUPRA-COSTALES.

THESE muscles are irregularly triangular, and situated on the back-part of the ribs, near the vertebrae.

Each of these muscles is fixed, by one tendinous extremity, in the transverse apophysis, which lies above the articulation of each rib, and to the neighbouring ligament; the first being inserted in the transverse apophysis of the last vertebra of the neck; and the last, in that of the eleventh vertebra of the back.

From thence the fleshy fibres run down obliquely, increasing in breadth as they descend, and are inserted in the back-part of the outside of the following rib.

SUB-COSTALES.

THESE are fleshy planes, of different breadths, and very thin, situated more or less obliquely on the insides of the ribs, near the bony angles, and running in the same direction with the external intercostals.

They are fixed by both extremities in the ribs; the inferior extremity being always at a greater distance from the vertebrae than the superior, and several ribs lying between the two insertions.

STERNO-COSTALES vulgo TRIANGULARIS STERNI.

THESE are five pairs of fleshy planes, disposed more or less obliquely on each side the sternum, and on the inside of the cartilages of the second, third, fourth, fifth, and sixth true ribs.

They are inserted, by one extremity, in the edges of the inside of all the lower half of the sternum. From thence the first muscle on each side runs up obliquely, and is fixed in the cartilage of the second rib. The second runs less obliquely to its insertion in the cartilage of the third rib. The rest are inserted, in the same manner, in the cartilages of the following ribs.

This last muscle is fixed, by one extremity, in the cartilage of the sixth true rib, near the bone, and seems to pass the appendix ensiformis, immediately above the insertion of the diaphragm in that appendix, and to join the muscle on the other side.

USES of the Muscles employed in Respiration.

THE scaleni are sometimes ranked among those which serve for respiration; but they ought rather to be ranked among the muscles which move the vertebrae of the neck; because the articulation of the first rib on both sides, with the first vertebra of the back, seems to serve only for the motion of that vertebra on the rib, and not of the rib on the vertebra.

The serratus posticus superior is disposed to move upwards the three or four upper ribs next the first.

The serratus posticus inferior is still better disposed for depressing and keeping down the last three or four false ribs.

The posterior fibres of the external intercostals are

fixed, by their upper extremities, so near the articulation of the ribs with the vertebrae, that they cannot depress that rib in which they are so inserted; whereas the insertions of their lower extremities in the following rib being at a greater distance from the articulation, they may move that rib upward. And from thence it follows, that all the remaining part of each external intercostal which terminates at the bony extremity of each rib, can only serve to raise the lower rib toward the upper.

The anterior fibres of the internal intercostals are so near the articulation of the ribs with the sternum, that they cannot depress that cartilage in which each of them is inserted; whereas the inferior insertions of these fibres being at a greater distance from the articulation, they are in a condition to raise the cartilages in which they are so inserted. From whence it follows, that all the internal intercostal muscles have the same use with the external, and that they can have no other.

The supra-costales are powerful assistants to the intercostals in their common action, and are therefore very justly termed levatores costarum.

The sterno-costales depress the cartilaginous portions, and anterior extremities of the ribs, especially the superior ribs, except the first; and at the same time draw the cartilages of the inferior ribs near the sternum, by reason of the curvature. They may therefore very well be called depressores costarum, as the supra-costales are named levatores.

The sub-costales having the superior extremities of their fibres much more distant from the vertebral articulation of the ribs than the lower extremities, it follows, that they can more easily move the upper than the lower ribs, and consequently that they are assistants to the sterno-costales.

The diaphragm, together with the intercostal muscles, the ribs, sternum, and vertebrae of the back, forms the cavity of the thorax, and it divides this cavity from that of the abdomen.

Its particular use is to be the principal organ of respiration, that is, of the alternate expansion and contraction of the thorax. The other muscles already mentioned are to be considered only as assistants and directors, in order to facilitate and regulate these motions, which, in the ordinary state, are perpetual, but which may, by the action of these other muscles, be accelerated, retarded, or even be suspended for some space of time.

The diaphragm may move when the ribs are at rest, and consequently without the assistance of the muscles which move the ribs; and this motion may be sufficient to keep up the alternate dilatation and contraction of the thorax.

SECT. XIV. The MUSCLES which move the Head on the Trunk.

STERNO-MASTOIDEUS sive MASTOIDEUS ANTERIOR.

THIS is a long, narrow, pretty thick, and mostly fleshy muscle, situated obliquely between the back part

of the ear, and lower part of the throat. It is in a manner composed of two muscles, united at the upper part through their whole breadth, and separated at the lower.

It has two insertions below, both of them flat, and a little tendinous. The first is in the upper edge of the sternum, near the articulation of the clavicle; the other in the clavicle, at a small distance from the sternum.

The sternal portion passes foremost, and covers the clavicular, both forming one body or belly, which running in the same oblique direction to the apophysis mastoidæus, is inserted in the upper and back-part of that process; over which it likewise sends off a very broad aponeurosis, which covers the splenius, and is inserted in the os occipitis.

SPLENIUS sive MASTOIDÆUS POSTERIOR.

THIS is a flat, broad, oblong muscle, situated obliquely, between the back-part of the ear, and the posterior and lower part of the neck. It is partly single, and partly made up of two portions, one superior, the other inferior.

The superior portion is fixed to the extremities of the three or four lowest spinal apophyses of the neck, and of the first, or first and second, of the back.

It is likewise fixed to the edge of the inter-spinal ligaments of the other vertebrae.

From thence it runs up obliquely toward the mastoid apophysis, partly under the upper extremity of the sternomastoidæus, and is inserted in the upper part of that process, and along the neighbouring curve portion of the transverse ridge of the os occipitis.

The inferior portion of the splenius is fixed to three or four spinal apophyses of the back, beginning by the second or third. From thence it runs up, being closely united to the other portion, till it reaches the superior and lateral part of the neck, where it separates from it, and is inserted in the transverse apophyses of the three or four superior vertebrae of the neck, by the same number of extremities, a little tendinous, which, however, are sometimes only two in number.

COMPLEXUS.

THIS is a pretty long and broad muscle, lying on the posterior lateral part of the neck, all the way to the occiput. It is complicated, by reason of the decussations of its different portions; from which it has its name.

It is fixed below, by small short tendons, to the transverse apophyses of all the vertebrae of the neck, except the first, to which it is fixed only near the root of its transverse apophysis. From thence it runs up obliquely backward, crossing under the splenius, and often communicating with it, by some fasciculi of fibres.

It is afterwards inserted above, by a broad fleshy plane, in the posterior part of the superior transverse line of the os occipitis, near the crista or spine of that bone.

COMPLEXUS MINOR sive MASTOIDÆUS LATERALIS.

THIS is a long, slender, narrow indented muscle, ly-

ing along all the side of the neck, up to the ear, where it increases a little in breadth.

It is fixed, by one extremity, in all the transverse apophyses of the neck, except the first, by the same number of digitations or branches, mostly fleshy, and disposed obliquely.

From thence it ascends, and having reached above the transverse apophysis of the first vertebra, it forms a small broad plane, by which it is inserted in the posterior part of the apophysis mastoidæus.

RECTUS MAJOR.

THIS is a small, flat, short muscle, broad at the upper part, and narrow at the lower, situated obliquely between the occiput and second vertebra of the neck.

It is fixed below to one branch of the bifurcated spine of the second vertebra of the neck, at a tuberosity which is often found at the upper part of that branch. From thence it ascends a little obliquely outward, and is inserted in the posterior part of the inferior transverse line of the os occipitis, at a small distance from the crista, being a little covered by the obliquus superior.

RECTUS MINOR.

THIS muscle is like the former, and it has also a small insertion below, in the posterior eminence of the first vertebra. From thence it ascends laterally, and is inserted immediately under the posterior part of the inferior transverse line of the os occipitis, in a superficial fossula on one side of the crista occipitalis.

OBLIQUUS SUPERIOR sive MINOR.

THIS muscle is situated laterally between the occiput and first vertebra, being nearly of the same figure with the two recti. It is fixed to the end of the transverse apophysis of the first vertebra; from whence it runs upward and very obliquely backward, and is inserted in the transverse line of the os occipitis, almost at an equal distance from the crista and mastoid apophysis, between the rectus major and complexus minor.

OBLIQUUS INFERIOR sive MAJOR.

It is situated in a contrary direction to the obliquus superior, between the first and second vertebra of the neck, resembling that muscle in every thing but the size. It is fixed below to one ramus of the bifurcated spinal apophysis of the second vertebra, near the insertion of the rectus major; from whence it runs obliquely upwards and outward, and is inserted in the end of the transverse apophysis of the first vertebra, under the lower insertion of the obliquus superior.

RECTUS ANTICUS LONGUS.

THIS muscle is, in some measure, of a pyramidal figure, lying along the anterior and lateral parts of the vertebra of the neck, all the way up the basis cranii.

It

Anatomical illustration of the hand muscles, showing the intricate network of muscles and tendons. Labels include: l, k, h, g, f, e, d, c, b, a, n, i, m, o, p, q, r, s, t, u, v, w, x, y, z.

Anatomical illustration of the human back muscles, showing the intricate network of muscles and tendons. Labels include: A, B, C, D, E, F, G, H, I, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z.

Anatomical illustration of the foot muscles, showing the intricate network of muscles and tendons. Labels include: a, b, c, d, e, f, g, h.

Anatomical illustration of the gluteal muscles, showing the intricate network of muscles and tendons. Labels include: a, b, c, d, e, f, g, h.

Anatomical illustration of the pectoral muscles, showing the intricate network of muscles and tendons. Labels include: a, b, c, d, e, f, g, h.

It is fixed to the anterior parts of the transverse apophyses of the third, fourth, fifth, and sixth vertebrae in a digitated manner. From thence it runs obliquely inward toward the lateral parts of the bodies of the vertebrae, passes on the fore-side of the first and second, without being inserted in them; and, approaching gradually towards the same muscle on the other side, it is inserted near it in the fore-part of the lower side of the apophysis basilaris, or great apophysis of the os occipitis.

RECTUS ANTICUS BREVIS.

THIS is a small flat muscle, about the breadth of one finger, situated laterally on the anterior part of the body of the first vertebra. It is fixed below to the basis or root of the transverse apophysis of that vertebra, near the anterior eminence.

From thence it runs obliquely upward and inward to a transverse impression in the lower side of the apophysis basilaris of the occipital bone, immediately before the condyle on the same side, being covered by the rectus anticus longus.

TRANSVERSALIS ANTICUS PRIMUS.

THIS is a small, pretty thick, and wholly fleshy muscle, about the breadth of a finger, situated between the basis of the os occipitis and the transverse apophysis of the first vertebra. It is fixed by one end in the anterior part of that apophysis; and from thence running up a little obliquely, it is inserted, by the other end, in a particular impression, between the condyle of the os occipitis and the mastoid apophysis of the same side, behind the apophysis styloides, and under the edge of the jugular fossula.

TRANSVERSALIS ANTICUS SECUNDUS.

THIS is a small muscle, situated between the transverse apophyses of the first two vertebrae of the neck. It is fixed, by one extremity, very near the middle of the second apophysis, and, by the other, near the root or basis of the first; and therefore it is a muscle of the neck, rather than of the head.

MUSCULI ACCESSORII.

WE sometimes meet with a small muscle, fixed, by one end, to the extremity of the first transverse apophysis of the neck, near the insertions of the two obliqui, from whence, running up obliquely, it is again inserted behind the mastoid apophysis. This muscle is commonly thought to be a third small transversalis on that side where it is found, but it seems rather to be an additional muscle to the obliquus superior.

USES of the Muscles which move the Head on the Trunk.

THE action of the sterno-mastoidei is different, according as either both muscles, or only one of them, acts, Vol. I. No. 10.

and according to the different situation of the head and trunk.

When we keep the head and trunk straight, whether in standing or sitting, both muscles preserve the head in that posture against any force by which it would otherwise be moved backward.

One of these muscles acting alone, may have the same use, if the force to push the head back be applied between the anterior and lateral parts of it.

They both serve likewise to perform the rotations of the head, that is, to make it turn to either side as on a pivot; and, in this case, when we turn the head to one side, the sterno-mastoideus on the other side acts, and not that on the same side.

They both serve, in the next place, to bring the head near the thorax when we lie on the back, or bend backward in sitting. In this case, the sternum, being the fixed point, must remain immovable; but as its connection with the first rib, and the inflexibility of the cartilage of that rib, are not always sufficient for this, the musculi recti of the abdomen must lend their assistance in great efforts.

The two splenii serve to support the head in an erect posture, whether in standing or sitting; to moderate the flexion of the head forward, and to bring it back again to its natural posture.

They serve alternately to co-operate with either of the sterno-mastoidei, for the rotation of the head: Thus when the right sterno-mastoideus turns the head, the left splenius corresponds with it by its upper part; while the lower part at the same time turns the vertebrae of the neck.

The complexi are assistants to the splenii, to keep the head straight in sitting or standing, to hinder it from inclining forward, and to raise it when inclined.

The recti maiores, and minores postici, and obliqui superiores, turn the head a little backward on the first vertebra of the neck. The recti maiores contribute most to this motion; and the minores seem likewise to hinder the articular membranes from being pinched between the bones in great motions.

The recti maiores and minores antici, and the two transversales antici, move the head forward on the first vertebra; and the recti minores, and transversales breves, likewise defend the capsular ligaments.

The obliqui inferiores or maiores are true rotators of the head, by turning the first vertebra upon the odontoid apophysis of the second; all which alternate motions the head follows, without being hindered in the motions forward and backward in any degree of rotation.

Of the transversales antici, the first only move the head in the manner above mentioned; neither can they perform any other motions, their insertions being confined to the os occipitis and first vertebra. The transversales antici secundi have no share in the particular motions of the head, but ought rather to be ranked among the muscles which move the vertebrae of the neck.

The complexi minores belong to the head only by their superior portions; the other portions belonging rather to the neck. They may serve alternately in the lateral motions of the head, and thereby co-operate with the splenii.

nus and sterno-mastoideus of the same side, when these two act together; and they may likewise be of use to preserve the capsular ligaments to which they adhere.

The small accessorii, when they are found, have the same uses with the muscles to which they are supernumerary.

SECT. XV. Of the Vertebral MUSCLES.

LONGUS COLLI.

THIS vertebral muscle is made up of several others, situated laterally along the fore-side of all the vertebrae of the neck, and some of the upper vertebrae of the back.

It may be divided into two portions; one superior, consisting of oblique converging muscles; and one inferior, composed of oblique diverging muscles.

The superior portion is covered by the rectus anticus longus of the head. The muscles, of which it consists, are fixed below to all the transverse apophyses that lie between the first vertebra and the last. From thence they run up obliquely, and are inserted in the anterior eminence of the first vertebra, and in the bodies of the three following.

The inferior portion appears almost straight, and yet all the muscles that compose it are diverging, or directed obliquely outward. They are fixed below to the anterior lateral part of the body of the last vertebra of the neck, and of the first three of the back, and sometimes of more. From thence they run upward, and a little obliquely outward, and are inserted near the transverse apophyses of all the vertebrae of the neck, except the first and last.

TRANSVERSALIS COLLI MAJOR.

THIS is a long thin muscle, placed along all the transverse apophyses of the neck, and the four, five, or six upper apophyses of the back, between the complexus major and minor.

It is composed of several small muscular fasciculi, which run directly from one or more transverse apophyses, and are inserted sometimes in the apophysis nearest to these, sometimes in others more remote, the several fasciculi crossing each other between the insertions of the two complexi, which are likewise crossed by them.

TRANSVERSALIS GRACILIS five COLLATERALIS COLLI.

THIS is a long thin muscle, resembling the transversalis major in every thing but size, and situated on the side of that muscle.

SEMI-SPINALIS five TRANSVERSO-SPINALIS COLLI.

THIS name is given to all that fleshy mass which lies between the transverse and spinal apophyses, from the second vertebra of the neck, to the middle of the back.

It is composed of several oblique converging mus-

cles, which may be divided into external and internal.

The external are fixed below to the transverse apophyses of the six, seven, eight, or nine upper vertebrae of the back, by tendinous extremities, which, as they ascend, become fleshy, and mix with each other. Their superior insertions in the neck are six in number, whereof the first, which is tendinous, is in the seventh spinal apophysis; the rest, which are fleshy, are in the five next spinal apophyses.

The internal are shorter and more oblique than the external, and partly covered by them. They are fixed, by their lower extremities, to the transverse apophyses of the three or four upper vertebrae of the back, and to the oblique apophyses of the four or five lower vertebrae of the neck; and, by their other extremities, they are inserted in the six spinal apophyses of the neck.

SPINALES COLLI MINORES.

THESE muscles lie between the six spinal apophyses of the neck, and between the last of the neck and first of the back, being inserted in these apophyses, by both extremities, on one side of the posterior cervical ligament, which parts them from those on the other side.

TRANSVERSALES COLLI MINORES.

THESE are very small short muscles, found in the interstices of several transverse apophyses in which they are inserted. They are likewise termed inter-transversales.

SACRO-LUMBARIS.

THIS is a long complex muscle, narrow and thin at the upper part, broad and thick at the lower, representing a kind of flat pyramid. It lies between the spine and posterior part of all the ribs, and along the back-part of the regio lumbaris, all the way to the os sacrum.

Through all this space, it is closely accompanied by the longissimus dorsi, which lies between it and the spinal apophyses of the vertebrae, a narrow, fatty, or cellular line running between them.

It is fixed below, by a broad thin tendinous aponeurosis, to the superior spines of the os sacrum, and to the neighbouring lateral parts of that bone; and, lastly, to the external labium of the posterior part of the crista ossis ilium, all the way to the great tuberosity.

From thence this muscle runs upward, and a little laterally, over all the regio lumbaris; the aponeurosis fending off, from its inside, a mass of fleshy fibres, which are divided, from below upwards, into several large fasciculi, inserted in all the transverse apophyses of the loins.

Afterwards it runs up obliquely over all the ribs, sometimes as high as the two or three lowest vertebrae of the neck, sometimes higher, and sometimes it ends at the first vertebra of the back.

LONGISSIMUS DORSI.

THIS is a very complex, long, and narrow muscle, something

something like the sacro-lumbaris, but more fleshy and thicker, situated between the spinal apophyses and the muscle just mentioned, from which it is divided by a small, fatty, or cellular line; but at the lower part they are confounded together. It covers the semi-spinalis, or transverso-spinalis dorsi, and the semi-spinalis lumborum. Its upper part lies between the sacro-lumbaris and transversalis colli.

Its inferior insertions are partly by distinct tendinous portions, and by a broad aponeurosis common to it with the sacro-lumbaris; and partly by a large fasciculi of fleshy fibres, which, at first sight, seem to compose one uniform mass. It is fixed, by the long, flat, tendinous portions of different breadths, to the last spinal apophysis of the back, to all those of the loins, and to one or two of the superior spines of the os sacrum. These portions lie at different distances from each other, but are all connected by a thin aponeurosis fixed to their edges.

From thence they run up obliquely, diverging from the apophyses; and, beginning to be fleshy at their inner or anterior sides, they terminate above in small roundish tendons, inserted in the extremities of the seven upper transverse apophyses of the back, and in the neighbouring ligaments of all the true ribs.

The other inferior insertion wholly fleshy, is partly in the inner or foreside of the aponeurosis of the sacro-lumbaris, and partly in the upper portion of the os sacrum, being from thence continued to the great tuberosity of the os illium.

From thence this uniform mass of fleshy fibres runs up in a course almost direct, crossing the tendinous portions which are more oblique; and join the inferior fibres of the sacro-lumbaris by large fasciculi inserted in the transverse and oblique apophyses of the vertebrae of the loins. The fibres of this portion go afterwards to the ribs, being inserted by planes more or less fleshy, in the lower convex edge of all the false ribs, between the condyles or tuberosities and the angles.

At the sixth or seventh vertebra of the back, one or more of the tendinous portions often communicate with some fasciculi of the semi-spinalis, or transverso-spinalis dorsi.

SPINALIS DORSI MAJOR.

THIS is a pretty long and slender muscle, lying upon the lateral part of the extremities of the spinal apophysis of the back.

It is composed of several muscular fasciculi of different lengths, which, crossing each other, are inserted laterally by small tendons in the spinal apophyses from the second, third, or fourth vertebra of the back; and sometimes, though seldom, from the last of the neck, or first of the back, all the way to the first or second vertebra of the loins, with several irregular decussations, which vary in different subjects.

SPINALES DORSI MINORES.

THESE muscles are of two kinds. Some go laterally from the extremity of one spinal apophysis to another;

being often mixed with the short fasciculi of the spinalis major. The rest lie directly between the extremities of two neighbouring spinal apophyses, being separated from their fellows on the other side by the spinal ligament. They are smaller and thinner than those of the neck, and are properly enough termed inter-spinales.

TRANSVERSALES DORSI MINORES.

SOME particular muscles of this kind are found fixed to the extremities of the three lowest transverse apophyses of the back. The rest are all in some measure continuations of the transversalis major.

SEMI-SPINALIS sive TRANSVERSO-SPINALIS DORSI.

THIS is a fleshy mass, which, from all the spinal and transverse apophyses of the back and loins, is extended into distinct fasciculi over the vertebrae themselves.

It is made up, like that of the neck, of several oblique converging vertebral muscles, the uppermost of which is fixed below to the third transverse apophysis of the back, and above to the first spinal apophysis. The lowest is fixed below to the third transverse apophysis of the loins, and above to the last spinal apophysis of the back.

They may be divided into external, which are first discovered; and internal, which lie immediately on the vertebrae. The external, from the first vertebra to the seventh, inclusively, appear to be longer than the internal, which are covered by them.

TRANSVERSO-SPINALIS LUMBORUM,
SACER VETERIBUS.

THIS muscle is composed of several oblique converging or transverso-spinal muscles, in the same manner as in the back and neck; and it lies between the spinal and oblique apophyses of the loins, reaching to the os sacrum.

The lowest of these muscles are fixed to the superior lateral parts of the os sacrum, to the ligamentum sacro-iliacum, and to the posterior superior spine of the os illium. The rest are fixed to the three lowest transverse apophyses, and to the four lowest oblique apophyses of the loins, and to their lateral tuberosities. From thence they run up to all the spinal apophyses of these vertebrae, the external, or those that appear first, being longer than the internal, which lie immediately on the vertebrae, especially toward the lower part.

SPINALES & TRANSVERSALES LUMBORUM.

THERE are some fasciculi which run up from the superior false spines of the os sacrum, to the lower spinal apophyses of the loins, which may be looked upon as so many spinales lumborum maiores. There are likewise some spinales minores between the spinal apophyses of the loins, and transversales minores between the transverse apophyses, which are sometimes of a considerable breadth.

THIS is a small, oblong, flat muscle, irregularly square, narrower at its upper than at its lower part, lying along the sides of the vertebrae lumborum, between the last false rib and the os ilium.

It is fixed below to the external labium of almost all the posterior half of the crista ossis ilium, to the ligamentum sacro-iliacum, and a little to the os sacrum, by a fleshy plane, the fibres whereof run obliquely backward.

From thence it runs up between the sacro-lumbaris and psoas, by both which it is partly hid, and is inserted in the extremities of all the transverse apophyses of the loins by oblique tendinous digitations. It is likewise fixed by a broad insertion in the twelfth rib, on the inside of the ligament that lies between it and the longissimus dorsi, by which that rib is connected to the first vertebra of the loins.

THESE are small, thin, radiated muscles, lying on the inner or concave side of the os sacrum, and neighbouring parts of the pelvis. They are four in number, two on each side, whereof one is placed more forward, the other more backward; for which reason the first may be termed coccygeus anterior, five ischio-coccygeus; the other coccygeus posterior, five sacro-coccygeus.

The coccygeus anterior is fixed by a broad insertion in the anterior portion of the small transverse ligament, at the upper part of the foramen ovale of the os innominatum, which is no more than a particular fold of the great transverse ligament of the pelvis. From thence it runs between this great ligament and the musculus obturator internus, and, contracting in breadth, it is inserted in the lower part of the os coccygis.

The coccygeus posterior, or sacro-coccygeus, is fixed to the inner or concave edge of the two first vertebrae of the os sacrum, to the inner and lower edge of the ligamentum sacro-sciaticum, and to the spine of the os ischium. From thence, contracting in breadth, it is inserted in the inside of the os coccygis above the former muscle.

THIS is a long slender muscle, lying upon the psoas major.

It is fixed above by a short tendon, sometimes to the last transverse apophysis of the back, or higher; sometimes to the first of the loins, and sometimes to both. From thence it runs down wholly fleshy, and more or less complex, on the great psoas, in a direction a little oblique.

Having reached the middle of the regio-lumbaris, or thereabouts, it forms a slender flat tendon, which gradually increasing in breadth, like a thin aponeurosis, runs over the psoas major and iliacus internus, at their union, and from thence down to the symphysis of the os pubis and os ilium, and is inserted chiefly in the crista of the os pubis, above the insertion of the pectineus, sometimes sending an aponeurotic lamina further down.

THE scaleni, when they act on each side at the same time, may assist in bringing the neck forward, when we lean back in any respect. When those of one side act by themselves, they make a lateral inflection, either of all the vertebrae of the neck together, as in bending the middle of the neck; or of some only, as in bending the lower part of the neck alone.

The longi colli bring the neck forward by the lower part of their inferior portions. When one of them acts alone, or acts more than the other, this motion is more or less oblique.

By the upper and greatest part of the lowest portion, they counterbalance the posterior muscles of these vertebrae, and hinder the neck from bending backward by the contraction of the sterno-mastoidari, when, lying on the back, we raise the head.

The transversalis major, transversalis gracilis, and the little transversales, acting on one side, can have no other use but to bend the neck laterally, and to hinder these inflexions when they act on both sides.

The semi-spinales or transverso-spinales of both sides acting together, extend the neck upon the trunk, to keep it from inclining forward in standing or sitting, and bend it backward. The semi-spinales of one side acting alone, produce the same motions in an oblique direction; and in that case they are assisted by the inferior or vertebral portion of the neighbouring splenius, under which they cross.

The semi-spinales of both sides may likewise serve for the rotation of the neck, but then the inferior splenius of the opposite side must assist them.

The inter-spinales are assistants to the semi-spinales in their mutual action, and may likewise serve to bring back the neck to its natural situation, after small motions of rotation.

The vertebrae of the back are moved by being bent forward, by being extended or straightened, and by being inflected directly or obliquely toward each side. The motion of rotation has no place here, because of the particular structure of the joints of these vertebrae, and their connexion with the ribs, which likewise hinder the flexion backward. Flexion and extension are the two principal motions, and much more apparent than the others.

The flexion of the back forward is not performed by any particular muscles, but depends, both in standing and sitting, on the relaxation of the muscles that extend or straighten it, and keep it in that erect posture.

The two sacro-lumbaris maintain the back and the regio-lumbaris in their natural situation when we stand or sit; and by the relaxation of their fibres more or less, the trunk is proportionably bent forward by the weight of the head and breast. They likewise extend the back and loins in all postures, keep them steady and fixed under the weight of burdens, and bend the loins backward.

The longissimus dorsi is an assistant to the sacro-lumbaris, especially to the vertebral portion of that muscle, which it helps very powerfully, both by the multiplicity and insertion of its fibres, in sustaining the vertebrae of the

the back and loins while extended, whether in sitting or standing, and in preventing their sinking under the weight of the body, or of any additional burden. It assists in performing and in counterbalancing all the motions and inflexions of which these vertebrae, especially those of the loins, are capable in all postures of the body.

All the spinales and transversales of the back and loins belonging to the class of the vertebrales recti, the spinales to the middle muscles, and the transversales to the lateral, their chief uses must be to assist, moderate, and maintain the motions of extension and lateral inflexion, whether simple and direct, or oblique and compound.

The semi-spinales, or transversos-spinales, being oblique, converging, vertebral muscles, are assistants to the sacro-lumbaris and longissimus dorsi, which they cross on each side.

The quadratus lumborum and psoas parvus are of the same use to the vertebrae of the loins, as the scaleni to those of the neck. When both quadrati act, they keep the lumbar pillar straight, that is, so as not to incline to either side, and then they may assist the recti of the abdomen in the inflexions forward, and the superior portions of the obliqui in lateral inflexions.

They may likewise serve to support the haunches alternately in walking; and, in standing on one foot, the quadratus of the opposite side may support the haunch of that side.

The psoas parvus, serves to sustain the pelvis much in the same manner with the musculi recti of the abdomen, in climbing, &c.

The coccygeus anterior may sustain the coccyx in æquilibrium, and hinder it from being bent backward, and from being luxated in great strains, as in the excretion of hardened faeces, &c.

The coccygeus posterior can only serve to replace the os coccygis when it has been forced backward, and to hinder it from being luxated backward.

SECT. XVI. The MUSCLES which move the Lower Jaw.

MASSETER.

THIS is a very thick fleshy muscle, situated at the back part of the cheek. It seems to be made up of three portions, like a triceps, viz. one large and external portion, one middle, and one small and internal.

The external portion is fixed by one tendinous extremity to all the inferior edge of the os malæ, and a little to the neighbouring parts of the os maxillare and apophysis zygomatica of the os temporum. From thence it runs down obliquely backward, being wholly fleshy, and is inserted by the other extremity in the rough impression on the outside of the angle of the lower jaw.

The middle portion is fixed by one end to the lower edge of the whole apophysis zygomatica of the os temporum, and a very little to that of the os malæ. From thence it runs down a little obliquely forward in an opposite direction to the first portion, under which it crosses,

and is inserted by its other extremity in the middle of the inside of the ramus of the lower jaw, near the insertion of the external portion with which it mixes.

The third portion, which is least and most internal, is fixed by one extremity to the inner labium of the lower edge, and also to the inside of almost all the zygomatic arch; and by the other, to the root or basis of the coronoid apophysis, where it mixes wholly fleshy with the insertion of the middle portion.

TEMPORALIS.

THIS is a broad flat muscle, resembling the quadrant of a circle in figure. It occupies all the semi-circular or semi-oval plane of the lateral region of the cranium, the temporal fossa, and part of the zygomatic fossa. From this situation it has its name.

To conceive justly the insertions of this muscle, it must be observed, that the pericranium is divided into two laminae. The internal lamina, sometimes taken for a particular periosteum, covers immediately all the bony parts of this region. The external lamina separated from the other, is spread out like an aponeurotic or ligamentary tent, by means of its adhesions to the external angular apophysis of the os frontis, to the posterior edge of the superior apophysis of the os malæ, and to the upper edge of all the zygomatic arch, all the way to the root of the mastoid apophysis.

This muscle is composed of two planes of fleshy fibres, fixed to the two sides of a tendinous plane nearly of the same breadth with them, like a concealed middle tendon; as may be plainly seen by dividing the muscle all the way to the bone, according to the direction of its fibres. The body of the muscle thus formed is inclosed between the two aponeurotic or ligamentary laminae in the following manner.

The internal fleshy plane is fixed, by a broad radiated insertion, to all the semi-circular plane of the cranium, by the intervention of the internal lamina of the periosteum.

Thus it is fixed to the lateral external part of the os frontis, and to its external angular apophysis, to the lower part of the os parietale, to the squamous portion of the os temporis, to the great ala or temporal apophysis of the sphenoidal bone, by which the temporal fossa is formed; and a little to the backside of the internal orbital apophysis of the os malæ, which forms part of the zygomatic fossa.

PTERYGOIDEUS MAJOR five INTERNUS.

This muscle lies on the inside of the lower jaw, almost in the same manner as the masseter does on the outside, being of the same figure with that muscle, only smaller and narrower.

It is fixed above in the pterygoid cavity, chiefly to the inside of the external ala of the apophysis pterygoideus.

It runs down obliquely toward the angle of the lower jaw, and is inserted a little tendinous in the inequali-

ties on the inside thereof, opposite to the insertion of the masseter.

PTERYGOIDEUS MINOR five EXTERNUS.

THIS is an oblong fleshy muscle, much smaller than the other, and situated almost horizontally between the outside of the apophysis pterygoidea, and the condyloid apophysis of the lower jaw, the subject being considered in an erect posture.

It is fixed by one extremity to the outside and edge of the outer ala of the pterygoid apophysis, filling the fossula which is at the basis of this apophysis, near the basis of the temporal apophysis, of the sphenoidal bone.

From thence it runs backward, and a little outward, into the void space between the two apophyses of the lower jaw, and is inserted anteriorly in the condyloid apophysis, at a small fossula immediately under the inner angle of the condyle. It is also fixed to the capsular ligament of the joint.

DIGASTRICUS.

THIS is a small long muscle, situated laterally between the whole basis of the jaw and the throat. It is fleshy at both extremities, and tendinous in the middle, as if it consisted of two small muscles joined endwise by a tendon, and from thence it is called digastricus in Greek, and biventer in Latin.

It is fixed by one fleshy extremity in the sulcus of the mastoid apophysis. From thence it runs forward, inclining towards the os hyoides, where the first fleshy body ends in a round tendon, which is connected to the lateral part and root of the cornua of that bone by a kind of aponeurotic ligament, and not by a vagina or pulley.

Here the tendon is incurvated, and presently ends in the other fleshy body, which is fixed immediately above the internal labium of the basis of the chin near the symphysis, in a small unequal depression. This insertion is broader than that of the other extremity.

Uses of the Muscles which move the Lower Jaw.

THE two temporales acting together, raise the lower jaw, press the teeth in that jaw against the upper teeth, and pull it back when it has been carried so far forward as that the lower incisors get before the upper. They perform the last motion by their most posterior portion, which passes over the root of the zygomatic apophysis, and the other motions by the co-operation of all their muscular radii.

The two masseters serve to raise the lower jaw, and to push the lower teeth against the upper, in which use they co-operate with the temporales. They likewise bring this jaw forward by their external and largest portion; draw it back by their middle portion; and move it laterally by their superior portions acting alternately. By the co-operation of all the three portions, they press the lower teeth against the upper.

Both pterygoidei interni serve to raise the lower jaw, to bring the lower teeth near the upper, and to move the jaw laterally, as in grinding the food.

The two pterygoidei externi bring the lower jaw forward, in order to set the lower incisors before the upper; in which action they are antagonists to the posterior portion of the temporales, and the great portion of the masseters. When one of them acts, it carries the chin obliquely forward, or turns it toward the other sides. This oblique motion is performed alternately by these two muscles acting singly.

The two digastrici serve to depress the lower jaw, and to open the mouth.

The force of these muscles is very considerable, as may be shewn by laying the elbow on a table, and leaning with the chin on the hand, while we endeavour at the same time to depress the lower jaw; for as in that case this jaw cannot descend, the digastrici, by their insertions in the apophysis mastoidea, raise the upper jaw, by bending the head backward on the condyles of the lower jaw.

SECT. XVII. The Muscles which move the Os Hyoides.

MYLO-HYOIDÆUS.

THIS is a broad, thin, penniform muscle, situated transversely between the internal lateral parts of the basis of the lower jaw, and lying on the anterior portions of the two digastric muscles.

It is made up of two equal fleshy portions, one lying on the right side, the other on the left, both in the same plane, and joined to a small middle tendon, which is inserted anteriorly in the middle of the basis of the os hyoides, and from thence runs directly forward, diminishing gradually in its course.

Each portion is fixed, by fleshy fibres, to the internal lateral part of the lower jaw, between the oblique prominent line and the basis, under the first four dentes molares and caninus. The anterior and greatest part of the other fibres of each portion run obliquely from before backward, to the middle tendon, in which they are regularly fixed, the anterior fibres being the shortest, and a small triangular void space being formed between them and the symphysis of the chin.

The posterior fibres of each portion, which make about a fourth part of the whole, run likewise on each side to the basis of the os hyoides, and are inserted along the lower edge of its anterior or convex side, and from thence a little upward.

GENIO-HYOIDÆUS.

THIS is a small and pretty long fleshy muscle, situated between the symphysis of the chin and the os hyoides, close by its fellow.

It is fixed, by its anterior extremity, to a rough, and sometimes prominent surface, on the inner or posterior side of the symphysis of the lower jaw, a little above the chin. From thence it runs backward, and is inserted anteriorly in the upper edge of the basis of the os hyoides,

des, having first sent off a small lateral portion, which is fixed a little higher to the root of the cornu.

STYLO-HYOIDÆUS.

THIS is a small fleshy muscle, lying obliquely between the apophysis styloides and os hyoides.

It is fixed laterally, by one extremity, to the root or basis of the apophysis styloides, and, by the other, to the os hyoides, at the place where the basis and cornu unite, and likewise to the cornu itself, from whence it has been called stylo-cerato-hyoidæus.

OMOPLATO-HYOIDÆUS five OMO-HYOIDÆUS vulgo CORACO-HYOIDÆUS.

THIS is a very long small muscle, much narrower than the sterno-hyoidæus, and situated obliquely on the side of the neck or throat, between the scapula and os hyoides.

It is commonly fixed, by the lower extremity, to the superior costa of the scapula, between the small notch and the angle, and sometimes very near the angle.

From thence it passes over the coracoid apophysis, adhering sometimes to it by a kind of aponeurosis, or membranous ligament, and from this adhesion the name of coraco-hyoidæus was given it by some who had not discovered its main insertion.

It is likewise often fixed to the clavicle by ligamentary or fleshy fibres; and has sometimes been seen inserted in the whole middle portion of that bone, being inseparably united with the sterno-hyoidæus.

Having passed the clavicle, it is bent forward, and runs between the sterno-mastoidæus and internal jugular vein, the small middle tendon being situated in this place. From thence it runs up to its insertion in the inferior lateral part of the basis of the os hyoides, near the cornu, and insertion of the sterno-hyoidæus, which it covers a little.

STERNO-HYOIDÆUS five STERNO-CLEIDO-HYOIDÆUS.

THIS is a long, thin, flat muscle, broader at the lower than at the upper part, and situated, together with its fellow, on the fore-side of the throat.

It is fixed, by its lower extremity, in the superior and lateral part of the inner or posterior side of the sternum, in the posterior part of the sternal extremity of the clavicle, in the transverse ligament which connects these two bones, and in the inner or back-side of the cartilage of the first rib. All these other insertions are more considerable than that in the sternum, which is sometimes scarce perceivable.

From thence it runs up on the fore-side of the aspera arteria, joined to its fellow by a membrane, which forms a sort of linea alba, and is inserted laterally in the lower edge of the basis of the os hyoides.

USES of the Muscles which move the Os Hyoides.

THE mechanism observed in the motions of the os hy-

oides, as well as in those of the scapula, is very particular, and very different from what we find in all the other bones of the human body. All these bones have solid fulcra, on which they are either moved or kept fixed by the proper muscles, after the manner of a lever or otherwise; whereas the os hyoides is merely suspended, having nothing to fix it but these very muscles which move it in different manners.

The mylo-hyoidæus represents a moveable floor or bed, which sustains the tongue with its muscles and glands, and forms the bottom of the cavity of the mouth. When the two portions of this muscle act together, they draw the os hyoides a little forward, and fix it in that situation, raising the whole tongue at the same time, and compressing the glandulæ sub-linguales. If one lateral portion acts more than the other, it puts the os hyoides in an oblique situation, and in a condition to serve as a fixed point for the motions of the tongue.

The genio-hyoidæi pull the os hyoides much more forward than the mylo-hyoidæus; and as they are very narrow, and closely united together, there seems to be very little occasion for one of them to act without the other.

The stylo-hyoidæi move the os hyoides upward and backward in a middle direction, between those in which they lie; and they draw it more upward and backward when they act freely; that is, without being checked or confined by other muscles, in the manner which we shall see hereafter. When one acts more than the other, the bone is moved obliquely.

The omo-hyoidæi, or coraco-hyoidæi, act as the stylo-hyoidæi, in a middle direction between the oblique directions in which they lie, and draw the os hyoides downward and backward, when they are not counterbalanced by the stylo-hyoidæi. When one acts more than the other, the bone is drawn obliquely to the right or left hand.

When these muscles and the stylo-hyoidæi act together, the os hyoides is drawn backward by a direct motion compounded of four oblique motions. This compound motion is directed more upward or more laterally, according to the degree of action of the stylo-hyoidæi, or omo-hyoidæi, or of any one muscle of each pair; and in all these motions the four muscles are counterbalanced by the genio-hyoidæi.

The sterno-hyoidæi draw the os hyoides directly downward, and serve to counterbalance the different motions of the stylo-hyoidæi, omo-hyoidæi, and genio-hyoidæi. They may, in some cases, be assisted by the sterno-thyro-hyoidæi, and thyro-hyoidæi, as we shall see hereafter.

According to the method commonly observed in complete treatises of myology, the following muscles remain still to be described, viz. The muscles of the forehead, occiput, palpebræ, eye, external ear, nose, lips, tongue, uvula, ductus Eustachianus, pharynx, larynx, parts of generation, anus, and bladder; and to these we ought even to add the heart, as Mr Cowper has done in the late edition of his Myotomy. But the description of these will be better understood when we treat of the parts to which they belong. See Part VI.

FIG. 1. The MUSCLES immediately under the common teguments on the anterior part of the body, are represented on the right side; and on the left side the MUSCLES are seen which come in view when the exterior ones are taken away.

A, The frontal muscle. B, The tendinous aponeurosis which joins it to the occipital; hence both named occipito-frontalis. C, Attolens aurem. D, The ear. E, Anterior auris. F F, Orbicularis palpebrarum. G, Levator labii superioris alque nasi. H, Levator labiorum communis. I, Zygomaticus minor. K, Zygomaticus major. L, Masteter. M, Orbicularis labiorum. N, Depressor labii inferioris. O, Depressor labiorum communis. P, Buccinator. Q Q, Platysma myoides. R R, Sterno-cleido mastoideus. S, Part of the trapezius. T, Part of the scaleni.

SUPERIOR EXTREMITY.—U, Deltoideus. V, Pectoralis major. W, Part of the latissimus dorsi. X X, Biceps flexor cubiti. Y Y, Part of the brachius externus. Z Z, The beginning of the tendinous aponeurosis, (from the biceps) which is spread over the muscles of the fore-arm. a a, Its strong tendon inserted into the tubercle of the radius. b b, Part of the brachius internus. c, Pronator teres. d, Flexor carpi radialis. e, Part of the flexor carpi ulnaris. f, Palmaris longus. g, Aponeurosis palmaris. 3, Palmaris brevis. 1, Ligamentum carpi annulare. 2 2, Abductor minimi digiti. h, Supinator longus. i, The tendons of the three extensors of the thumb. k, Abductor pollicis. l, Flexor pollicis longus. m m, The tendons of the flexores digitorum communis.—The sheaths are entire in the right hand,—in the left cut open, to shew the tendons of the flexor profundus perforating the sublimis.

MUSCLES not referred to—in the left superior extremity.—n, Pectoralis minor, seu ferratus anticus minor. o, The two heads of (x x) the biceps. p, Coraco-brachialis. q q, The long head of the triceps extensor cubiti. r r, Teres major. f f, Subscapularis. t t, Extensores radiales. u, Supinator brevis. v, The cut extremity of the pronator teres. w, Flexor digitorum sublimis. x, Part of the flexor profundus. y, Flexor pollicis longus. z, Part of the flexor pollicis brevis. 4, Abductor minimi digiti. 5, The four lumbricales.

TRUNK.—6, Serrated extremities of the ferratus anticus major. 7 7, Obliquus externus abdominis. 8 8, The linea alba. 9, The umbilicus. 10, Pyramidalis. 11 11, The spermatic cord. On the left side, it is covered by the cremaster. 12 12, Rectus abdominis. 13, Obliquus internus. 14 14, &c. Intercostal muscles.

INFERIOR EXTREMITIES.—a a, The gracilis.

b b, Parts of the triceps. c c, Pectineus. d d, Psoas magnus. e e, Iliacus internus. f, Part of the gluteus medius. g, Part of the gluteus minimus. h, Cut extremity of the rectus cruris. i i, Vastus externus. k, Tendon of the rectus cruris. l l, Vastus internus. * Sartorius muscle. * * Flehy origin of the tenor vagine femoris or membranofus. Its tendinous aponeurosis covers (i), the vastus externus in the right-side. m m, Patella. n n, Ligament or tendon from it to the tibia. o, Rectus cruris. p, Crureus. q q, The tibia. r r, Part of the gemellus or gastrocnemius externus. f f f f, Part of the soleus or gastrocnemius internus. s, Tibialis anticus. u, Tibialis posticus. v v, Peronæi muscles. w w, Extensor digitorum longus communis. x x, Extensor pollicis longus. y, Abductor pollicis.

FIG. 2. The MUSCLES, GLANDS, &c. of the left side of the face and neck, after the common teguments and platysma myoides have been taken off.

a, The frontal muscle. b, Temporalis and temporal artery. c, Orbicularis palpebrarum. d, Levator labii superioris proprius. e, Levator labiorum communis. f, Zygomaticus. g, Depressor labii inferioris proprius. h, Depressor labiorum communis. i, Buccinator. k, Masteter. l l, Parotid gland. m, Its duct. n, Sterno-cleido mastoideus. o, Part of the trapezius. p, Sterno-hyoidæus. q, Sterno-thyroideus. r, Omo-hyoidæus. s, Levator scapule. t t, Scaleni. u, Part of the splenius.

FIG. 3. The MUSCLES of the face and neck, in view after the exterior ones are taken away.

a a, Corrugator superciliorum. b, Temporalis. c, Tendon of the levator palpebræ superioris. d, Tendon of the orbicularis palpebrarum. e, Masteter. f, Buccinator. g, Levator labiorum communis. h, Depressor labii superioris proprius. i, Sphincter oris. k, Depressor labiorum communis. l, Muscles of the os hyoides. m, Sterno-cleido mastoideus.

FIG. 4. Some of the MUSCLES of the os hyoides, and submaxillary gland.

a, Part of the masteter muscle. b, Posterior head of the digraffic. c, Its anterior head. d d, Sterno-hyoidæus. e, Omo-hyoidæus. f, Stylo-hyoidæus. g, Submaxillary gland in situ.

FIG. 5. The submaxillary gland and duct.

a, Musculus mylo-hyoidæus. b, Hyo-glossus. c, submaxillary gland extra situ. d, Its duct.

FIG. 1. The MUSCLES immediately under the common teguments on the posterior part of the body are represented in the right side;—and on the left side the MUSCLES are seen which come in view when the exterior ones are taken away.

HEAD.—A A, Occipito-frontalis. B, Attollens aurem. C, Part of the orbicularis palpebrarum. D, Masseter. E, Pterygoideus internus.

TRUNK.—Right side. F F F, Trapezius seu cucullaris. G G G G, Latissimus dorsi. H, Part of the obliquus externus abdominis.

TRUNK.—Left side. I, Splenius. K, Part of the complexus. L, Levator scapulae. M, Rhomboides. N N, Serratus posterior inferior. O, Part of the longissimus dorsi. P, Part of the sacro-lumbaris. Q, Part of the semi-spinalis dorsi. R, Part of the serratus anticus major. S, Part of the obliquus internus abdominis.

SUPERIOR EXTREMITY.—Right side. T, Deltoideus. U, Triceps extensor cubiti. V, Supinator longus. W W, Extensores carpi radialis longior & brevis. X X, Extensor carpi ulnaris. Y Y, Extensor digitorum communis. Z, Abductor indicis. 1 2 3, Extensores pollicis.

SUPERIOR EXTREMITY.—Left side. a, Supraspinatus. b, Infra-spinatus. c, Tercus minor. d, Tercus major. e, Triceps extensor cubiti. f f, Extensores carpi radialis. g, Supinator brevis. h, Indicator. 1 2 3, Extensores pollicis. i, Abductor minimi digiti. k, Interosseus.

INFERIOR EXTREMITY.—Right side. l, Gluteus maximus. m, Part of the gluteus medius. n, Fascialis. o, Gracilis. p p, Adductor femoris magnus. q, Part of the vastus internus. r, Semimembranosus. s, Semitendinosus. t, Long head of the biceps flexor cruris. u u, Gastrocnemius externus seu gemellus. v, Tendo Achillis. w, Solcus seu gastrocnemius internus. x x, Peroneus longus & brevis. y, Tendons of the flexor digitorum longus;—and under them flexor digitorum brevis. z, Abductor minimi digiti.

INFERIOR EXTREMITY.—Left side. m, n, o, p p, q, r, s, t, v, w w, x x, y, z. Point the same

parts as in the right side. a, Pyriformis. b b, Gemini. c c, Obturator internus. d, Quadratus femoris. e, Coccygeus. f, The short head of the biceps flexor cruris. g g, Plantaris. h, Popliteus. i, Flexor pollicis longus.

FIG. 2. The palm of the left hand after the common teguments are removed, to shew the MUSCLES of the fingers.

a, Tendon of the flexor carpi radialis. b, Tendon of the flexor carpi ulnaris. c, Tendons of the flexores digitorum. d, Abductor pollicis. e e, Flexor pollicis longus. f, Flexor pollicis brevis. g, Palmaris brevis. h, Abductor minimi digiti. i, Ligamentum carpi annulare. k, A probe put under the tendons of the flexor digitorum sublimis; which are perforated by l, the flexor digitorum profundus. m m m m, Lumbricales. n, Adductor pollicis.

FIG. 3. A fore-view of the foot and tendons of the flexores digitorum.

a, Cut extremity of the tendo Achillis. b, Upper part of the astragalus. c, Os calcis. d, Tendon of the tibialis anticus. e, Tendon of the extensor pollicis longus. f, Tendon of the peroneus brevis. g, Tendons of the flexor digitorum longus, with the nonus Vefalii. h h, The whole of the flexor digitorum brevis.

FIG. 4. MUSCLES of the Anus.

a a, An outline of the buttocks, and upper part of the thighs. b, The testes contained in the scrotum. c c, Sphincter ani. d, Anus. e, Levator ani. f f, Erector penis. g g, Accelerator urinæ. h, Corpus cavernosum urethræ.

FIG. 5. MUSCLES of the Penis.

a a, b, d, e e, f f, h, point the same as in fig. 4. c, Sphincter internus ani. g g, Transversus perinæi.

THE heart throws the blood into two great arteries; one of which is named aorta, the other arteria pulmonalis.

VOL. I. No. 10.

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The aorta distributes the blood to all the parts of the body, for the nourishment of the parts, and for the secretion of different fluids.

3 L

The

The arteria pulmonalis carries the venal blood through all the capillary vessels of the lungs.

Both these great or general arteries are subdivided into several branches, and into a great number of ramifications. In this part, we shall describe the distributions of the aorta, leaving the pulmonary artery to the particular history of the lungs. See Part VI.

The basis of the heart being very much inclined to the right side, and turned a little backward, the aorta goes out from it in a direct course, nearly over-against the fourth vertebra of the back. Its course is direct with respect to the heart; but with respect to all the rest of the body, it ascends obliquely from the left to the right hand, and from before backward.

Soon after this, it bends obliquely from the right hand to the left, and from before backward, reaching as high as the second vertebra of the back; from whence it runs down again in the same direction, forming an oblique arch. The middle of this arch is almost opposite to the right side or edge of the superior portion of the sternum, between the cartilaginous extremities or sternal articulations of the first two ribs.

From thence the aorta descends in a direct course along the anterior part of the vertebrae, all the way to the os sacrum, lying a little toward the left hand; and there it terminates in two subordinate or collateral trunks, called arterie iliacæ.

The aorta is by anatomists generally divided into the aorta ascendens and aorta descendens, though both are but one and the same trunk. It is termed ascendens, from where it leaves the heart to the extremity of the great curvature or arch. The remaining part of this trunk from the arch to the os sacrum or bifurcation, already mentioned, is named descendens.

The aorta descendens is further divided into the superior and inferior portions; the first taking in all that lies above the diaphragm; the other all that lies between the diaphragm and the bifurcation.

The aorta ascendens is chiefly distributed to part of the thorax, to the head and upper extremities. The superior portion of the aorta descendens furnishes the rest of the thorax; the inferior portion furnishes the abdomen and lower extremities.

The great trunk of the aorta, through its whole length, sends off immediately several branches, which are afterwards differently ramified; and these arterial branches may be looked upon as so many trunks with respect to the other ramifications, which again may be considered as small trunks with regard to the ramifications that they send off.

The branches which go out immediately from the trunk of the aorta, may be termed original or capital branches; and of these some are large and others very small.

The large capital branches of the aorta are these: two arterie subclavæ, two carotides, one cæliaca, one mesenterica superior, two renales, formerly termed emulgents, one mesenterica inferior, and two iliacæ.

The small capital branches are chiefly the arterie coronariæ cordis, bronchiales, œsophageæ, intercostales, diaphragmaticæ inferiores, spermaticæ, lumbares, and facræ.

These capital branches or arteries are for the most part disposed in pairs; there being none in odd numbers but the cæliaca, the two mesentericæ, some of the œsophageæ, the bronchialis, and sometimes the facræ.

The aorta gives rise to two small arteries, called coronariæ cordis, which go to the heart and its auricles; one of which is situated anteriorly, the other posteriorly, and sometimes they are three in number.

From the upper part of the arch or curvature, the aorta sends out commonly three, sometimes four large capital branches, their origins being very near each other. When there are four, the two middle branches are termed arteriæ carotides; the other two, subclavæ; and both are distinguished into right and left.

When there are but three branches, which is oftener the case, the first is a short trunk, common to the right subclavian and carotid, the second is the left subclavian, and the third the left carotid.

The origin of the left subclavian terminates the aorta ascendens.

The carotid arteries run up directly to the head, each of them being first divided into two, one external, the other internal. The external artery goes chiefly to the outer parts of the head and dura mater, or first covering of the brain. The internal enters the cranium, through the bony canal of the os petrosum; and is distributed through the brain by a great number of ramifications.

The subclavian arteries separate laterally, and almost transversely, each toward that side on which it lies, behind and under the claviculæ, from whence they have their name.

The subclavian on each side terminates at the upper edge of the first rib, between the lower insertions of the first scalenus muscle; and there, as it goes out of the thorax, takes the name of arteria axillaris.

During this course of the subclavian artery, several arteries arise from it, viz. the mammaria interna, mediastina, pericardia, diaphragmaticæ minor five superior, thymica and trachealis.

The thymica and trachealis on each side are, in some subjects, only branches of one small trunk which spring from the common trunk of the right subclavian and carotid.

They are generally small arteries which run sometimes separate, and sometimes partly separate and partly joined.

The subclavian sends off likewise the mammaria interna, vertebrales, cervicales, and sometimes several of the upper intercostales.

The axillary artery, which is only a continuation of the subclavian from where it goes out of the thorax to the axilla, detaches chiefly the mammaria externa, or thoracica superior, thoracica inferior, scapulares externæ, scapularis interna, humeralis or muscularis, &c. Afterwards it is continued by different ramifications, and under different names, over the whole arm, all the way to the ends of the fingers.

The superior portion of the aorta descendens gives off the arteriæ bronchiales, which arise sometimes by a small common trunk, sometimes separate, and sometimes do not come immediately from the aorta. It next sends off the œsophageæ, which may be looked upon as mediastinæ posteriores;

posteriores; and then the intercostales from its posterior part, which in some subjects come all from this portion of the aorta, in others only the lowest eight or nine.

The inferior portion of the descending aorta, as it passes through the diaphragm, gives off the diaphragmatica inferiores, or phrenicæ; afterwards it sends off several branches, anteriorly, posteriorly, and laterally.

The anterior branches are the cæliaca, which supplies the stomach, liver, spleen, pancreas, &c. the mesenterica superior, which goes chiefly to the mesentery, to the small intestines, and that part of the great intestines which lies on the right side of the abdomen; the mesenterica inferior, which goes to the great intestines on the left side, and produces the hæmorrhoidal interna; and lastly, the right and left arteriæ spermaticæ.

The posterior branches are the arteriæ lumbares, of which there are several pairs, and the sacrae, which do not always come from the trunk of the aorta.

The lateral branches are the cæspitares and adiposæ, the origin of which often varies; the renales, formerly termed emulgents; and the iliacæ, which terminate the aorta by the bifurcation already mentioned.

The iliac artery on each side is commonly divided into the external or anterior, and internal or posterior.

The internal iliac is likewise named arteria hypogastrica; and its ramifications are distributed to the viscera contained in the pelvis, and to the neighbouring parts, both internal and external.

The iliac externa, which is the true continuation of the iliac trunk, goes on to the inguen, and then out of the abdomen, under the ligamentum Fallopii; having first detached the epigastrica, which goes to the musculi abdominis recti. Having quitted the abdomen, it commences arteria cruralis, which runs down upon the thigh, and is distributed by many branches and ramifications to all the lower extremity.

We shall now go on to examine particularly all the capital or original branches of the aorta, from their origin, to the entry of them and of their ramifications into all parts of the body.

The CARDIAC or coronary arteries of the heart arise from the aorta immediately on its leaving the heart. They are two in number, and go out near the two sides of the pulmonary artery, which having first surrounded, they afterwards run upon the basis of the heart in form of a kind of crown, or garland, from whence they are called coronariæ; and then pursue the superficial traces of the union of the two ventricles, from the basis of the heart to the apex, and are afterwards lost in the substance of the heart.

The CAROTID arteries are two in number, one called the right carotid, the other the left. They arise near each other, from the curvature of the aorta, the left immediately, the right most commonly from the trunk of the subclavia on the same side.

They run upon each side of the trachea arteria, between it and the internal jugular vein, as high as the larynx, without any ramification. Each of these trunks is afterwards ramified in the following manner.

The trunk having reached as high as the larynx, is

divided into two large branches or particular carotids, one named external, the other internal, because the first goes chiefly to the external parts of the head, the second enters the cranium, and is distributed to the brain.

The external carotid is anterior, the internal posterior; and the external is even situated more inward, and nearer the larynx, than the other.

The external carotid is the smallest. It runs insensibly outward, between the external angle of the lower jaw, and the parotid gland, which it supplies as it passes. Afterwards it ascends on the fore-side of the ear, and ends in the temples.

In this course it sends off several branches, which may well enough be divided into anterior or internal, and posterior or external; and the principal branches of each kind are these:

The first anterior or internal branch goes out from the very origin of the carotid on the inside; and having presently afterward taken a little turn, and sent off branches to the jugular glands near it, to the fat and skin, it runs transversely, and is distributed to the glandulæ thyroideæ, and to the muscles and other parts of the larynx: It likewise sends some branches to the pharynx and muscles of the os hyoides.

The second anterior branch passes over the nearest cornu of the os hyoides, to the muscles of that bone and the tongue, and to the glandulæ sublinguales; afterwards passing before the cornu of the os hyoides, it loses itself in the tongue, from whence it has been called arteria sublingualis.

The third branch, or arteria maxillaris inferior, goes to the maxillary gland, to the styloid and mastoid muscles, to the parotid and sublingual glands, to the muscles of the pharynx, and to the small flexors of the head.

The fourth branch, arteria maxillaris externa, passes anteriorly on the masseter muscle, and middle of the lower jaw, near the chin. Afterwards it runs under the musculus triangularis labiorum, which it supplies as well as the buccinator and the quadratus menti.

It sends off a particular branch, very much contorted, which divides at the angular commissure of the lips, and running in the same manner along the superior and inferior portions of the musculus orbicularis, it communicates on both sides with its fellow, and thereby forms a kind of arteria coronaria labiorum.

Afterwards it ascends towards the nares, and is distributed to the muscles, cartilages, and other parts of the nose, sending down some twigs which communicate with the coronary artery of the lips. Lastly, it reaches the great angle of the eye, and is ramified and lost on the musculus orbicularis palpebrarum, superciliaris, and frontalis. Through all this course, it is named arteria angularis.

The fifth branch, maxillaris interna, arises over-against the condyle of the lower jaw. It passes behind the condyle, and having given off a twig among the musculi pterygoidei, it is divided into three principal branches.

The first branch, or sphenomaxillaris, goes through the inferior orbitary, or sphenomaxillary fissure, to the orbit, after having supplied the musculi peristaphylini, and

and the glandulous membrane of the posterior nares, through the foramen sphenopalatinum.

It is distributed interiorly and laterally to the parts contained in the orbit, and detaches a small subaltern branch through the extremity of the superior orbitary, or sphenoidal fissure, which enters the cranium, and is spent upon the dura mater.

It sends off likewise another subaltern branch, which passes through the posterior opening of the orbitary canal, and having furnished the maxillary sinus and the teeth, goes out by the inferior orbitary hole, and on the cheek communicates with the angular artery.

The second branch runs through the canal of the lower jaw, and being distributed to the alveoli and teeth, goes out at the hole near the chin, and loses itself in the neighbouring muscles.

The third branch runs up between the internal and external carotids, passes through the foramen spinale of the sphenoidal bone, and is distributed to the dura mater by several ramifications.

The sixth anterior or internal branch, which is very small, is spent on the musculus masseter.

The first external or posterior branch is named arteria occipitalis. It passes obliquely before the internal jugular vein, and having twigs to the musculus stylo-hyoidæus, stylo-glossus, and digastricus, it runs between the styloid and mastoid apophyses, along the mastoid groove, and goes to the muscles and integuments which cover the os occipitis, turning several times in an undulating manner, as it ascends backwards.

The second external branch spreads itself on the outward ear, by a great many small twigs on each side, several of which run inward, and furnish the cartilages, meatus auditorius, skin of the tympanum, and internal ear.

The trunk of the external carotid ascends afterward above the zygoma, passing between the angle of the lower jaw and parotid gland, and forms the temporal artery, which divides into an anterior, middle, and posterior branch.

The anterior branch of the temporal artery goes to the musculus frontalis, communicates with the arteria angularis, and sometimes gives off a very small artery, which pierces the internal apophysis of the os maxillæ all the way to the orbit. The middle branch goes partly to the musculus frontalis, partly to the occipitalis. The posterior branch goes to the occiput, and communicates with the arteria occipitalis. All these branches likewise furnish the integuments.

The internal carotid artery, leaving the general trunk, is at first a little incurvated, appearing as if either it were the only branch of that trunk, or a branch of the trunk of the external carotid.

It is situated a little more backward than the carotis externa, and generally runs up, without any ramification, as high as the lower orifice of the great canal of the apophysis petrosa of the os temporis. It enters this orifice directly from below upward.

At the end of this canal it is again incurvated from below upward, and enters the cranium through a notch of the sphenoidal bone. Then it bends from behind for-

ward, and makes a third angle on the side of the sella sphenoidalis; and again a fourth, under the clinoid apophysis of that sella.

As it leaves the bony canal to enter the cranium, it sends off a branch through the sphenoidal fissure to the orbit and eye, and soon afterwards another through the foramen opticum.

Afterwards the internal carotid runs under the basis of the brain, to the side of the infundibulum, where it is at a small distance from the internal carotid of the other side, and there it commonly divides into two principal branches, one anterior, and one posterior.

The anterior branch runs forward under the brain, first separating from that on the other side, then coming nearer again, it unites with it by an anastomosis, or communication, in the interspace between the olfactory nerves. Afterwards having sent off some small arteries, which accompany these nerves, it leaves its fellow, and divides into two or three.

The first of these branches goes to the anterior lobe of the brain; the second, which is sometimes double, is inverted on the corpus callosum, to which it gives some ramifications, as also to the falx of the dura mater, and middle lobe of the brain. The third goes to the posterior lobe of the brain.

The posterior branch communicates first of all with the vertebral artery of the same side, and then divides into several rami, which run between the superficial circumvolutions of the brain, and are ramified in many different directions on and between these circumvolutions, all the way to the bottom of the sulci.

All these ramifications are covered by the pia mater, in the duplicature of which they are distributed, and form capillary reticular textures in great numbers; and afterwards are lost in the inner substance of the brain.

The SUBCLAVIAN arteries are two in number, one right, the other left; and they arise from the arch of the aorta, on each side of the left carotid, which commonly lies in the middle between them; but when both carotids go out separately, they both lie between the subclavie.

The right subclavian is larger at the beginning than the left, when it produces the right carotid; its origin is likewise more anterior and higher, because of the obliquity of the arch of the aorta. Both of them are distributed much in the same manner, and therefore the description of one may likewise be applied to the other.

The right subclavian, the longest of the two, gives off, first of all, small arteries to the mediastinum, thymus, pericardium, aspera arteria, &c. which are named mediastinum, thymice, pericardie, and tracheales.

Afterward this right subclavian, at about a finger's breadth from its origin, often produces the common carotid of the same side; and at a small finger's breadth from the carotid, it gives off commonly three considerable branches, viz. the mammaria interna, cervicalis, and vertebralis, and sometimes an intercostal artery, which goes to the first ribs, called intercostalis superior.

The arteria thymica communicates with the mammaria interna, and sometimes arises from the anterior middle part of the common trunk of the subclavian and carotid. The

The thymus receives likewise some rami from the mammaria interna, and intercostalis superior.

The pericardium arises much in the same manner with the thymica, and runs down upon the pericardium, all the way to the diaphragm, to which it sends some small ramifications.

The medialina arises sometimes immediately after the thymica, and is distributed principally to the mediastinum.

The trachealis, which may likewise be named gutturalis inferior, runs up from the subclavia, in a winding course, along the aspera arteria, to the glandulae thyroideæ and larynx, detaching small arteries to both sides, one of which runs to the upper part of the scapula.

The internal mammary artery comes from the anterior and lower side of the subclavia, near the middle of the clavicle, and runs down, for about a finger's breadth, behind the cartilages of the true ribs, an inch distant from the sternum.

In its passage, it sends rami to the thymus, mediastinum, pericardium, pleura, and intercostal muscles. It likewise detaches other branches through these muscles, and between the cartilages of the ribs, to the pectoralis major, and other neighbouring muscular portions; to the mammae, membrana adiposa, and skin.

Afterwards it goes out at the thorax, on one side of the appendix eniformis, and is lost in the musculus abdominis rectus, a little below its upper part.

The cervical artery arises from the upper side of the subclavian, and is presently afterward divided into two, which come out, sometimes separately, sometimes by a small common trunk. The largest of these two arteries is anterior, the other posterior.

The anterior cervicalis, running behind the carotid of the same side, is distributed to the musculus coraco-hyoidæus, mastoidæus, cutaneus, sterno-hyoidæus, and sterno-thyroidæus; to the jugular glands, the aspera arteria, the muscles of the pharynx, bronchia, œsophagus; and to the anterior muscles which move the neck and head.

The posterior cervicalis arises sometimes a little after the vertebralis, and sometimes from that artery. It passes under the transverse apophysis of the last vertebra of the neck, and sometimes through a particular hole in that apophysis; and from thence runs up backward in a winding course, on the vertebral muscles of the neck, and then returns in the same manner.

The vertebral artery goes out from the posterior and upper side of the subclavian, almost opposite to the mammaria interna and cervicalis. It runs up through all the holes in the transverse apophyses of the vertebrae of the neck, and, in its passage, sends off little twigs, through the lateral notches of these vertebrae, to the medulla spinalis and its coverings. It also gives arteries to the vertebral muscles, and to other muscles near them.

It sends off a small branch, which is ramified on the outer and posterior parts of the occiput, and communicates with the cervical and occipital arteries. Having afterwards reached the great foramen of the os occipitis, it enters the cranium, and pierces the dura mater.

As soon as it enters the cranium, it sends several small

ramifications to the back-part of the medulla oblongata, and to the corpora olivaria and pyramidalia, which are likewise spread on the back sides of the fourth ventricle of the brain, and form the plexus choroides of the cerebellum.

Afterwards it advances on the apophysis basilaris of the os occipitis, inclining, by small degrees, toward the vertebral artery of the other side, all the way to the extremity of that apophysis, where they both join in one common trunk.

The arteria basilaris runs forward under the great transverse protuberance of the medulla oblongata, to which it gives ramifications, as well as to the neighbouring parts of the medulla.

The spinal arteries are two in number, one anterior, and one posterior; both produced by both vertebrales, each of which, as soon as it enters the cranium, sends out a small branch, by the union of which the posterior spinalis is formed. Afterwards the vertebrales advancing on the apophysis basilaris, or production of the occipital bone, detach backward two other small branches, which likewise meet, and, by their union, form the spinalis anterior. These spinal arteries run down on the fore and back sides of the medulla spinalis, and, by small transverse ramifications, communicate with those which the intercostal and lumbar arteries send to the same part.

The internal auditory artery goes off from each side of the arteria basilaris, to the organ of hearing, accompanying the auditory nerve, having first furnished several small twigs to the membrana arachnoides.

The posterior meningæa arises from the same trunk with the auditoria interna, and goes to the back-part of the dura mater, on the occipital and temporal bones, and supplies the neighbouring lobes of the brain.

When the superior intercostal artery does not go out from the trunk of the aorta descendens, it commonly arises from the lower side of the subclavian, and runs down on the inside of the two, three, or four uppermost true ribs, near their heads, and sends off, under each rib, a branch, which runs along the lower edge, and supplies the intercostal muscles and neighbouring parts of the pleura.

These branches, or particular intercostal arteries, communicate with each other at different distances by small rami, which run upward and downward from one to the other, on the intercostal muscles.

The ductus arteriosus, which is found only in the fetus and in very young children, arises from the aorta descendens, immediately below the left subclavian artery. In adults, this duct is shrunk up and closed, and appears only like a short ligament adhering by one end to the aorta, and by the other to the pulmonary artery, so that in reality it deserves no other name than that of ligamentum arteriosum.

The bronchial arteries go sometimes from the fore-side of the superior descending aorta, sometimes from the first intercostal, and sometimes from the arteria œsophagea. Sometimes they arise separately from each side, to go to each lung, and sometimes by a small common trunk, which afterwards separates towards the right and left hand, at the bifurcation of the aspera arteria, and accompany the ramifications of the bronchia.

The bronchialis gives a small branch to the neighbouring auricle of the heart, which communicates with the arteria coronaria.

The œsophagus are generally two or three in number, sometimes but one. They arise anteriorly from the aorta descendens, and are distributed to the œsophagus, &c.

The inferior intercostals are commonly seven or eight on each side, and sometimes ten, when the superior intercostals arise likewise from the aorta descendens; in which case these run obliquely upward.

They arise along the back-side of the descending aorta in pairs, all the way to the diaphragm, and run transversely towards each side, on the bodies of the vertebrae. Those on the right side pass behind the vena azygos; and afterwards they all run to the intercostal muscles, along the lower edge of the ribs, all the way to the sternum, or near it.

They send branches to the pleura, to the vertebral muscles, to those muscles which lie on the outsides of the ribs, and to the upper portions of the muscles of the abdomen; and they communicate with the arteriæ epigastricæ and lumbares.

Before they take their course along the ribs, each of them detaches one branch between the transverse apophyses on both sides, to the vertebral muscles, and another which enters the great canal of the spina dorsi.

Afterwards each intercostal artery having reached the middle of the rib, or a little more, divides into two principal branches, one internal, the other external. Soon after this division, the arteries that run upon the false ribs, separate a little from them, being gradually bent downward one after another, and are spread upon the abdominal muscles.

The subclavian artery having left the thorax immediately above the first rib, in the interspace left between the portions of the scalenus, there receives the name of axillaris, because it passes under the axilla.

In this course it gives off, from its inside, a small branch to the inside of the first rib; and afterwards four or five principal branches, viz. the thoracica superior, or mammaria externa, thoracica inferior, muscularis, or scapularis externa, scapularis interna, and humeralis.

The superior thoracica, or external mammary artery, runs down, in a winding course, on the lateral parts of the thorax, and crosses the ribs. It gives branches to the two pectoral muscles, to the mamma, musculus subclavius, ferratus major, latissimus dorsi, and to the upper portions of the coraco-brachialis and biceps.

The inferior thoracic artery runs along the inferior costa of the scapula, to the musculus subscapularis, teres major and minor, infra-spinatus, latissimus dorsi, ferratus major, and the neighbouring intercostal muscles, communicating with the arteriæ scapulares.

The external scapulary artery passes through the notch in the superior costa of the scapula, to the musculus supra-spinatus and infra-spinatus, teres major and minor, and to the articulation of the scapula with the os humeri.

The internal scapulary artery arises from the axillary artery near the axilla, and runs backward, to be distributed to the subscapularis, giving branches to the ferratus major, to the axillary glands, and to the teres major.

The humeral artery arises from the lower and fore-side of the axillaris, and runs backward between the head of the os humeri and teres major, surrounding the articulation, till it reaches the posterior part of the deltoides, to which it is distributed.

During this course, it gives several branches to the superior portions of the anconæi, to the capsular ligament of the joint of the shoulder, and to the os humeri itself, through several holes immediately below the great tuberosity of the head of that bone.

Opposite to the origin of this humeral artery, the axillaris sends off another small branch, which runs in a contrary direction, between the head of the os humeri, and the common upper part of the biceps and coraco-brachialis; and having given branches to the vagina and channel of the biceps, and to the periosteum, afterwards joins the principal humeralis.

The axillary artery having given off these branches, passes immediately behind the tendon of the pectoralis major, where it changes its former name for that of arteria brachialis. It runs down on the inside of the arm, over the musculus coraco-brachialis and anconæus internus, and along the inner edge of the biceps, behind the vena basilica, giving small branches on both sides to the neighbouring muscles, to the periosteum, and to the bone.

Between the axilla and middle of the arm, it is covered only by the skin and fat; but afterwards it is hid under the biceps, and runs obliquely forward as it descends; being at some distance from the internal condyle, but it does not reach the middle of the fold of the arm.

Between the axilla and this place, it sends off many branches to the infra-spinatus, teres major and minor, subscapularis, latissimus dorsi, ferratus major, and other neighbouring muscles, to the common integuments, and even to the nerves. Below the fold of the arm, it divides into two principal branches, one called arteria cubitalis, the other radialis.

From its upper and inner part, it sends off a particular branch, which runs obliquely downward and backward over the anconæi, and then turns forward again, near the external condyle, where it communicates with a branch of the arteria radialis.

Immediately below the insertion of the teres major, it gives off another branch, which runs from within outwards, and from behind forward, round the os humeri; and descends obliquely forward, between the musculus brachiiæus, and anconæus externus, to both which it is distributed in its passage. Having afterwards reached the external condyle, it unites with the branch last mentioned, and likewise communicates with a branch of the arteries of the fore-arm, so that there is here a triple anastomosis.

About the breadth of a finger below this second branch, the brachial artery sends off a third, which runs down towards the internal condyle, and communicates with other branches of the arteries of the fore-arm, as we shall see hereafter.

About the middle of the arm, or a little lower, much about the place where the brachial artery begins to be covered by the biceps, it sends off a branch, which is distributed

distributed to the periosteum, and penetrates the bone, between the musculus brachii and anconus internus.

About an inch lower, it gives off another branch, which having furnished ramifications to the anconus internus, runs over the inner condyle, and likewise communicates with branches of the arteries of the fore-arm.

Having got below the middle of the arm, the brachial artery detaches another branch, which runs behind the inner condyle, in company with a considerable nerve; and having passed over the muscles inserted in this condyle, it communicates with that branch of the cubital artery which encompasses the fold of the arm.

A little lower, it sometimes sends out another branch, which passes on the fore-side of the inner condyle, and then communicates with a branch which runs up from the cubital artery. These three communicating branches are termed collateral arteries.

The common trunk of the brachial artery having reached the fold of the arm, runs, together with a vein and a nerve, immediately under the aponeurosis of the biceps, and passes under the vena mediana, detaching branches on each side to the neighbouring muscles.

About a large finger's breadth beyond the fold of the arm, this artery divides into two principal branches, one inner or posterior, named cubitalis; the other outer or anterior, named radialis.

From this bifurcation, the brachial artery sends branches on each side, to the supinator longus, pronator teres, fat, and skin. It sometimes, though very rarely, happens, that this artery is divided from its origin into two large branches, which run down on the arm, and afterwards on the fore-arm, where they have the names of cubitalis and radialis.

The cubital artery sinks in between the ulna and the upper parts of the pronator teres, perforatus, ulnaris gracilis, and radialis internus; then leaving the bone, it runs down between the perforatus and ulnaris internus, all the way to the carpus and great transverse ligament, and sends out several branches.

The first is a small artery, which runs inward to the inner condyle, and then turns upward, like a kind of recurrent, to communicate by several branches with the collateral arteries of the arm, already mentioned, and particularly with the third. A little lower down, another small branch goes off, which having run upward a little way, and almost surrounded the articulation, communicates with the second collateral artery of the arm, between the olecranon and inner condyle.

Afterwards, the cubital artery having, in its course between the heads of the ulna and radius, reached the interosseous ligaments, sends off two principal branches, one internal, the other external, called the interosseous arteries of the fore-arm.

The external artery pierces the ligament about three fingers breadth below the articulation, and presently afterwards gives off a branch, which runs up, like a recurrent, toward the external condyle of the os humeri, under the ulnaris externus and anconus minimus, to which it is distributed, as also to the supinator brevis.

Afterward, this external interosseous artery runs down on the outside of the ligament, and is distributed to the

ulnaris externus, extensor digitorum communis, and to the extensores pollicis indicis and minimi digiti; communicating with some branches of the internal interosseous artery.

Having reached the lower extremity of the ulna, it unites with a branch of the internal interosseous artery, which, at this place, runs from within outward, and is distributed, together with it, on the convex side of the carpus and back of the hand; communicating with the arteria radialis, and with a branch of the cubitalis.

By these communications, this artery forms a sort of irregular arch, from whence branches are detached to the external interosseous muscles, and to the external lateral parts of the fingers.

The internal interosseous artery runs down very close to the ligament, till it reaches below the pronator teres, between which and the pronator quadratus, it perforates the ligament, and goes to the convex side of the carpus and back of the hand, where it communicates with the external interosseous artery, with the radialis and internal branches of the cubitalis.

From the origin of the two interosseous, the cubital artery runs down between the perforatus, perforans, and ulnaris internus, along the ulna, sending branches to the neighbouring parts.

Afterward, it passes over the internal transverse ligament of the carpus, by the side of the os pisiforme, and having furnished the skin, palmaris brevis, and metacarpus, it slips under the aponeurosis palmaris, giving off one branch to the hypotenar minimi digiti, and another, which runs toward the thumb, between the tendons of the flexors of the fingers, and the bases of the metacarpal bones.

It likewise sends off a branch, which, running between the third and fourth bones of the metacarpus, reaches to the back of the hand, where it communicates with the external interosseous artery. Afterwards, having supplied the interosseous muscles, it communicates with the radialis; and they both form an arterial arch, in the hollow of the hand.

This arch sends from its concave side, towards the second phalanx of the thumb, a branch for the lateral internal part thereof, and then ends near the head of the first metacarpal bone, by a communication with the radialis, having first given a branch to the fore-side of the index, and another to the side of the thumb next the former. These communicate, at the ends of the fingers, with the neighbouring branches, as in the other fingers.

This arch sends likewise small twigs to the interosseous muscles, to the lumbricales, p. lmaris, and to other neighbouring parts; and, lastly, to the integuments.

The radial artery begins by detaching a small branch, which runs upward like a recurrent toward the fold of the arm, and turns backward round the external condyle, communicating with the neighbouring branches from the trunk of the brachial artery.

It runs down along the inside of the radius, between the supinator longus, pronator teres, and the integuments, giving branches to these muscles, and likewise to the perforatus, perforans, and supinator brevis. From thence it runs, in a winding course, towards the extremity of the

the radius, supplying the flexors of the thumb and pronator quadratus.

Having reached the extremity of the radius, it runs nearer the skin, especially toward the anterior edge of the bone, being the artery which we feel there when we examine the pulse.

At the end of the radius, it gives off a branch to the thenar; and, after having communicated with the arch of the cubital artery in the palm of the hand, and set off some cutaneous branches at that place, it detaches one along the whole internal lateral part of the thumb.

Afterwards it runs between the first phalanx and tendons of the thumb, to the interstice between the basis of this first phalanx, and of the first metacarpal bone, where it turns to the hollow of the hand.

At this turning, it sends off a branch to the external lateral part of the thumb, which having reached the end thereof, communicates, by a small arch, with the branch which goes to the internal lateral part.

It likewise sends branches outward, which run between the two first bones of the metacarpus, and the two tendons of the radialis externus; and it communicates with an opposite branch of the cubitalis, together with which it furnishes the external interosseous muscles and integuments of the back of the hand and convex side of the carpus.

Lastly, the radial artery terminates, in its passage over the semi-interosseous muscle of the index, near the basis of the first metacarpal bone, and as it runs under the tendons of the flexor muscles of the fingers, where it is joined to the arch of the cubitalis.

It sends off another branch, which runs along the fore-part of the first bone of the metacarpus, to the convex side of the index, where it is lost in the integuments.

The left DIAPHRAGMATIC artery goes out commonly from the aorta descendens, as it passes between the crura of the small muscle of the diaphragm. The right diaphragmatic comes sometimes from the nearest lumbar artery, but most commonly from the celiacæ. These arteries likewise have the name of arterie phrenicæ.

They appear almost always in several ramifications on the concave or lower side of the diaphragm, and seldom on the upper or convex side. They give small branches to the glandulæ renales, or capsulæ atrabilaria.

They send likewise small branches to the fat which lies upon the kidneys, from whence they have the name of arterie adiposæ.

Besides these capital diaphragmatic arteries, there are others of a subordinate class, which come from the intercostales, mammarie interne, mediastine, pericardie, and celiacæ.

The celiacæ artery arises anteriorly, and a little to the left hand, from the aorta descendens, immediately after its passage through the small muscle of the diaphragm, nearly opposite to the cartale, between the last vertebra of the back, and the first of the loins. The trunk of this artery is very short; and near its origin, it sends off from the right side two small diaphragmaticæ, though sometimes there is only one, which goes to the right

hand, and is afterwards distributed both ways; communicating with the other arteries of the same name, which come from the intercostales and mammarie. The left branch sends rami to the superior orifice of the stomach, and to the glandula renalis on the same side; the right furnishes the pylorus, and the renal gland on the right side.

Immediately after this, the celiacæ gives off a considerable branch, named arteria ventriculi coronaria, and gastrica, or gastrica superior; and then it presently divides into two large branches, one toward the right hand, named arteria hepatica; the other to the left, called splenica.

The coronary artery of the stomach goes first to the left side of that organ, a little beyond the superior orifice; round which orifice it throws branches, and also to every part of the stomach near it; and these branches communicate with those which run along the bottom of the stomach to the pylorus.

Afterwards it runs on the right side of the superior orifice, along the small curvature of the stomach, almost to the pylorus, where it communicates with the arteria pylorica; and turning towards the small lobe of the liver, it gives off some branches to it.

Then it advances, under the ductus venosus, to the left lobe of the liver, in which it loses itself near the beginning of the duct, having first given off some small branches to the neighbouring parts of the diaphragm and omentum.

As soon as the hepatic artery leaves the celiacæ, it runs to the upper and inward part of the pylorus, in company with the vena portæ, sending off two branches, a small one called arteria pylorica, and a large one named gastrica dextra, or gastrica major.

The pylorica is ramified on the pylorus, and having distributed branches to the neighbouring parts of the stomach, which communicate with those of the right gastrica, it terminates on the pylorus, by an anastomosis with the coronary artery of the stomach.

The right gastric artery having passed behind and beyond the pylorus, sends out a considerable branch, named arteria duodenalis, or intestinalis, which sometimes comes from the trunk of the hepatica, as we shall see hereafter. Afterwards this gastric artery runs along on the right side of the great curvature of the stomach, to the neighbouring parts of which, on both sides, it distributes branches.

These branches communicate with those of the arteria pylorica, and of the coronaria ventriculi, and with the right gastro-epiploicæ, which furnish the nearest part of the omentum, and communicate with the mesenterica superior. After this, the right gastric artery ends in the left, which is a branch of the splenica.

The duodenal or intestinal artery runs along the duodenum on the side next the pancreas; to both which it furnishes branches, and also to the neighbouring part of the stomach.

The hepatic artery, having sent out the pylorica and right gastrica, advances behind the ductus hepaticus, toward the vesicula fellis, to which it gives two principal branches

branches called arteria cystica; and another named bilaria, which is lost in the great lobe of the liver.

Afterwards, this artery enters the fissure of the liver, and joins the vena portæ, with which it runs within a membranous vagina, called capsula Glissoni, and accompanies it through the whole substance of the liver by numerous ramifications, which may be termed arteria hepatica propria.

Before it enters the liver, it gives small branches to the external membrane of this viscus, and to the capsula Glissoni.

Immediately after the origin of the splenic artery from the cæliaca, it runs toward the left hand, under the stomach and pancreas, to the spleen. It adheres closely to the posterior part of the lower side of the pancreas, to which it gives several branches, named arteria pancreaticæ.

Near the extremity of the pancreas, under the left portion of the stomach, the splenic artery gives off a principal branch, called gastrica sinistra or minor, which runs from left to right along the left portion of the great curvature of the stomach, giving branches to both sides of this portion, which communicate with those of the coronaria ventriculi.

This gastric artery sends likewise another branch at least to the extremity of the pancreas, which communicates with the other pancreatic arteries. It also supplies the omentum with branches, termed gastrico-epiploica sinistra; and then it communicates with the right gastric; and from this union, the gastro-epiploicae mediæ are produced.

Afterwards, the splenic artery advances towards the spleen, in a course more or less contorted; but before it arrives at that viscus, it gives two or three branches to the large extremity of the stomach, commonly called vasa brevia; and one to the omentum, named epiploica.

At the spleen, this artery divides into four or five branches, which enter that viscus, after having given some small twigs to the neighbouring parts of the stomach and omentum.

The superior mesenteric artery arises anteriorly from the lower portion of the descending aorta, a very little way below the cæliaca, going out a little towards the right hand, but bending immediately afterwards to the left.

Near its origin, it gives off a small branch, which dividing into two, goes to the lower side of the head of the pancreas, and neighbouring part of the duodenum, communicating with the intestinalis by small arches, and areolæ or meshes.

Afterwards it passes over the duodenum, between this intestine and the meseraic vein, between the two laminae of the mesentery; and then bending in an oblique direction from left to right, and from above downward, by very small degrees, it advances toward the extremity of the ileum. By this incurvation, it forms a kind of long arch, from the convex side of which a great many branches go out.

These branches are sixteen or eighteen in number, or thereabouts, and almost all of them are bestowed on the small intestines, from the lower third part of the duodenum to the cæcum and colon.

As they approach the intestines, all these branches communicate, first by reciprocal arches; then by areolæ and meshes of all kinds of figures; from which is detached an infinite number of small ramifications, which surround the intestinal canal, like an annular piece of network.

The first branches from the convex side of the mesenteric arch, which are very short, supply the pancreas and mesocolon, and communicate with the duodenal artery. The last branches go to the appendicula vermiculiformis, and send a portion of an arch to the beginning of the colon.

The considerable branches from the concave side of the mesenteric arch, are seldom above two or three in number; but before they arise, a small ramus goes out to the duodenum, and gives some very small arteries to the pancreas.

The first considerable branch from the concave side of the arch goes into the mesocolon towards the right portion of the colon.

The second principal branch, having run for some space through the mesentery, divides into three rami; the first of which goes to the lower part of the right portion of the colon, the second goes to the beginning of the colon and intestinum cæcum.

The third ramus of the second branch, having communicated with the second, gives small twigs to the cæcum, appendicula vermiculiformis, and extremity of the ileum.

The lower mesenteric artery goes out anteriorly from the aorta descendens inferior, about a finger's breadth or more above the bifurcation, and below the spermatic arteries; and having run about the length of an inch, or something more, it is divided into three or four branches.

The first or superior branch, about an inch from its origin, divides into two rami; the first of which runs along the left portion of the colon. The second ramus having communicated with the first, runs down upon the same portion of the colon.

The middle branch divides into two rami; one of which passes upward on the extremity of the colon, communicating by arches with the second ramus of the superior branch; the other runs down on the extremity of the same intestine.

The lower branch goes to the second portion of the colon, or to both.

It sends another considerable branch downward, called arteria hæmorrhoidal interna, which runs down behind the intestinum rectum, to which it is distributed by several ramifications.

The renal arteries, commonly called emulgents, are ordinarily two in number, and go out laterally from the inferior descending aorta, immediately under the mesenterica superior, one to the right hand, the other to the left.

They run commonly without division, and almost horizontally to the kidneys, into the depressions of which they enter by several branches, which form arches in the inner substance of these viscera.

From these arches, numerous small rami go out toward

ward the circumference or outer surface of the kidneys.

Ordinarily, the right renal artery passes behind the vena cava and renal vein on the other side; and the left artery, first behind and then before the vein.

The arteries of the renal glands, which may be termed arterie capsulares, arise sometimes from the aorta above the arteria renalis, and give out the arterie adiposæ, which go to the fat of the kidneys. Sometimes they come from the trunk of the cæliaca. The right capsular artery comes most commonly from the arteria renalis of the same side, near its origin; the left from the aorta, above the renalis.

The spermatic arteries are commonly two in number, sometimes more. They are very small, and go out anteriorly from the aorta descendens inferior, near each other, about a finger's breadth below the arterie renales, between the two mesentericæ, or between the renales and mesentericæ inferiores.

They send off to the common membrane of the kidney small branches, named arterie adiposæ; and afterwards they run down upon the psoas muscles, on the fore-side of the ureters, between the two laminæ of the peritoneum.

They give several considerable branches to the peritoneum, and communicate both with the mesentericæ and adiposæ. They likewise send small arteries to the ureters.

Afterwards, they pass in men through the tendinous openings of the abdominal muscles in the vagina of the peritoneum, and are distributed to the testicles and epididymis, where they communicate with a branch of the iliaca externa.

In women they do not go out of the abdomen, but are distributed to the ovaria and uterus, and communicate with branches of the hypogastrica, at the jagged extremities of the tubæ Fallopianæ.

The lumbar arteries go out posteriorly from the inferior descending aorta, in five or six pairs, or more, much in the same manner with the intercostals.

They may be divided into superior and inferior. The superior send small branches to the neighbouring parts of the diaphragm and intercostal muscles, and supply the place of femi-intercostal arteries.

They are distributed on each side to the psoas muscles, to the quadrati lumborum, and to the oblique and transverse muscles of the abdomen; and by perforating the oblique muscles, they become external hypogastric arteries. They go likewise to the vertebral muscles, and to the bodies of the vertebrae, and enter the spinal canal through the lateral notches, to go to the membranes, &c. forming rings much in the same manner with the intercostals.

The arterie sacræ go out commonly from the back part of the inferior descending aorta, at the bifurcation. They are two, three, or four in number, and sometimes but one. They are ramified on the os sacrum, and on the neighbouring parts of the peritoneum, intestinum rectum, fat, &c. and enter the canal of that bone through the anterior holes, being there distributed toward each side. They likewise send small arteries to the large fasciculi of nerves, which go out through the holes of the os sacrum, and they penetrate the inner substance of that bone.

The inferior descending aorta ends at the last vertebra of the loins, and sometimes higher, in two large lateral branches, one on the right hand, the other on the left, called arterie iliacæ; each of which is a common trunk to two other arteries of the same name. This bifurcation lies on the anterior and left side of that of the vena cava.

The primitive iliac arteries divaricate gradually as they descend, advancing obliquely toward the anterior and lower part of the ossa ilium, without any considerable ramification for about the breadth of three fingers, except a few very small arteries that go to the os sacrum. They likewise give small arteries to the peritoneum, to the coats of the veins, and to the fat and ureters.

The right iliac trunk passes first on the foreside of the origin of the left iliac vein, and runs down on the foreside of the right vein, almost to the place where it goes out of the abdomen, its course being there directed more inwardly. The left trunk goes down likewise before the left vein, but lies a little toward the inside as it leaves the abdomen.

About three fingers breadth from their origin, each iliac trunk is divided into two secondary arteries, one external, the other internal. The external artery has no particular name; the internal is termed hypogastrica.

The external iliac on each side runs down on the iliac muscle to the ligamentum Fallopii, under which it goes out of the abdomen. In this course, it gives off only a few small arteries to the peritoneum, and other parts near it; but as it passes out of the abdomen under the ligament, it detaches two considerable branches, one internal, the other external.

The internal branch is named arteria epigastrica, and goes out anteriorly from the external iliac. From thence it runs obliquely upward on the tendon of the transverse muscle towards the posterior part of the rectus.

Afterwards the epigastric artery runs up along the posterior or inner side of this muscle, sending ramifications to the tendons of the neighbouring muscles, &c. and then loses itself by a true anastomosis of several ramifications, with the mammaria interna.

The external branch of the outer iliac goes off laterally from the outside of that artery under the ligamentum Fallopii, and from thence to the internal labium of the os ilium, where it divides into two, and is ramified on the oblique and transverse muscles of the abdomen communicating with the arteria lumbaris.

Besides these two branches, the external iliac gives off a small ramus internally, under the ligament, which runs to the vagina of the spermatic rope; and sometimes another small twig goes from the outside to the os ilium.

The internal iliac or hypogastrica, having run a little more than a finger's breadth inward and backward, bends by small degrees obliquely forward, and toward the outside; and afterwards contracting in its dimensions, it ends in the umbilical artery, which ought to be looked upon as a true continuation of the trunk of the hypogastrica.

This arteria umbilicalis ascends on the side of the bladder, and having detached small rami to that viscus and to the neighbouring parts of the peritoneum, &c. it contracts, and in adults is quite closed up above the middle

middle of the bladder. It likewise gives branches to the uterus, and to the neighbouring parts in both sexes. Afterwards it ascends in form of a ligament to the umbilicus, where it joins the umbilical artery on the other side.

From the convex side of the curvature of the hypogastric artery, four or five principal branches commonly go out very near each other, viz. iliac minor, glutea, sciatica, pudica communis, five pudica hypogastrica, and obturatrix.

The iliac minor, the most posterior of these branches, and which is often no more than a ramus of the glutea, passes between the last two lumbar nerves, and divides into two rami, one of which enters the canal of the os sacrum through the lowest large anterior holes; the other passes behind the musculus psoas, to which it gives twigs, and behind the crural nerve, being afterwards distributed to the iliac muscle, and to the middle part of the inside of the os ilium, penetrating into the substance of the bone sometimes by one hole, sometimes by more.

The arteria glutea is sometimes the largest of all the hypogastric branches. Near its beginning it sometimes sends out the iliac minor, and sometimes the small ramus that goes from that artery to the os sacrum and other parts fixed to that bone. Afterwards this artery goes out of the pelvis, in company with the sciatic nerve, through the upper part of the great sinus of the os innominatum, below the musculus pyriformis, and is distributed, in a radiated manner, to the gluteus maximus and medius.

In its passage, it gives some branches to the os sacrum, os coccygis, musculus pyriformis, the muscles of the anus, and to the neighbouring parts of the intestinum rectum, forming a particular haemorrhoidal interna. It likewise sends twigs to the bladder and parts near it; and detaches a pretty long branch, which runs down with the sciatic nerve.

The arteria sciatica gives first of all some branches to the musculus pyriformis, the quadrigemini, the os sacrum, &c. and even to the inner side of the os ischium. It likewise detaches a branch, which runs under the musculus quadratus, to the articulation of the os femoris.

The pudica communis, called commonly pudica interna, arises sometimes by a trunk common to it and to the glutea, and gives out two principal branches; the first of which passes through the great sinus of the os ilium, in company with the glutea and sciatica, and then divides into two rami.

The first ramus goes behind the spine of the ischium, between the two ligaments which lie between that bone and the os sacrum; and runs on the inside of the tuberculum ischii, all the way to the origin of the corpus cavernosum penis. There it divides into several arteries, one of which goes to the sphincter ani, under the name of haemorrhoidal externa.

The rest are distributed to the neighbouring integuments, to the bulb of the urethra, and to the corpus cavernosum penis; but the last of these arteries, or rather the extremity of this first ramus, runs from behind forward, over the neck of the os femoris, and communicates with a branch of the arteria cruralis.

The second principal ramus, called commonly arteria pudica externa, runs between the bladder and intestinum rectum, and is distributed in men to the vesiculae seminales, neck of the bladder, prostate gland, and neighbouring parts of the rectum.

Afterwards it runs under the os pubis on the side of a considerable vein, which lies directly under the symphysis; and it runs along the penis between this vein and a nerve, being distributed in its passage to the corpus cavernosum, and communicating with the pudica minor, which comes from the cruralis.

This second branch of the pudica major goes off sometimes separately from the hypogastrica, especially in women, being distributed to the lateral parts of the uterus, where it communicates with the spermatic artery, near the jagged extremity of the tuba Fallopiana, and to the neighbouring parts of the vagina, &c.

The arteria obturatrix perforates the obturator muscles, and goes out of the pelvis at the upper part of the ligament of the foramen ovale, having first sent a small branch over the symphysis of the os ilium and os pubis, to the inguinal glands and integuments.

As it passes by the muscles, it divides and is distributed to the pectineus and triceps. It likewise sends out another branch, which communicates with that branch of the sciatica that goes to the articulation of the os femoris; and gives small arteries to the holes in the neck of that bone.

The iliac artery goes out of the abdomen, between the ligamentum Fallopii and tendon of the psoas, at the union of the os ilium and os pubis, and there it takes the name of arteria cruralis.

It sends off, first of all, three small branches; one of which, called pudica externa, goes over the crural vein to the skin and ligament of the penis, and to the inguinal glands, communicating with the pudica interna. The second goes to the musculus pectineus; and the third to the upper part of the sartorius. All these branches furnish likewise the neighbouring anterior integuments.

Afterwards the crural artery runs down on the head of the os femoris; and, by taking a particular turn, gets on the inside of the crural vein, about three fingers breadth from where it goes out of the abdomen.

In changing its situation, it sends out three considerable branches, one external, one middle, and one internal.

The external branch runs on the upper side of the thigh to the crureus, vastus externus, rectus anterior, musculus fasciae latae, and gluteus medius; sending up a ramus to the apex of the great trochanter, which communicates with the first principal ramus of the pudica major and sciatica.

The middle branch runs down on the inside of the thigh between the triceps muscles, to which it gives several rami, one whereof perforates the second muscle, and is distributed to the gluteus maximus, semi-nervosus, semi-membranosus, biceps, and to the neighbouring integuments.

The internal branch runs backward on the quadrigemini, towards the great trochanter; and having detached a ramus, which goes into the joint of the os femoris,

it runs downward, and gives rami to all the muscles that lie on the backside of that bone, one of which enters the bone itself on one side of the linea aspera.

Having sent off all these three branches, the arteria cruralis runs down between the sartorius, vastus internus, and triceps, giving branches to all the parts near it. It is covered by the sartorius all the way to the lower part of the thigh, where it is inflected backward over the triceps tertius a little above the internal condyle of the os femoris. Afterwards, continuing its course through the hollow of the ham, it is called arteria poplitea.

The poplitea, while in the ham, is covered only by the integument, sending off branches toward each side, which run up upon the condyles, and communicate with the lower ramifications of the arteria cruralis.

It sends rami to the joint of the knee, one of which at least passes between the crucial ligaments. As it runs down, it sends branches to the gastrocnemii and popliteus; and having reached the backside of the head of the tibia, it gives off two branches, one to each side.

The first or internal branch surrounds the fore-part of the head of the tibia, passing between the bone and internal lateral ligament; and besides several other ramifications, sends up a small branch, which communicates with the arteries that lie round the condyles of the os femoris.

The second or external branch runs over the head of the fibula, and between the head of the tibia and external lateral ligament of the knee, surrounding the articulation all the way to the ligament of the patella, and communicating with the branches which lie round the condyles of the os femoris, together with a branch of the first or internal ramus.

Immediately after the origin of these two rami, and before the poplitea ends, it sends a small artery down on the backside of the interosseous ligament, very near the tibia, into which it enters by a particular hole a little above the middle portion of the bone.

As the poplitea ends, it divides into two principal branches, one of which runs between the heads of the tibia and fibula, passing from behind forwards on the interosseous ligament, where it takes the name of arteria tibialis anterior. The second branch divides into two others; one internal and largest, called arteria peronæa anterior; the other posterior and smallest, named arteria peronæa posterior.

The tibialis anterior, having passed between the heads of the tibia and fibula, sends small branches upward and laterally. The superior branches communicate with those rami of the popliteus which lie round the articulation; and the lateral branches go to the neighbouring parts. Afterwards this tibial artery runs down on the foreside of the interosseous ligament, toward the outside of the tibia, between the musculus tibialis anticus and extensor pollicis.

Having run laterally on the tibia for about two thirds of the length of that bone, it passes on the foreside under the common annular ligament, and extensor pollicis, to the articulation of the foot; giving off several rami both to the right and left hand, which communicate la-

terally with the tibialis posterior and peronæa posterior, so that these two bones are in a manner surrounded by arteries.

At the joint of the foot, it sends out branches which run between the astragalus and os calcis, being distributed to the articulation and to the bones of the tarsus.

Having passed the fold of the foot, it sends off, toward both sides, other rami, which communicate with the posterior tibialis and peronæa; all these branches making a kind of circles round the tarsus.

Afterwards the anterior tibial artery advances on the convex side of the foot, as far as the interstice between the first and second metatarsal bones; between the heads of which it sends a large branch, which perforates the superior interosseous muscles, and, joining the tibialis posterior, forms an arch on the side of the foot.

It likewise sends two or three considerable branches over the other metatarsal bones, which go to the rest of the interosseous muscles, integuments, &c. and communicate with each other.

Lastly, This artery terminates by two principal branches, one of which goes to the thenar and inside of the great toe; the other is spent upon the outside of the great toe, and the inside of the second toe.

The tibialis posterior, called likewise suralis, runs down between the solei, tibialis posticus, flexor digitorum communis, and flexor pollicis; giving branches to these muscles, to the tibia, and to the marrow of that bone, through a particular canal in its posterior and upper part.

Afterwards it runs behind the inner ankle, communicating with the tibialis anterior, and surrounded by the neighbouring veins; and passes to the sole of the foot between the concave side of the os calcis and thenar muscle, where it divides into two branches, one large or external, the other small or internal.

The great branch, or arteria plantaris externa, passes on the concave side of the os calcis obliquely under the sole of the foot, to the basis of the fifth metatarsal bone, and from thence runs in a kind of arch toward the great toe, communicating there with the tibialis anterior, which perforates the interosseous muscles.

The convex side of this arch supplies both sides of the last three toes, and the outside of the second toe, forming small communicating arches as in the hand.

The small branch, or arteria plantaris interna, having reached beyond the middle of the sole of the foot, is divided into two; one of which goes to the great toe, communicating with the ramus of the tibialis anterior; the other is distributed to the first phalanges of the other toes, communicating with the ramifications from the arch already mentioned.

The arteria peronæa runs down on the backside of the fibula, between the soleus and flexor pollicis, to which, and to the neighbouring parts, it gives rami in its passage.

Having reached to the lower third part of the fibula, it sends off a considerable branch, which runs in between the tibia and that bone, passing between their extremities from behind forward, below the interosseous ligament, and is distributed to the integuments of the tarsus.

Lastly,

Lastly, the peronea continuing its course downward, on the backside of the fibula, as far as the os calcis, forms an arch with the tibialis posterior, between the astragalus and the tendo-achillis.

From thence it runs outward, and a little above the outer ankle communicates with the tibialis anterior by an arch, which sends several small ramifications to the neighbouring parts.

P A R T IV.

O F T H E V E I N S.

THE blood, distributed to all parts of the body by two kinds of arteries, the aorta and arteria pulmonaris, returns by three kinds of veins, called by anatomists vena cava, vena portæ, and vena pulmonaris.

The vena cava carries back to the right auricle of the heart, the blood conveyed by the aorta to all parts of the body except what goes by the arteriæ coronariæ cordis. It receives all this blood from the arterial ramifications in part directly, and in part indirectly.

The vena portæ receives the blood carried to the floating viscera of the abdomen by the arteria cæliaca and the two mesentericæ, and conveys it to the vena hepatica, and from thence to the vena cava.

The vena pulmonaris conveys to the pulmonary sinus, or left auricle of the heart, the blood carried to the lungs by the arteria pulmonaris.

We commonly talk of the vena cava in general, as if it were but one vein at its origin, or had but one common trunk; whereas it goes out from the right auricle of the heart by two large separate trunks, in a direction almost perpendicularly opposite to each other, one running upward, called vena cava superior; the other downward, called vena cava inferior.

The vena cava superior is distributed chiefly to the thorax, head, and upper extremities, and but very little to the parts below the diaphragm.

The vena cava inferior is distributed chiefly to the abdomen and lower extremities, and but very little to the parts above the diaphragm.

The trunk of each of these two veins sends off, much in the same manner with the arteries, a certain number of principal or capital branches, which are afterwards ramified in different manners. Each trunk terminates afterwards by a bifurcation or a division into two subordinate trunks, each of which gives off other principal branches, ending in a great number of small trunks, rami, and ramifications.

The superior vena cava runs up from the right auricle of the heart, almost in a direct course, for about two fingers breadth, lying within the pericardium, in the right side of the trunk of the aorta, but a little more anteriorly.

As it goes out of the pericardium, it is inclined a little to the left hand, and then runs up as high as the cartilage of the first true rib, and a little higher than the

curvature of the aorta. At this place it terminates by a bifurcation or division into two large branches or subordinate trunks, one of which runs toward the left hand, the other toward the right.

These two branches are named subclaviæ, as lying behind the claviculæ.

The trunk of the superior cava, from where it leaves the pericardium to the bifurcation, sends out anteriorly several small branches. These branches are the vena mediastina, pericardia, diaphragmatica superior, thymica, mammaria interna, and trachealis.

All these small branches from the trunk of the cava superior are termed dextræ; and their fellows on the other side, called sinistræ, do not arise from the trunk, but from the left subclavia.

Posteriorly, a little above the pericardium, the trunk of the superior cava sends out a capital branch, called vena azygos, or vena sine parti, which runs down on the right side of the bodies of the vertebræ dorsi, almost to the diaphragm; giving off the greatest part of the venæ intercostales and lumbaris superiores.

The two subclaviæ run laterally or toward each side, and terminate as they go out of the thorax, between the first rib and clavicula.

The right subclavian, which is the shortest of the two, commonly sends out four capital branches; the jugularis externa, jugularis interna, vertebralis, and axillaris.

The left subclavian being longer than the right, gives off, first of all, the small veins on the left side, answering those on the right side that come from the trunk of the superior cava, viz. the mediastina, pericardia, diaphragmatica superior, thymica, mammaria interna, and trachealis.

Next to these small veins, called sinistræ, it detaches another small branch, called intercostalis superior sinistra, and then four large branches like those from the right subclavian, viz. the jugularis externa, jugularis interna, vertebralis, and axillaris, which are termed sinistræ.

The external jugular veins are distributed chiefly to the outer parts of the throat, neck and head; and send a small vein to the arm, named cephalica, which assists in forming a large one of the same name.

The internal jugular veins go to the internal parts of the neck and head, communicating with the sinuses of the

the dura mater, and in several places with the external jugular veins.

The vertebral veins pass through the holes in the transverse apophyses of the vertebrae of the neck, sending branches to the neck and occiput. They form the sinus venales of these vertebrae, and communicate with the sinuses of the dura mater.

The axillary veins are continuations of the subclavia, from where these leave the thorax, to the axilla. They produce the mammaria internæ, thoracice, scapulares or humerales, and a branch to each arm, which, together with that from the external jugularis, forms the vena cephalica.

Afterwards the axillary vein terminates in the principal vein of the arm, called basilica; which, together with the cephalica, is distributed by numerous ramifications to all parts of the arm, fore-arm, and hand.

The portion of the inferior vena cava contained in the pericardium is very small, being scarcely the twelfth part of an inch on the fore-part, and not above a quarter of an inch on the back part. From thence it immediately perforates the diaphragm, to which it gives the venæ diaphragmaticæ inferiores or phrenicæ.

It passes next behind the liver, through the great sinus of that viscus, to which it furnishes several branches, termed venæ hepaticæ.

In this course it inclines a little toward the spina dorsi and aorta inferior, the trunk and ramifications of which it afterwards accompanies in the abdomen, all the way to the os sacrum.

Thus the inferior cava sends out on each side, in the same manner with the aorta, the venæ adiposæ, renales, spermaticæ, lumbares, and sacrae. Having reached to the os sacrum, it loses the name of cava, and terminating by a bifurcation, like that of the descending aorta, it forms the two venæ iliacæ.

These iliac veins having given off the hypogastricæ, with all their ramifications, to the viscera of the pelvis, and to some other external and internal neighbouring parts, go out of the abdomen, under the ligamentum Fallopii, and there take the name of venæ crurales.

Each crural vein sends off numerous ramifications to all the lower extremity.

The vena azygos or sine pari is very considerable, and arises posteriorly from the superior cava a little above the pericardium.

It is immediately afterwards bent backward over the origin of the right lung, forming an arch which surrounds the great pulmonary vessels on that side.

From thence it runs down on the right side of the vertebrae dorsi on one side of the aorta, and before the intercostal arteries; and getting behind the diaphragm, it terminates by a very sensible anastomosis, sometimes with the vena renalis, sometimes with a neighbouring lumbar vein, and sometimes immediately with the trunk of the cava inferior.

The vena azygos sends out two or three small veins from the top of the arch, one of which goes to the aspera arteria; the others partly to the aspera arteria, and partly to the bronchia, by the name of venæ

bronchiales, accompanying the ramifications of the bronchial artery.

Afterwards the azygos detaches from the extremity of the arch a small trunk common to two or three small veins, called intercostales superiores dextræ, which bring back the blood from the first three series of intercostal muscles, and from the neighbouring part of the pleura.

These intercostal veins send branches through the intercostal muscles to the serratus superior pollicis, serratus major, &c. and afterwards they run along the interstices between the ribs, communicating with the venæ mammariae.

They likewise send small branches backward to the vertebral muscles and canal of the spine, where they communicate with the venal circles, or sinuses which bring back the blood from the medulla spinalis.

As the azygos runs down, it sends off the inferior intercostal veins on the right side, one going to each series of intercostal muscles. These veins run along the lower edges of the ribs, and perforate the muscles by branches, which go to the posterior and external part of the thorax.

They communicate with the venæ thoracice, and most commonly with the mammaria interna; and lastly, more or less with each other, by perpendicular branches, near the posterior extremities of the ribs.

The azygos sends off likewise the left intercostal veins, but seldom the whole number; for the superior veins come often from the left subclavian. The inferior intercostal veins, to the number of six or seven, come often from the trunk of the azygos; and running between the aorta and vertebrae, they send off almost the same ramifications with the veins on the right side, and likewise some to the œsophagus.

The azygos, having reached below the last rib, sends off a large branch, which bending outward, perforates the muscles of the abdomen, is ramified between their different planes, and communicates with the like ramifications of the last or last two intercostal veins.

The pectorales internæ, are small veins disposed in pairs toward the right and left hand, behind the sternum and parts near it, including the diaphragmaticæ superiores, or pericardio-diaphragmaticæ, mediastinæ, mammariae internæ, thymicæ, pericardii, and gutturales or tracheales.

The right vena mediastina goes out anteriorly from the trunk of the superior cava, a little above the origin of the azygos; the left comes from the subclavia.

The right superior diaphragmatica, or pericardio-diaphragmatica, comes anteriorly from the root of the bifurcation near the mediastina; and is distributed, by several branches, to the upper, fore, and back parts of the pericardium, communicating with those of the left diaphragmatica. The left superior diaphragmatica comes from the left subclavian, a little below the origin of the mammaria.

The right internal mammaria arises anteriorly from the vena cava, a little below the angle of the bifurcation. It runs along the nearest internal or posterior edge of the sternum, and on the cartilaginous extremities of the

the right ribs, together with the artery of the same name. Having reached near the diaphragm, it sends it a branch which runs toward the tendinous plane, and communicates with the common diaphragmatic veins.

Afterwards this mammary vein gives small branches to the mediastinum, and others between the ribs to the integuments; of which those that pass between and under the cartilages of the last true ribs, run down on the inner or posterior side of the musculi recti abdominis, being ramified among their fleshy fibres, and communicating with the epigastric veins by several small twigs.

The left internal mammary arises anteriorly from the left subclavian, opposite to the cartilage or anterior extremity of the first true rib.

The right vena thymica, when it arises separately, goes out from the bifurcation; and when it is wanting, the thymus, from whence it takes its name, is furnished by the gutturalis, or some other neighbouring vein. This vein often reaches no lower than the inferior part of the thymus; and the left vein of the same name comes from the left subclavian, almost opposite to the sternum.

The right pericardium seems to go out rather from the origin of the right subclavian, than from the trunk of the superior cava. It goes to the upper side of the pericardium, and other neighbouring parts.

The right gutturalis or trachealis goes out from the upper part of the bifurcation, above the mammary of the same side, sometimes more backward, and sometimes from the subclavia. It is distributed to the glandulæ thyroïdæ, trachea arteria, musculi sterno-hyoidæ, thymus, and glandulæ bronchiales. It communicates, by lateral branches, with the internal jugular vein. The left gutturalis comes from the upper or posterior part of the left subclavian, near its origin.

The right subclavian vein is very short, and its course very oblique, so that it appears to rise higher than the left vein. It sends off, first of all, four large branches, viz. the vertebralis, which is the first and most posterior; the jugularis interna, jugularis externa, and axillaris.

The left subclavian seems to ascend but very little after the bifurcation; and, in this course, it covers the origin of three large arteries, which come from the curvature of the aorta. It sends off four large branches, besides the small pectoral veins, and receives the ductus thoracicus.

It likewise gives off, before its principal division, a small trunk for the left superior intercostals, and this intercostal trunk furnishes likewise the left bronchialis.

Each subclavian vein, near the middle of the clavicle, sends off a branch, called cephalica, which descends near the surface of the body, between the deltoïdes and pectoralis major.

Each external jugular vein arises from the subclavian on the same side, sometimes from the axillaris, and sometimes from the union of these two veins. They run up between the musculus cutaneus and sterno-mastoïdeus.

Sometimes they are double from their very origins; and when they are single, each of them divides afterwards into two, one anterior, and the other posterior, or rather superior. The anterior vein goes to the throat

and face, running up toward the angle of the lower jaw, and the posterior goes to the temples and occiput.

The anterior external jugular vein is often a branch of the jugularis interna, and sometimes it comes from the vena axillaris.

It runs up toward the lateral part of the lower jaw, between the angle and the chin, and sends several branches forwards, backwards, and inwards.

Posteriorly it gives, (1.) A large branch on the side of the upper part of the larynx, which communicates with the jugularis interna, and likewise with a large short branch of the jugularis externa posterior. (2.) A small branch, which has the same communication, but which is not always to be found. (3.) Another small branch a little below the lower jaw, which communicates with the jugularis externa posterior.

Anteriorly it sends several branches to the muscles of the larynx, sterno-hyoidæ, thyro-hyoidæ, and to the integuments; and below the larynx it sends communicating branches to the jugularis externa anterior of the other side.

A little higher, opposite to the cartilago-thyroïdes, it gives off a transverse branch, which runs on the anterior and lower part of the musculi sterno-mastoïdæ, and communicates with the jugularis of the other side.

The superior and inferior transverse branches communicate on each side by branches more or less perpendicular, and send a small branch to the musculus quadratus of the chin, to the musculus cutaneus and integuments.

It sends another large branch anteriorly toward the symphysis of the lower jaw, which, after having supplied the maxillary glands, is distributed to the digastric muscle, to the chin and under lip.

Interiorly, at the same place, it sends out a large branch, which furnishes the glandulæ sublinguales, runs down toward the cornua of the os hyoides, to communicate with some branches of the jugularis interna, and sends several rami to the tongue, called vena ranina. It gives off likewise a small branch, which running upon the musculus labiorum triangularis, to the commissure of the lips, is distributed to the neighbouring parts.

The same branch which gives out the vena ranina, detaches another to the lateral parts of the septum palati, which is distributed to the amygdalæ, and to the uvula, and sends rami forward to the membrane which lines the arch of the palate. Another branch goes out from it to the pterygoïdeus internus, peristaphylini, and cephalo-pharyngei.

Afterwards the trunk of the anterior external jugular vein runs up on the musculus triangularis, where it receives the name of vena triangularis, in a winding course from the angle of the lower jaw to the great or internal angle of the orbit, sending branches on each side to the muscles and integuments.

The trunk of the vena angularis having reached the bones of the nose, sends out a branch through the lateral cartilages of the nose, which is distributed to the nares; and another which runs down in a winding course to the upper lip.

At the great or inner angle of the eye, the same trunk sends off several other branches; the first of which goes

to the root of the nose, and communicating with its fellow from the other side, gives several small veins to the holes of the ossa nasi.

The second branch runs up on the fore-head, by the name of vena frontalis, and is distributed to each side.

The third branch enters the orbit in a winding course, on one side of the cartilaginous pulley, and communicates with the sinuses of the dura mater, by the orbitary sinus of the eye.

The fourth branch goes along the musculus superficialis and the upper part of the orbicularis, to the small or external angle of the eye, to communicate with the vena temporalis, and with that vein which runs along the lower part of the orbicularis muscle.

The posterior or superior external jugular vein runs up toward the parotid gland, and lower anterior part of the eye, giving out several branches toward each side.

At its origin it sends out posteriorly, a principal branch, with its ramifications, to the muscles which cover the scapula and joint of the humerus, commonly called vena muscularis.

A little higher, it gives off the vena cervicalis, which goes to the vertebral muscles of the neck.

Near the cervical vein, but a little more outward, it gives off sometimes the small vena cephalica, which runs down between the pectoralis major and deltoides, and unites with the vena cephalica of the arm.

Backward it detaches the vena occipitalis, which is distributed on the occiput; it likewise sends out a small vein, which enters the cranium by the posterior mastoid hole, and terminates in one of the lateral sinuses of the dura mater.

Having reached as far as the parotid gland, it forms communications with the anterior external jugular, under the angle of the lower jaw; and then passes through the parotid gland, between that angle and the condyle, giving off a large branch which communicates with another branch common to the internal and anterior external jugulars.

Afterwards it passes before the ear, taking the name of vena temporalis, which is distributed to the temples and lateral parts of the head, towards the occiput and fore-head.

The temporal vein of one side communicates, above, with its fellow on the other side; before, with the vena frontalis; and behind, with the vena occipitalis. Opposite to the ear, it gives out a large branch, one ramus of which runs under the lower edge of the zygoma, and then returning, communicates with another ramus from the same jugularis, a little below the condyle of the lower jaw.

Behind this condyle, it gives branches to the temporal muscle, to the neighbouring parts of the upper jaw, and to the inside of the lower jaw.

The internal jugular vein is the largest of those that go to the head.

It runs up behind the sterno-mastoidæus and omo-hydroæus, which it crosses, along the sides of the vertebrae of the neck, by the edge of the longus colli, to the fossula of the foramen lacerum of the basis cranii.

The first branches which it sends off are small, and go

to the thyroid glands. About two fingers breadth higher up, it detaches a middle-sized branch, which runs laterally towards the larynx, and may be named vena gutturalis.

This guttural vein divides chiefly into three branches; the lowest of which goes to the thyroid gland and neighbouring muscles; the middle branch to the larynx, musculi thyroidei, &c. and the third runs upward to the great communication between the two jugulars.

About the same distance upward, almost opposite to the os hyoides, the internal jugular gives another branch, which sends rami to the muscles belonging to that bone, and others which communicate with the foregoing branch. This other branch runs upward toward the parotid gland and angle of the lower jaw, where it sends communicating branches forward and backward to the two external jugulars.

The internal jugular sends another branch backward, which is distributed to the occiput, where it communicates with a branch of the vertebralis, and, through the posterior mastoid hole, with the lateral sinus of the dura mater.

Afterwards it reaches the foramen lacerum of the basis cranii, bending a little, and sending off small twigs to the pharynx and neighbouring muscles.

The vertebral vein arises posteriorly from the subclavia or axillaris, sometimes by two stems.

The first and principal stem gives out a branch, called vena cervicalis, which is distributed to the neighbouring muscles, and afterwards runs up through the holes of the transverse apophyses of the vertebrae colli.

The other stem of the vertebral vein runs up on the side of the vertebrae; and having reached the fourth, or sometimes higher, it runs in between the transverse apophyses of that vertebra and the fifth, to join the first or principal stem.

Thus the vertebral vein accompanies the artery of the same name, sometimes in one trunk, sometimes in several stems, through all the holes of the transverse apophyses of the vertebrae colli, all the way to the great foramen occipitale, communicating with the occipital veins and small occipital sinuses of the dura mater.

In its passage it gives off one branch, which enters by the posterior condyloid hole of the os occipitis, and communicates with the lateral sinus of the dura mater.

As these veins run through the holes in the transverse apophyses, they send branches forward to the anterior muscles of the neck, and to the small anterior muscles of the head.

Other branches go likewise outward and backward to the musculi transversales and vertebrales colli; and inward to the great canal of the spinal marrow, where they form sinuses, which communicate with those on the other side.

These vertebral sinuses are pretty numerous, and placed one above another all the way to the occiput; the lower communicate with the upper; and at the great foramen of the os occipitis there is a communication between them and the occipital sinuses of the dura mater.

The subclavian vein having sent off the branches already described, goes out of the thorax, and passes before

fore the anterior portion of the musculus scalenus, and between the first rib and the clavicle, to the axilla. Through this course it takes the name of vena axillaris, and gives off several branches, the chief of which are the venæ musculares, thoracice, and vena cephalica.

The musculares, are distributed to the middle portion of the musculus trapezius, to the angularis, infra-spinatus, and subscapularis; and as some of these branches go to the shoulder exteriorly, others interiorly, the venæ scapulares are distinguished into external and internal.

A little before the axillaris reaches the axilla, it sends out the venæ thoracice, one of which is superior, called also mammaria externa, and the other inferior. It likewise sends rami to the musculus subscapularis, teres major, teres minor, supra-spinatus, latissimus dorsi, serratus major, pectoralis minor, pectoralis major, and to the glands of the axilla.

The axillaris having reached the side of the head of the os humeri, produces a branch, named vena cephalica, and afterwards runs along the arm by the name of vena basilica.

The cephalic vein, which is a branch of the axillaris, at a small distance from its origin, joins the small cephalica, which runs down from the subclavia, or jugularis externa.

The great cephalica runs down between the tendons of the last mentioned muscles, and along the outer edge of the external portion of the biceps; communicating several times with the vena basilica, and sending small rami on each side, to the neighbouring muscles, fat and skin.

A little below the external condyle of the os humeri, it detaches a branch backward, which runs up between the musculus brachialis and the upper portion of the supinator longus, and afterwards bends back between the os humeri and anconeus externus, where it communicates with some branches of the basilica.

Having reached very near the fold of the arm, it is divided into two principal branches, one long, the other short. The long branch is named radialis externa, and the short one may be called mediana cephalica, to distinguish it from another mediana, which is a short branch of the basilica.

The external radial vein runs along the radius between the muscles and integuments, giving off branches towards both sides, which communicate with other branches of the same vein, and with some from the basilica.

The mediana cephalica runs down obliquely toward the middle of the fold of the arm, under the integuments, and over the tendon of the biceps, where it joins a short branch of the same kind from the basilica.

From this anastomosis, a considerable branch goes out, which runs down on the fore-arm, uniting on one side with the vena cephalica, and communicating on the other with the basilica, by several irregular areolæ. The name of mediana is given to this large branch, as well as to the two short ones, by the union of which it is formed.

From this union of the two lateral medianæ, and sometimes from the origin of the mediana media, a branch goes out, which runs down on the inside of the

fore-arm, opposite to the interosseous ligament, and is called vena cubiti profunda. It goes to the neighbouring muscles, and communicates with the other veins of the fore-arm. The mediana cephalica sometimes sends down a long branch, called radialis interna, which lies almost parallel to the radialis externa.

Afterwards the cephalica, having reached the extremity of the radius, is distributed, by numerous areolæ, almost in the same course with the radial artery.

A particular branch goes out from it, which runs more or less superficially between the thumb and metacarpus, by the name of cephalica pollicis. The areolæ furnish the interosseous muscles and integuments, and communicate with a small ramus from the basilica, called by the ancients Salvatella.

The basilic vein sends off first of all, under the head of the os humeri, a pretty large branch, which passes almost transversely round the neck of that bone, from within backward, and from behind outward, running upon the scapula, where it is ramified on the deltoides, and communicates with the venæ scapulares externæ. This branch may be named vena sub-humeralis, or articularis.

This articular vein sends down two principal branches, one of which runs along the inside of the bone, to which, and to the periosteum, it gives small veins. The other turns forward, toward the middle of the arm between the bone and the biceps, and communicates with the cephalica.

Below the neck of the os humeri, near the hollow of the axilla, and behind the tendon of the pectoralis major, the basilica sends out a considerable branch, which runs down on the side of the brachial artery, and furnishes the neighbouring muscles on both sides. This vein is named profunda brachii.

Immediately afterwards, the basilica detaches two or three small veins, which run down very closely joined to the brachial artery, surrounding it at different distances by small twigs which communicate with each other.

These small veins, which often arise from the profunda superior, communicate with the basilica and cephalica; and having reached the fold of the arm, they divide like the artery; and the same divisions are continued along the whole fore-arm.

Afterwards the basilica continues its course along the inside of the os humeri, between the muscles and integuments, forming many communications with the vena profunda and cephalica, and supplying the muscles and integuments.

Having reached the inner condyle, and having sent off obliquely, in the fold of the arm, the mediana basilica, it runs along the ulna, between the integuments and muscles, a little toward the outside, by the name of cubitalis externa.

The basilica having at length reached the extremity of the ulna, sends several branches to the convex side of the carpus; one of which, named Salvatella, goes to that side of the little finger next the ring finger, having first communicated with the cephalica, by means of the venal areolæ conspicuous on the back of the hand. In the other fingers this vein follows nearly the same course with the arteries.

In general, the external or superficial veins of the forearm are larger than the internal.

The inferior VENA CAVA having run down about a quarter of an inch from the right auricle of the heart, within the pericardium, pierces that membrane and the tendinous portion of the diaphragm.

At this place it gives off the venæ diaphragmaticæ, or phrenicæ, which are distributed to the diaphragm, and appear chiefly on its lower side, one towards the right hand, and one towards the left. The right vein is more backward and lower than the left. The left is distributed partly to the pericardium, and partly to the diaphragm; and sometimes they send rami to the capsulæ renales.

The inferior cava having perforated the diaphragm, passes through the posterior part of the great fissure of the liver, penetrating a little into the substance of that viscus, between the great lobe and the lobulus Spigelii.

In its passage, it sends off commonly three large branches, called venæ hepaticæ, which are ramified in the liver.

Besides these large branches, it sends out some other small ones, either before or immediately after it goes out of the liver.

In the foetus, as the vena cava passes by the liver, it gives off the ductus venosus, which communicates with the sinus of the vena portæ; and in adults is changed to a flat ligament.

After its passage through the liver, the vena cava turns from before backward, and from right to left, toward the spina dorsi, placing itself on the right side of the aorta, which it accompanies from thence downward.

Having got as low as the arteriæ renales, it gives off the veins of the same name, termed formerly venæ emulgentes.

The right renal runs down a little obliquely, because of the situation of the kidney. The left vein crosses on the foreside of the trunk of the aorta, immediately above the superior mesenteric artery.

They send up the venæ capsulares, which go to the glandulæ renales, and downward; the venæ adiposæ, which go to the fatty covering of the kidneys; and ordinarily the left renal vein furnishes the left spermatic vein. Afterwards they run to the sinus, or cavity of the kidneys, in the substance of which they are distributed by numerous ramifications.

A little below the renal veins, the trunk of the cava sends out anteriorly, toward the right side, the right vena spermatica. The left spermatic vein comes commonly from the left renalis.

In their passage, they send several small branches on each side, to the peritoneum and mesentery, where they seem to be joined by anastomoses with the venæ mesaraicæ.

The cava sends likewise off posteriorly the venæ lumbaris, which commonly arise in pairs. These may be divided into superior and inferior veins.

Their origins vary in different manners. Sometimes the cava gives off a branch to each side below the first vertebra of the loins, which, like a common trunk, furnishes the lumbar veins. This branch communicates with the azygos.

Sometimes a considerable branch goes out from the lower extremity of the cava, near the bifurcation, chiefly on the right side, which afterwards running up between the bodies and transverse apophyses of the vertebrae, detaches the venæ lumbaris, and communicates with the azygos.

Sometimes a like branch comes from the beginning of the left vena iliacæ, and, running up on that side in the same manner, produces the lumbaris.

The venæ lumbaris on one side communicate by transverse branches with those of the other side, and likewise with each other by branches more or less longitudinal. The first and second often go from the azygos, and thereby they communicate with the intercostal veins.

The lumbar veins send small capillaries, in their passage, to the substance of the bodies of the vertebrae; and they are distributed to the muscles of the abdomen, quadratus lumborum, psoas, iliacus, &c. They send branches backward to the neighbouring vertebral muscles, and to the canal of the spine, and communicate with the venal sinuses.

The inferior cava, having reached as low as the last vertebra of the loins, and near the bifurcation of the aorta, runs in behind the right iliac artery, and there is divided into two subaltern trunks, called the right and left iliac veins.

From this bifurcation of the vena cava, the vena sacra goes out, and accompanies the artery of the same name in its distribution to the os sacrum, to the nerves which lie there, and to the membranes which cover both sides of that bone.

Each original iliac vein is divided on the side of the os sacrum, much after the same manner as the arteries, into two large trunks.

One of these trunks is named vena iliacæ externa or anterior; the other interna or posterior.

These veins follow nearly the course and distribution of the iliac arteries, except that the hypogastric vein does not send off the vena umbilicalis.

From the common trunk of the iliac veins, and sometimes from the origin of the iliacæ externa, a particular branch goes out, which is distributed to the musculus psoas, iliacus, and quadratus lumborum; and afterwards sends a ramus on the fore-side of the last transverse apophysis of the loins, to communicate with the last lumbar vein.

The external iliac, a little before it leaves the abdomen, near the ligamentum Fallopii, lying on the psoas and iliac muscles, gives off almost the same branches with the artery of the same name, and follows the same course. The chief branches are these:

A little before it goes out of the abdomen, it sends off from the outside, a small branch, which runs up along the crista of the os ilium, and gives branches on each side to the lateral and posterior lower portions of the musculi abdominis, to the musculus iliacus, &c.

From the inside, before it leaves the abdomen, it sends off the vena epigastrica; which having furnished some small rami to the neighbouring conglobated glands, runs up along the inside of the musculi recti, on which it is ramified both ways.

Afterwards

Afterwards the vena epigastrica runs upward, and joins the ramifications of the mammaria.

Before the iliac vein gets from under the ligamentum Fallopii, it sends several small rami to the neighbouring lymphatic glands; and immediately afterwards, losing the name of iliac, it takes that of cruralis.

The hypogastric, or internal iliac vein, runs behind the iliac artery, from which the following branches go out.

From the posterior or convex part of the arch, it gives a branch to the superior lateral part of the os sacrum, which is distributed to the musculus facer, or transversospinalis lumborum, and other muscles thereabouts, and to the cavity of the bone, which it enters through the first great hole.

A little lower, on the same side, it sends out another, which is distributed much in the same manner with the former, and enters the second hole.

From the external lateral part of the same arch, a little anteriorly, it sends out a large branch, which runs behind the great sciatic sinus, and is distributed to the musculi glutei, pyriformis, and gemelli.

Lower down, the same lateral part of the hypogastric vein gives out another large branch, called obturatrix; which, having run a little way, detaches several rami, and afterwards reaching the foramen ovale of the os innominatum, perforates the obturator muscles, communicates with the vena cruralis, and is distributed to the musculus pectineus, triceps, and neighbouring parts.

Among the branches sent off by the vena obturatrix, before it perforates the muscles, one is situated exteriorly, which runs toward the sciatic sinus, to the musculus iliacus, the superior part of the obturator internus, and to the os ilium.

Interiorly, the same obturator vein sends off another branch, which is distributed to the ureters, bladder, and internal parts of generation in both sexes.

Lastly, the hypogastric vein runs backward, and goes out of the pelvis, above the ligament which lies between the inferior lateral part of the os sacrum and spine of the ischium.

It next sends a large branch upward to the lower part of the os sacrum, and two or more downward; which, running behind the same ligament, are distributed to the buttocks, anus, neighbouring portion of the musculus pectineus, and to the external parts of generation.

The veins that go to the anus, are termed hemorrhoidales externe; they that go to the parts of generation, pudice interne. The external hemorrhoidales communicate with the internal veins of the same name, which come from the small vena mesaraica.

The crural vein goes out under the ligamentum Fallopii, on the inside of the crural artery, and immediately gives small branches to the inguinal glands, the musculus pectineus, and parts of generation. These last are termed pudice externe, and evidently communicate with the internal veins of the same name.

About an inch below, where it leaves the abdomen, the crural vein produces a large branch, which runs down anteriorly between the integuments and the sartorius,

following the direction of that muscle almost all the way to the inside of the thigh.

This branch having afterwards got beyond the condyles of the os femoris, runs down between the integuments and inner angle of the tibia, to the fore-part of the inner ankle, and is distributed to the foot. All this large branch is named vena saphena, or saphena major.

After the origin of the saphena, as the trunk of the crural veins runs down, it sinks in between the muscles, and is distributed to all the inner or deep parts of the lower extremity, accompanying the crural artery to the very extremity of the foot.

As the saphena is a vein of very large extent, we shall here describe it altogether, and afterwards return to the vena cruralis.

The vena saphena, in its passage from the inguen to the foot, is covered only by the skin and fat. Immediately after its rise, it gives small veins to the inferior inguinal glands; and then it gives out others more anteriorly, which, running under the integuments, communicate with each other by numerous areolæ.

The saphena, having run down on the thigh, as low as the middle of the sartorius, sends off to the same side several branches, which communicate with each other, and with the superior branches.

Between these upper and lower branches, the saphena sends backward a particular branch; which, after being distributed to the integuments which cover the gracilis internus and triceps, turns backward; and a little below the ham, runs in among the muscles situated there, and communicates with another branch, which may be termed saphena minor.

Afterwards the trunk of the great saphena runs down on the inside of the tibia, lying always near the skin; and at the upper part of that bone it sends branches forward, outward, and backward.

The anterior branches go to the integuments on the upper part of the leg; the posterior, to those which cover the gastrocnemii, and communicate with the little saphena; and the external branches are likewise distributed to the fat and integuments, and having reached as low as the middle of the tibia, it sends a communicating branch to the trunk of the great saphena.

From this communication, a branch goes out anteriorly, which runs along the integuments of the tibia all the way to the outer ankle.

As the saphena runs down on the inside of the tibia, it sends out a branch near the middle of that bone, which runs up behind the tendons of the sartorius, gracilis internus, and semi-nervosus, then between the tibia and upper end of the soleus, and is joined by an anastomosis with the crural vein.

At the lower part of the tibia, the saphena produces a considerable branch, which runs obliquely forward over the joint of the tarsus toward the outer ankle, sending off several rami which communicate with each other, and with the trunk of the saphena.

The extremity of this trunk passes on the foreside of the inner ankle, and runs irregularly under the skin, along

long the interspace between the first two metatarsal bones toward the great toe, where this vein terminates.

The crural vein, having sent off the saphena, and the small branches for the pectineus, &c. as has been said, runs down on the thigh behind the crural artery. Opposite to the little trochanter, it produces two large short branches, or one which afterwards divides into two, whereof one is anterior, the other posterior.

The anterior branch runs more or less transversely forward, to be distributed to the vastus internus, lower part of the pectineus, and of the second triceps, and to the other two muscles of the same name, running in between them as it goes from one to another.

The posterior branch runs more or less transversely backward, and furnishes the glutei, vastus externus, and beginning of the biceps.

A little below these two branches, about the upper extremity of the vastus internus, the crural vein produces a branch which runs down on the side of the trunk, covering the crural artery, almost as low as the ham, where it is again united to the trunk by an anastomosis. It has the name of vena sciatica, from the sciatic nerve which it accompanies.

On the outside of this anastomosis, the crural vein gives off a branch which runs backward between the biceps and neighbouring muscles, and so downward on the backside of the leg a little exteriorly, and very near the skin, all the way to the outer ankle. This vein is termed saphena minor, or externa.

The little saphena, having got near the integuments in its course downward, gives out a branch which runs backward, and communicates with the great saphena about the middle of the backside of the thigh.

Immediately above and below the ham, this vein sends out other branches, which likewise communicate with the saphena major, and, having run down about one third part of the backside of the tibia, it sends off another branch, which is afterwards re-united to the trunk.

About the beginning of the tendo-achillis, the little saphena runs outward in the integuments, toward the outer ankles, where it terminates in cutaneous ramifications sent to every side.

The crural vein, having detached the little saphena, runs down between the biceps and the other flexors of the leg, closely accompanied by the crural artery, between which and the inner condyle of the os femoris it is situated.

A little above the ham, it takes the name of vena poplitea; and as it runs down betwixt the two condyles, it gives branches to the flexor muscles, to the lower and posterior parts of both vasti, and to the fat which lies above the interspace of the two condyles.

It likewise gives off several other branches, one of which runs up laterally between the outer condyle and the biceps, and then turning forward, is ramified in the same manner with the artery.

The vena poplitea runs down immediately behind the muscle of the same name, at the lower part of which it sends off several ramifications to each side, which divide and unite again in different ways; and afterwards it loses its name, being divided into three considerable

branches, called tibialis anterior, tibialis posterior, and peronea.

The anterior tibial vein, having distributed some small branches from its very beginning to the muscles behind the heads of the two bones of the leg, perforates the interosseous ligament from behind, forward, and runs between the superior portions of the musculus tibialis anticus, and extensor digitorum communis.

As soon as it pierces the interosseous ligament, it distributes small superficial branches to the head of the tibia and fibula, which run to the joint of the knee, and communicate with the lateral branches of the vena poplitea.

Afterwards it divides into two or three branches, which run down together on the foreside of the interosseous ligament in company with the anterior tibial artery, which they surround at different distances, by small communicating circles.

These branches having reached the lower extremity of the leg, unite in one, which afterwards divides into several, the ramifications of which are distributed to the foot.

The posterior tibial vein gives off, from its beginning, a branch toward the inside, which is distributed to the gastrocnemii and soleus. This vein is named suralis.

Afterwards the posterior tibialis runs down between the soleus and tibialis posticus, giving branches to each of them. It is divided in the same manner as the tibialis anterior, into two or three branches, which, as they run, surround the corresponding artery, by small communicating circles formed at different distances.

It continues this course in company with the artery as low as the outer ankle, furnishing the musculus tibialis posticus, and the long flexors of the toes.

Lastly, it passes on the inside of the os calcis, under the sole of the foot, where it forms the vena plantares, by dividing into several transverse arches, which communicate with each other, and with the saphena, and send ramifications to the toes.

The vena peronea is likewise double, and sometimes triple. It runs down on the inside of the fibula, which it likewise surrounds at different distances, by communicating branches, after the manner of the tibialis posterior.

It runs down as low as the outer ankle, communicating several times with the tibialis posterior, and sending ramifications to the neighbouring portions of the musculi peronæi, and long flexors of the toes.

The vena portæ is a large vein, the trunk of which is situated chiefly between the eminencies on the lower or concave side of the liver.

It may be considered as made up of two large veins, joined almost endwise by their trunks, from each of which the branches and ramifications go out in opposite directions. One of these trunks adheres to the liver, and is ramified in that viscus, its branches accompanying the whole distribution of the hepatic artery.

The other trunk is without the liver, and sends its branches to the viscera, supplied by the rest of the arteria cæliaca, and by the two mesentericæ, that is, to the stomach, intestines, pancreas, spleen, mesentery, and omentum.

The first portion of this vein may be termed vena portæ.

portæ hepatica, superior or minor, the trunk of which is commonly known by the name of sinus venæ portarum. The other portion may be called vena portæ ventralis, inferior or major.

The large trunk of the vena portæ inferior, or ventralis, is situated under the lower or concave side of the liver, and joined by an anastomosis to the sinus of the vena portæ hepatica, between the middle and right extremity of that sinus. From thence it runs down a little obliquely from right to left, behind or under the trunk of the arteria hepatica, bending behind the beginning of the duodenum, and under the head of the pancreas.

Having reached to the head of the pancreas, this trunk loses the general name of vena portæ, and terminates in three large principal branches, which are distributed, by numerous ramifications, to the viscera already named. The first branch is termed vena mesaraica, or mesaraica major; the second, splenica; and the third, hæmorrhoidalis interna, or mesaraica minor.

The vena mesaraica major appears to be a continuation of the trunk of the vena portæ inferior. The splenica is a capital branch of that trunk; and the hæmorrhoidalis interna has sometimes a common origin with the splenica.

The inferior vena portæ, before the formation of these three branches, sends off from the trunk several small rami, which are commonly the venæ cysticæ, hepatica minor, pylorica, duodenalis, and sometimes the gallica recta, and coronaria ventriculi.

All these small veins sometimes arise separately; and, in other subjects, some of them go out by small common trunks.

The cystic veins run along the vesicula fellis, from its neck to the bottom; and as they are often no more than two in number, they are called cysticæ gemellæ.

The small hepatic vein is commonly a branch of one of the cysticæ.

The vena pylorica arises from the great trunk, almost opposite to the origin of the cysticæ; and sometimes is only a branch of the right gallica. It passes over the pylorus to the short arch of the stomach, where it is joined, by anastomosis, with the coronaria ventriculi.

The duodenal vein, commonly called vena intestinalis, goes out from the great trunk near the cysticæ, and sometimes from the small common trunk of these veins. It is distributed chiefly to the intestinum duodenum, and sends likewise some rami to the pancreas.

The inferior vena portæ, having given off the splenica, changes its name to that of mesaraica, or mesaraica major; which often appears to be rather a continuation of the trunk, than of one of the great branches.

It bends toward the superior mesenteric artery, sending off two veins, and afterwards running up over that artery, it accompanies it in those portions of the mesentery and mesocolon which belong to the small intestine, the cæcum, and right portion of the colon.

The first particular branch from this trunk is called vena colica. It goes out from the anterior part of the trunk, before it joins the artery, and runs directly to the middle of the colon, where it divides to the right and left, and forms arches. On the left hand, it communicates

with the superior or ascending branch of the hæmorrhoidalis; and on the right, with the second branch of the mesaraica.

This second branch is a little under the first, or colica anterior, and something more towards the right hand. It may be named gastro-colica, and is soon divided into two branches, one superior, the other inferior.

The superior branch of the vena gastro-colica sends small veins to the head of the pancreas, and forms the vena gallica, or gastro-epiploica dextra, which goes from the pylorus to the great curvature of the stomach, and communicates with the gallica sinistra. In its passage it supplies the stomach and omentum, and communicates with the pylorica, coronaria ventriculi, &c.

The inferior branch of the vena gastro-colica, which may be called colica dextra, goes to the right portion of the colon; and from thence to the upper part of that intestine, where it is divided archwise, and communicates with the right branch of the colica anterior, and with a branch of the vena cæcalis.

The trunk of the great mesaraic vein sends out sometimes, opposite to the gallica, a particular branch to the omentum, called epiploica dextra. But almost immediately before it ascends over the mesenteric artery, it produces two large branches very near each other, which pass behind and under the artery, being distributed to the jejunum and part of the ilium by numerous ramifications.

Afterwards the trunk of the mesaraic passes over the superior mesenteric artery, to which it adheres very closely, and from the convex side of its arch sends out several branches, almost in the same manner with the artery.

From the concave side of the mesaraic vein, a little below the origin of the second branch, from the convex side, arises a branch, called vena cæcalis, which runs to the beginning of the colon, crossing one of the branches of the superior mesenteric artery.

This cæcal vein divides by two arches, the uppermost of which communicates with the lower branch of the vena gastro-colica; the other, after having sent ramifications to the intestinum cæcum and appendicula vermiculiformis, communicates below with the extremity of the great mesaraic vein.

The splenic vein is one of the three great branches of the vena portæ. It runs transversely from the right to the left, first under the duodenum, and then along the lower side of the pancreas.

In this course it gives off several veins, viz. the vena coronaria ventriculi, pancreatica, gallica, or gastro-epiploica sinistra, and epiploica sinistra. It likewise often gives origin to the hæmorrhoidalis interna, the third capital branch of the vena portæ.

It terminates afterwards by a winding course, being divided into several branches that go to the spleen; one of which produces the small veins called, by the ancients, vasa brevia.

The coronaria ventriculi runs along the small arch of that viscus toward the pylorus, where it joins and becomes continuous with the vena pylorica. In its passage, it gives several rami to the sides of the stomach.

The venæ pancreaticæ are several small branches

sent by the splenica to the pancreas, along its lower side.

The left gastric, or gastro-epiploic vein, goes out from the splenica, at the left extremity of the pancreas; from whence it runs to the great extremity of the stomach, and along the great arch, till it meets the gastrica dextra, which is continuous with the sinistra.

In its passage, it gives several branches to both sides of the stomach, which are distributed by numerous ramifications, form many areolæ, and communicate with the branches of the coronaria ventriculi.

At a small distance from its origin, this gastric vein sends out a branch, which is distributed to the omentum; and on this account it has been called gastrico-epiploica.

The vena epiploica sinistra arises at the small extremity of the pancreas, and is ramified on the omentum, all the way to the colon, where it communicates with the hæmorrhoidal interna.

Lastly, the vena splenica reaches the fissure of the spleen, which it enters through its whole length by several branches. It is from the most posterior of these branches that the veins are sent off to the great extremity of the stomach, formerly known by the name of vasa brevia, which communicate with the coronaria ventriculi and gastrica sinistra.

The internal hæmorrhoidal vein is one of the three great branches of the vena portæ, coming ordinarily from the beginning of the vena splenica, and sometimes from the extremity or angle of the bifurcation of the great trunk of the vena portæ.

At a small distance from its beginning, it gives to the duodenum a second vena duodenalis.

Afterwards it is divided into two branches, one superior or ascending, the other inferior or descending. The first runs to the upper part of the arch of the colon, where, after many ramifications, it communicates with a branch of the great mesærica, with the ramifications of the gastro-epiploica sinistra, and with those of the neighbouring epiploica.

The inferior branch runs down on the left portion of the colon, on the lower incurvations of that intestine, and on the rectum, all the way to the anus. In this course, it supplies the mesocolon, and forms arches, which send out numerous small ramifications, which surround these intestines.

This vein has been named hæmorrhoidal, from the tumours often found at its extremity next the anus, which are called hæmorrhoides. The word interna is added, to distinguish this vein from the hæmorrhoidal externa, which comes from the vena hypogastrica, and with which this vein communicates by capillary ramifications.

EXPLANATION OF PLATE XVII.

This plate represents the heart in situ, all the large arteries and veins, with some of the muscles, &c.

MUSCLES.—SUPERIOR EXTREMITY.—a, Masseter. b, Complexus. c, Diagastricus. d, Os hyoides. e, Thyroid gland. f, Levator scapule. g, Cucullaris. h h, The clavicles cut. i, The deltoid muscle. k, Biceps flexor cubiti cut. l, Coraco-brachialis. m, Triceps extensor cubiti. n, The heads of the pronator teres, flexor carpi radialis, and flexor digitorum sublimis, cut. o, The flexor carpi ulnaris, cut at its extremity. p, Flexor digitorum profundus. q, Supinator radii longus, cut at its extremity. r, Ligamentum carpi transversale. s, Extensors carpi radiales. t, Latissimus dorsi. u, Anterior edge of the serratus anticus major. v v, The inferior part of the diaphragm. w w, Its anterior edge cut. x x, The kidneys. y, Transversus abdominis. z, Os ilium.

INFERIOR EXTREMITY.—a, Psoas magnus. b, Iliacus internus. c, The fleshy origin of the tensor vagine femoris. d d, The ossa pubis cut from each other. e, Musculus pectineus cut from its origin. f, Short head of the triceps adductor femoris cut. g, The great head of the triceps. h, The long head cut. i, Vastus internus. k, Vastus externus. l, Crureus. m, Gemellus. n, Soleus. o, Tibia. p, Peroneus longus. q, Peroneus brevis. r, Fibula.

HEART and BLOOD-VESSELS.—A, The heart, with the coronary arteries and veins. B, The right auricle of the heart. C, The aorta ascendens. D, The left subclavian artery. E, The left carotid artery. F, The common trunk which sends off the

right subclavian and right carotid arteries. G, The carotis externa. H, Arteria facialis, which sends off the coronary arteries of the lips. I, Arteria temporalis profunda. K, Aorta descendens. L l, The iliac arteries,—which send off M m, The femoral or crural arteries. N. B. The other arteries in this figure have the same distribution as the veins of the same name:—And generally, in the anatomical plates, the description to be found on the one side, points out the same parts in the other. 1, The frontal vein. 2, The facial vein. 3, Vena temporalis profunda. 4, Vena occipitalis. 5, Vena jugularis externa. 6, Vena jugularis interna, covering the arteria carotis communis. 7, The vascular arch on the palm of the hand, which is formed by 8, the radial artery and vein, and 9, the ulnar artery and vein. 10 10, Cephalic vein. 11, Basilic vein, that on the right side, cut. 12, Median vein. 13, The humeral vein, which, with the median, covers the humeral artery. 14 14, The external thoracic, or mammary arteries and veins. 15, The axillary vein, covering the artery. 16 16, The subclavian veins, which, with (6 6) the jugulars, forms 17, the vena cava superior. 18, The cutaneous arch of veins on the fore-part of the foot. 19, The vena tibialis antica, covering the artery. 20, The vena profunda femoris, covering the artery. 21, The upper part of the vena saphena major. 22, The femoral vein. 23 23, The iliac veins. 24, 24, Vena cava inferior. 25 25, The renal veins covering the arteries. 26 26, The diaphragmatic veins.

THE medullary substance of the brain is employed in forming the white fibrous cords, which are called nerves. Within the skull we see the nerves to be the medullary substance continued; and the spinal marrow is all employed in forming nerves.

The nerves are composed of a great many threads, lying parallel to each other, or nearly so, at their exit from the medulla.

This fibrous texture is evident at the origin of most of the nerves within the skull; and in the cauda equina of the spinal marrow we can divide them into such small threads, that a very good eye can scarce perceive them; but these threads, when looked at with a microscope, appear each to be composed of a great number of smaller threads.

How small one of these fibrils of the nerves is, we know not; but when we consider that every, even the most minute part of the body is sensible, and that this must depend on the nerves, (which all conjoined would not make a cord of an inch diameter), being divided into branches or filaments to be dispersed through all these minute parts, we must be convinced, that the nervous fibrils are very small.

The medullary substance, of which the nervous fibrils are composed, is very tender, and would not be able to resist such forces as the nerves are exposed to within the bones, nor even the common force of the circulating fluids, were not the pia mater and tunica arachnoides continued upon them; the former giving them firmness and strength, and the latter furnishing a cellular coat to connect the threads of the nerves, to let them lie soft and moist, and to support the vessels which go with them.

It is this cellular substance that is distended when air is forced through a blow-pipe thrust into a nerve, and that makes a nerve appear all spongy, after being distended with air till it dries; the proper nervous fibrils shriveling so in drying, that they scarce can be observed.

These coats would not make the nerves strong enough to bear the stretching and pressure they are exposed to in their course to the different parts of the body; and therefore, where the nerves go out at the holes in the cranium and spine, the dura mater is generally wrapped closely round them, to collect their disgregated fibres into tight firm cords; and that the tension which they may happen to be exposed to may not injure them before they have got

this additional coat, it is firmly fixed to the sides of the holes in the bones through which they pass.

The nervous cords, thus composed of nervous fibrils, cellular coat, pia and dura mater, have such numerous blood-vessels, that, after their arteries only are injected, the whole cord is tinged of the colour of the injected liquor.

A nervous cord has very little elasticity, compared with several other parts of the body. When cut out of the body, it does not become observably shorter, while the blood-vessels contract three eighths of their length.

Nerves are generally lodged in a cellular or fatty substance, and have their course in the interstices of muscles, where they are guarded from pressure; but in several parts they are so placed, as if it was intended that they should there suffer the vibrating force of arteries, or the pressure of the contracting fibres of muscles.

The larger cords of the nerves divide into branches as they go off to the different parts; the branches being smaller than the trunk from which they come, and making generally an acute angle where they separate.

In several places, different nerves unite into one cord, which is commonly larger than any of the nerves which form it. Several nerves, particularly those which are distributed to the bowels, after such union, suddenly form a hard knot considerably larger than all the nerves of which it is made. These knots were formerly called corpora olivaria, and are now generally named ganglions.

The ganglions have thicker coats, more numerous and larger blood-vessels than the nerves; so that they appear more red and muscular.

Commonly numerous small nerves, which conjunctly are not equal to the size of the ganglion, are sent out from it, but with a structure no way different from that of other nerves.

The nerves sent to the organs of the senses, lose there their firm coats, and terminate in a pulpy substance. The optic nerves are expanded into the soft tender webs, the retinae. The auditory nerve has scarce the consistence of mucus in the vestibulum, cochlea, and semicircular canals of each ear. The papillae of the nose, tongue, and skin, are very soft.

The nerves of muscles can likewise be traced till they seem to lose their coats by becoming very soft; from which, and what we observed of the sensory nerves, there is reason to conclude, that the muscular nerves are also pulpy at their terminations, which we cannot indeed prosecute by dissection.

It is generally said, that there are forty pair of nerves in all; of which ten come out from the encephalon, and the other thirty have their origin from the spinal marrow.

Of the ten pair of nerves which come from the encephalon, the first is the OLFACTORY, which have their origin from the corpora striata, near the part where the internal carotid arteries are about to send off their branches to the different parts of the brain; and in their course under the anterior lobes of the brain, which have each a depression made for lodging them, become larger, till they are extended to the cribriform bone; where they split into a great number of small filaments, to pass through the little holes in that bone; and being joined by a branch of the fifth pair of nerves, are spread on the membrane of the nose.

The tender structure and sudden expansion of these nerves on such a large surface, render it impossible to trace them far; which has made some authors deny them to be nerves: But when we break the circumference of the cribriform lamella, and then gently raise it, we may see the distribution of the nerves some way on the membrane of the nose.

The contrivance of defending these long soft nerves from being too much pressed by the anterior lobes of the brain under which they lie, is singular; because they have not only the prominent orbital processes of the frontal bone to support the brain on each side, with the veins going into the longitudinal sinus, and other attachments bearing it up, but there is a groove formed in each lobe of the brain itself for them to lodge in. Their splitting into so many small branches before they enter the bones of the skull, is likewise peculiar to them; for generally the nerves come from the brain in disgregated filaments, and unite into cords, as they are going out at the holes of the bones. This contrivance is the best for answering the purpose they are designed for, of being the organ of smelling; for had they been expanded upon the membrane of the nose into a medullary web, such as the optic nerve forms, it would have been too sensible to bear the impressions of such objects as are applied to the nose; and a distribution in the more common way, of a cord sending off branches, would not have been equal enough for such an organ of sensation.

The second pair of nerves, the OPTIC, rising from the thalami nervorum opticorum, make a large curve outwards, and then run obliquely inwards and forwards, till they unite at the fore-part of the sella tureca; then soon divide, and each runs obliquely forwards and outwards to go out at its proper hole in the sphenoid bone, accompanied with the ocular artery, to be extended to the globe of the eye, within which each is expanded into a very fine cuplike web, that lines all the inside of the eye as far forwards as the ciliary circle, and is universally known by the name of RETINA.

Though the substance of this pair of nerves seems to be blended at the place where they are joined; yet observations of people whose optic nerves were not joined, and of others who were blind of one eye from a fault in

the optic nerve, or in those who had one of their eyes taken out, make it appear, that there is no such intimate union of substance; the optic nerve of the affected side only being wasted, while the other was large and plump. And the same observations are contradictory to the doctrine of a decussation of all the nerves, for the disease could be traced from the affected eye to the origin of the nerve on the same side.

These people whose optic nerves were not joined, having neither seen objects double, nor turned their eyes different ways, is also a plain proof, that the conjunction of the optic nerves will not serve to account for either the uniform motions of our eyes, or our seeing objects single with two eyes.

The retina of a recent eye, without any preparation, appears a very fine web, with some blood-vessels coming from its center to be distributed on it; but, after a good injection of the arteries that run in the substance of this nerve, as is common to other nerves, it is with difficulty that we can observe its nervous medullary substance. The situation of these vessels in the central part of the optic nerve, the want of medullary fibres here, and the firmness of this nerve before it is expanded at its entry into the ball of the eye, may be the reason why we do not see such bodies, or parts of bodies, whose picture falls on this central part of the retina.

The THIRD PAIR rise from the anterior part of the processus annularis, and piercing the dura mater a little before, and to a side of the ends of the posterior clinoid process of the sphenoid bone, run along the receptacula, or cavernous sinuses, at the side of the epiphysium, to get out at the foramina lacerata; after which each of them divides into branches, of which one, after forming a little ganglion, is distributed to the globe of the eye; the others are sent to the musculus rectus of the palpebra, and to the atollens, adductor, depressor, and obliquus minor muscles of the eye-ball. These muscles being principal instruments in the motions of the eye-lid and eye-ball, this nerve has therefore got the name of the MOTOR OCULI.

The FOURTH PAIR, which are the smallest nerves of any, derive their origin from the back-part of the base of the testes; and then making a long course on the side of the annular protuberance enter the dura mater a little farther back, and more externally than the third part, to run also along the receptacula, to pass out at the foramina lacerata, and to be entirely spent on the musculi trochleares, or superior oblique muscles of the eyes. These muscles being employed in performing the rotatory motions, and the advancement of the eye-balls forward, by which several of our passions are expressed, the nerves that serve them have got the name of PATHETICI.

The FIFTH PAIR are large nerves, rising from the annular processes where the medullary processes of the cerebellum join in the formation of that tuber, to enter the dura mater near the point of the petrous process of the temporal bones; and then sinking close by the receptacula at the sides of the sella tureca, each becomes in appearance thicker, and goes out of the skull in three great branches.

The first branch of the fifth is the OPHTHALMIC, which runs through the foramen lacerum, to the orbit, having

having in its passage thither a connection with the sixth pair. It is afterwards distributed to the ball of the eye with the third; to the nose, along with the olfactory, which the branch of the fifth that passes through the foramen orbitarium internum joins, as was already mentioned in the description of the first pair. This ophthalmic branch likewise supplies the parts at the internal canthus of the orbit, the glandula lacrimalis, fat, membranes, muscles, and teguments of the eye-lids; its longest farthest extended branch passing through the foramen supraciliare of the os frontis, to be distributed to the forehead.

The second branch of the fifth pair of nerves may be called MAXILLARIS SUPERIOR, from its serving principally the parts of the upper jaw. It goes out at the round hole of the sphenoid bone, and sends immediately one branch into the channel on the top of the antrum maxillare; the membrane of which and the upper teeth are supplied by it in its passage. As this branch is about to go out at the foramen orbitarium externum, it sends a nerve through the substance of the os maxillare to come out at Steno's duct, to be distributed to the fore-part of the palate; and what remains of it escaping at the external orbital hole, divides into a great many branches, that supply the cheek, upper lip, and nostril. The next considerable branch of the superior maxillary nerve, after giving branches which are reflected through the sixth hole of the sphenoid bone, to join the intercostal where it is passing through the skull with the carotid artery, and the portio dura of the seventh pair, as it passes through the os petrosum, is sent into the nose by the hole common to the palate and sphenoidal bone; and the remaining part of this nerve runs in the palato-maxillaris canal, giving off branches to the temples and pterygoid muscles, and comes at last into the palate to be lost.

The third or MAXILLARIS INFERIOR branch of the fifth pair going out at the oval hole of the sphenoid bone, serves the muscles of the lower jaw, and the muscles situated between the os hyoides and jaw: All the salivary glands, the amygdalæ, and the external ear, have branches from it: It has a large branch lost in the tongue, and sends another through the canal in the substance of the lower jaw to serve all the teeth there, and to come out at the hole in the fore-part of the jaw, to be lost in the chin and under lip.

The SIXTH PAIR, which is the smallest except the fourth, rises from the fore-part of the corpora pyramidalia; and each entering the dura mater some way behind the posterior clinoid process of the sphenoid bone, has a long course below that membrane, and within the receptaculum at the side of the sella turcica, where it is immersed in the blood of the receptacle: It goes afterwards out at the foramen lacerum into the orbit, to serve the abductor muscle of the eye.—A defect in this nerve may therefore be one cause of a strabismus.—In the passage of this nerve below the dura mater, it lies very contiguous to the internal carotid artery, and to the ophthalmic branch of the fifth pair of nerves. At the place where the sixth pair is contiguous to the carotid, a nerve either goes from each of them in an uncommon way, to wit, with the angle beyond where it rises obtuse, to descend with the artery, and to form the beginning of the

intercostal nerve, according to the common description; or, according to other authors, this nerve comes up from the great ganglion of the intercostal, to be joined to the sixth here.

The SEVENTH PAIR comes out from the lateral part of the annular process behind where the medullary process of the cerebellum are joined to that tuber; and each being accompanied with a larger artery than most other nerves, enters the internal meatus auditorius, where the two large bundles of fibres, of which it appeared to consist within the skull, soon separate from each other; one of them entering by several small holes into the vestibule, cochlea, and semicircular canals, is stretched on this inner camera of the ear in a very soft pulpy substance; and being never seen in the form of a firm cord, such as the other parcel of this and most other nerves become, is called PORTIO MOLLIS of the auditory nerve.

The other part of this seventh pair passes through Galen's foramen cœcum, or Fallopius's aquæduct, in its crooked passage by the side of the tympanum; in which passage, a nerve sent from the lingual branch of the inferior maxillary nerve, along the outside of the tuba Eustachiana, and crosses the cavity of the tympanum, where it has the name of chorda tympani, is commonly said to be joined to it. The very acute angle which this nerve makes with the fifth, or the sudden violent reflection it would suffer on the supposition of its coming from the fifth to the seventh, appears unusual; whereas, if we suppose that it comes from the seventh to the fifth, its course would be more in the ordinary way, and the chorda tympani would be esteemed a branch of the seventh pair going to join the fifth, the size of which is increased by this acquisition. This smaller bundle of the seventh gives branches to the muscles of the malleus, and to the dura mater, while it passes through the bony crooked canal; and at last comes out in a firm chord named PORTIO DURA, at the end of this canal, between the styloid and mastoid processes of the temporal bone, giving immediately filaments to the little oblique muscles of the head, and to those that rise from the styloid process. It then pierces through the parotid gland, and divides into a great many branches, which are dispersed in the muscles and teguments that cover all the side of the upper part of the neck, the whole face and cranium, as far back as the temples, including a considerable part of the external ear.

The EIGHTH PAIR of nerves rise from the lateral bases of the corpora olivaria in disgregated fibres; and as they are entering the anterior internal part of the holes common to the os occipitis and temporum, each is joined by a nerve which ascends within the dura mater from the tenth of the head, the first, second and inferior cervical nerves: This every body knows has the name of the NERVUS ACCESSORIUS. When the two get out of the skull, the accessorius separates from the eighth, and, descending obliquely outwards, passes through the sterno-mastoideus muscle, to which it gives branches, and afterwards terminates in the trapezius and rhomboid muscles of the scapula. In this course it is generally more or less joined by the second cervical nerve.

The large EIGHTH PAIR, soon after its exit, gives

nerves to the tongue, larynx, pharynx, and ganglion of the intercostal nerve, and being disjoined from the ninth and intercostal, to which it adheres closely some way, runs straight down the neck behind the internal jugular vein, and at the external side of the carotid artery. As it is about to enter the thorax, a large nerve goes off from the eighth of each side: This branch of the right-side turns round from the fore to the back part of the subclavian artery, while the branch of the left-side turns round the great curve of the aorta; and both of them mounting up again at the side of the œsophagus, to which they give branches, are lost at last in the larynx. These are called the RECURRENT nerves, which we are desired to shun in the operation of bronchotomy, though their deep situation protects them sufficiently.

The eighth pair, above, and at or near the place where the recurrent nerves go off from it, or frequently the recurrences themselves, send off small nerves to the pericardium, and to join with the branches of the intercostal that are distributed to the heart; but their size and situation are uncertain.

After these branches are sent off, the par vagum on each side descends behind the great branch of the trachea, and gives numerous filaments to the lungs, and some to the heart in going to the œsophagus. The one of the left-side running on the fore-part of the œsophagus, communicates by several branches with the right one in its descent to be distributed to the stomach: The right one gets behind the œsophagus, where it splits and rejoins several times before it arrives at the stomach, to which it sends nerves; and then being joined by one or more branches from the left trunk, they run towards the cœliac artery, there to join into the great semilunar ganglion formed by the two intercostals.

The NINTH PAIR of nerves comes from the inferior part of the corpora pyramidalia, to go out of the skull at their proper holes of the occipital bone. After their egress they adhere for some way firmly to the eighth and intercostal; and then sending a branch, that in many subjects is joined with branches of the first and second cervical nerves, to be distributed to the thyroid gland and muscles on the fore-part of the trachea arteria, the ninth is lost in the muscles and substance of the tongue.

The TENTH PAIR rises in separate threads from the sides of the spinal marrow, to go out between the os occipitis and first vertebra of the neck. After each of them has given branches to the great ganglion of the intercostal, 8th, 9th, and 1st cervical nerves, it is distributed to the straight, oblique, and some of the extensor muscles of the head.

The branch reflected from the sixth pair, joined possibly by some filaments of the ophthalmic branch of the fifth, runs along with the internal carotid artery, through the crooked canal formed for it in the temporal bone, where the little nerve is very soft and pappy, and in several subjects divides and unites again, and is joined by one or more branches from the fifth particularly of its superior maxillary branch, before it comes out of the skull. As soon as the nerve escapes out of this bony canal, it is connected a little way with the eighth and ninth; then separating from these, after seeming to receive addition-

al nerves from them, it forms a large ganglion, into which branches from the tenth of the head, and from the first and second cervical, enter. From this ganglion the nerves come out again small, to run down the neck along with the carotid artery, communicating by branches with the cervical nerves, and giving nerves to the muscles that bend the head and neck. As the intercostal is about to enter the thorax, it forms another ganglion, from which nerves are sent to the trachea and to the heart; these designed for the heart joining with the branches of the eighth, and most of them passing between the two great arteries and the auricles, to the substance of that muscle. The intercostal after this consisting of two branches, one going behind, and the other running over the fore-part of the subclavian artery, forms a new ganglion where the two branches unite below that artery, and then descending along the sides of the vertebrae of the thorax, receives branches from each of the dorsal nerves; which branches appearing to come out between the ribs, have given the name of intercostal to the whole nerve. Where the addition is made to it from the fifth dorsal nerve, a branch goes off obliquely forwards; which being joined by such branches from the sixth, seventh, eighth, and ninth dorsal, an anterior trunk is formed, and passes between the fibres of the appendix musculosa of the diaphragm, to form, along with the other intercostal and the branches of the eighth pair, a large semilunar ganglion situated between the cœliac and superior mesenteric arteries; the roots of which are as it were involved in a sort of nervous net-work of this ganglion, from which a great number of very small nervous threads run out to be extended on the surface of all the branches of those two arteries, so as to be easily seen when any of the arteries are stretched, but not to be raised from them by dissection; and thus the liver, gall-bladder, duodenum, pancreas, spleen, jejunum, ilium, and a large share of the colon, have their nerves sent from this great solar ganglion or plexus.

Several fibres of this ganglion, running down upon the aorta, meet with other nerves sent from the posterior trunk of the intercostal, which continues its course along the sides of the vertebra, they supply the glandulae renales, kidneys, and testes in men, or ovaria in women; and then they form a net-work upon the inferior mesenteric artery where the nerves of the two sides meet, and accompany the branches of this artery to the part of the colon that lies in the left side of the belly, and to the rectum, as far down as to the lower part of the pelvis.

The intercostal continuing down by the side of the vertebrae of the loins, is joined by nerves coming from between these vertebrae, and sends nerves to the organs of generation and others in the pelvis, being even joined with those that are sent to the inferior extremities.

The SPINAL NERVES rise generally by a number of disgregated fibres from both the fore and back part of the medulla spinalis, and soon after form a little knot or ganglion, where they acquire strong coats, and are extended into firm cords. They are distinguished by numbers, according to the vertebrae from between which they come out; the superior of the two bones forming the hole through which they pass, being the one from which the number

number is applied to each nerve. There are generally said to be thirty pair of them; seven of which come out between the vertebrae of the neck, twelve between those of the back, five between those of the loins, and six from the false vertebrae.

The FIRST CERVICAL pair of nerves comes out between the first and second vertebrae of the neck; and having given branches to join with the tenth pair of the head, the second cervical and intercostal, and to serve the muscles that bend the neck, it sends its largest branches backwards to the extensor muscles of the head and neck; some of which piercing through these muscles, run up on the occiput to be lost in the teguments here; and many fibres of it advance so far forward as to be connected with the fibrils of the first branch of the fifth pair of the head, and of the portio dura of the auditory nerve.

The SECOND CERVICAL is soon joined, by some branches, to the ninth of the head and intercostal, and to the first and third of the neck; then has a large branch that comes out at the exterior edge of the sterno-mastoideus muscle, where it joins with the accessorius of the eighth pair; and is afterwards distributed to the platysma myoides, teguments of the side of the neck and head, parotid gland, and external ear, being connected to the portio dura of the auditory nerve, and to the first cervical. The remainder of this second cervical is spent on the levator scapulae and the extensors of the neck and head. Generally a large branch is here sent off to join the accessorius of the eighth pair, near the superior angle of the scapula.

The THIRD PAIR of the neck passes out between the third and fourth cervical vertebrae; having immediately a communication with the second, and sending down a branch, which being joined by a branch from the fourth cervical, forms the PHRENIC nerve. This descending, enters the thorax, between the subclavian vein and artery; and then being received into a groove, formed for it in the pericardium, it has its course along this capsula of the heart, till it is lost in the middle part of the diaphragm. The right phrenic has a straight course; but the left one is obliged to make a considerable turn outwards, to go over the prominent part of the pericardium, where the point of the heart is lodged.—The middle of the diaphragm scarce could have been supplied by any other nerve which could have had such a straight course as the phrenic has.

The other branches of the third cervical nerve are distributed to the muscles and teguments at the lower part of the neck and top of the shoulder.

The FOURTH CERVICAL nerve, after sending off that branch which joins with the third to form the phrenic, and bestowing twigs on the muscles and glands of the neck, runs to the arm-pit, where it meets with the FIFTH, SIXTH, and SEVENTH cervicals, and FIRST DORSAL, that escape in the interstices of the musculi scaleni, to come at the arm-pit, where they join, separate, and rejoin, in a way scarce to be rightly expressed in words; and, after giving several considerable nerves to the muscles and teguments which cover the thorax, they divide into several branches, to be distributed to all the

parts of the superior extremity. Seven of these branches we shall describe under particular names.

1. SCAPULARIS runs straight to the cavitas femilunata of the upper costa of the scapula, which is a hole, in the recent subject, by a ligament being extended from one angle of the bone to the other, giving nerves in its way to the muscles of the scapula. When it has passed this hole, it supplies the supra-spinatus muscle; and then descending at the anterior root of the spine of the scapula, it is lost in the other muscles that lie on the dorsum of that bone.

2. ARTICULARIS sinks downward at the axilla, to get below the neck of the head of the os humeri, and to mount again at the back-part of it; so that it almost surrounds the articulation, and is distributed to the muscles that draw the arm back, and to those that raise it up.

3. CUTANEUS runs down the fore-part of the arm, near the skin, to which it gives off branches; and then divides, on the inside of the fore-arm, into several nerves, which supply the teguments there, and on the palm of the hand.

4. MUSCULO-CUTANEUS, or perforans Casseri, passes through the coraco-brachialis muscle; and, after supplying the biceps flexor cubiti and brachii internus, passes behind the tendon of the biceps, and over the cephalic vein, to be bestowed on the teguments on the outside of the fore-arm and back of the hand.

5. MUSCULARIS has a spiral course from the axilla, under the os humeri, and backward to the external part of that bone, supplying by the way the extensor muscles of the fore-arm, to which it runs between the two brachii muscles, and within the supinator radii longus.—At the upper part of the fore-arm, it sends off a branch, which accompanies the supinator longus till it comes near the wrist, where it passes obliquely over the radius, to be lost in the back of the hand and fingers. The principal part of this nerve pierces through the supinator radii brevis, to serve the muscles that extend the hand and fingers, whose actions are not injured when the supinator acts.

6. ULNARIS is extended along the inside of the arm, to give nerves to the muscles that extend the fore-arm, and to the teguments of the elbow: Towards the lower part of the arm, it flants a little backward, to come at the groove behind the internal condyle of the os humeri, through which it runs to the ulna: In its course along this bone, it serves the neighbouring muscles and teguments; and as it comes near the wrist, it detaches a branch obliquely over the ulna to the back of the hand, to be lost in the convex part of several fingers. The larger part of the nerve goes straight forward to the internal side of the os pisiforme of the wrist; where it sends off a branch which sinks under the large tendons in the palm, to go cross to the other side of the wrist, serving the musculi lumbricales and interossei, and at last terminating in the short muscles of the thumb and fore-finger. What remains of the ulnar nerve, after supplying the short muscles of the little finger, divides into three branches; whereof two are extended along the sides of the sheath of the tendons of the flexors of the little finger, to furnish the concave side of that finger; and the third

third branch is disposed in the same way upon the side of the ring-finger next to the little finger.

When we lean or press on the internal condyle of the os humeri, the numbness and prickling we frequently feel, point out the course of this nerve.

7. RADIALIS accompanies the humeral artery to the bending of the elbow, serving the flexors of the cubit in its way; then passing through the pronator radii teres muscle, it gives nerves to the muscles on the fore-part of the forearm, and continues its course near to the radius, bestowing branches on the circumjacent muscles. Near the wrist, it sometimes gives off a nerve, which is distributed to the back of the hand, and the convex part of the thumb, and several of the fingers, instead of the branch of the muscular. The larger part of this nerve, passing behind the annular ligament of the wrist, gives nerves to the short muscles of the thumb; and afterwards sends a branch along each side of the sheath of the tendons of the flexors of the thumb, fore-finger, mid-finger, and one branch to the side of the ring-finger, next to the middle one, to be lost on the concave side of those fingers.

Though the radial nerve passes through the pronator muscle, and the muscular nerve seems to be still more unfavourably placed within the supinator brevis; yet the action of these muscles do not seem to have any effect in hindering the influence of these nerves, for the fingers or hand can be bended while pronation is performing vigorously, and they can be extended while supination is exercised.

The manner of the going off of these nerves of the fingers, both from the ulnar and radial, is, that a single branch is sent from the trunk to the side of the thumb and little finger, farthest from the other fingers; and all the rest are supplied by a trunk of a nerve, which splits into two some way before it comes as far as the end of the metacarpus, to run along the sides of different fingers that are nearest to each other.

It might have been observed, that, in describing the posterior branches of the ulnar and muscular nerve, we did not mention the particular fingers, to the convex part of which they are distributed. The reason of this omission is, the uncertainty of their distribution; for though sometimes these posterior branches go to the same fingers, to the concave part of which the anterior branches of the ulnar and radial are sent, yet frequently they are distributed otherwise.

The situation of these brachial nerves in the axilla, may let us see how a weakness and atrophy may be brought on the arms by a long continued pressure of crutches, or such other hard substances on this part; and the course of them from the neck to the arm, may teach us, how much better effects vesicatories, or stimulating nervous medicines, would have, when applied to the skin, covering the transverse processes of the vertebrae of the neck, or at the axilla, than when they are put between the shoulders, or upon the spinal processes, in convulsions or palsies of the superior extremities, where a stimulus is required.

The TWELVE DORSAL nerves of each side, as soon as they escape from between the vertebrae, send a branch

forward to join the intercostal, by which a communication is made among them all; and they soon likewise give branches backwards to the muscles that raise the trunk of the body, their principal trunk being extended outwards, to come at the furrow in the lower edge of each rib, in which they run toward the anterior part of the thorax, between the internal and external intercostal muscles, giving off branches in their course to the muscles and teguments of the thorax.

The FIRST DORSAL, as was already observed, is particular in this, that it contributes to form the brachial nerves; and that the two branches of the intercostal, which come down to the thorax, form a considerable ganglion with it.

The SIX lower dorsal nerves give branches to the diaphragm and abdominal muscles.

The TWELFTH joins with the first lumbar, and bestows nerves on the musculus quadratus lumborum and iliacus internus.

As the intercostal is larger in the thorax than any where else, and seems to diminish gradually as it ascends and descends, there is cause to suspect that this is the trunk from which the superior and inferior pairs are sent as branches.

The FIVE LUMBAR nerves on each side communicate with the intercostal and with each other, and give branches backwards to the loins.

The FIRST communicates with the last dorsal, sends branches to the abdominal muscles, to the psoas and iliacus, and to the teguments and muscles on the fore-part of the thigh; while its principal branch joins with the other nerves, to form the crural nerve.

The SECOND LUMBAR nerve passes through the psoas muscle, and is distributed nearly in the same way as the former: as is also the THIRD.

Branches of the second, third, and fourth, make up one trunk, which runs along the fore-part of the pelvis; and, passing in the notch at the fore-part of the great hole common to the os pubis and ischium, is spent on the adductor muscles, and on the teguments on the inside of the thigh. This nerve is called the OUTURATOR, or POSTERIOR CRURAL NERVE.

By united branches from the first, second, third, and fourth lumbar nerves, a nerve is formed that runs along the psoas muscle, to escape with the external iliac vessels out of the abdomen, below the tendinous arcade of the external oblique muscle. This nerve, which is named the ANTERIOR CRURAL, is distributed principally to the muscles and teguments on the fore-part of the thigh. A branch, however, of this nerve runs down the inside of the leg to the upper part of the foot, keeping near to the vena saphena; in opening of which with a lancet at the ankle, the nerve is sometimes hurt, and occasions sharp pain at the time of the operation, and numbness afterwards.

The SIXTH PAIR of the false VERTEBRÆ consist each of small posterior branches, sent to the hips, and of large anterior branches.

The first, second, and third, after coming through the three upper holes in the fore-part of the os sacrum, join together with the fourth and fifth of the loins, to form

form the largest nerve of the body, which is well known by the name of SCIATIC or ISCHIATIC nerve: This, after sending large nerves to the different parts of the pelvis, and to the external parts of generation, and the podex, as also to the muscles of the hips, passes behind the great tuber of the os ischium, and then over the quadrigemini muscles, to run down near to the bone of the thigh at its back-part, giving off nerves to the neighbouring muscles and teguments. Some way above the ham, where it has the name of the popliteus nerve, it sends off a large branch that passes over the fibula, and sinking in among the muscles on the anterior external part of the leg, runs down to the foot, to be lost in the upper part of the larger toes, supplying the neighbouring muscles and teguments every where in its passage. The larger branch of the sciatic, after giving branches to the muscles and teguments about the ham and knee, and sending a large cutaneous nerve down the calf of the leg, to be lost at last on the outside of the foot and upper part of the lesser toes, sinks below the gemellus muscle, and distributes nerves to the muscles on the back of the leg; among which it continues its course, till passing behind the internal malleolus, and in the internal hollow of the os calcis, it divides into the two plantar nerves: The internal of which is distributed to the toes, in the same manner that the radial nerve of the hand serves the concave side of the thumb and fingers; and the external plantar is divided and distributed to the sole of the foot and toes, nearly as the ulnar nerve is in the palm of the hand, and in the concave part of the fingers.

Several branches of these nerves, that serve the inferior extremities, pierce through muscles.

The FOURTH, which, with the two following, is much smaller than the three superior, soon is lost in the vesica urinaria and intestinum rectum.

The FIFTH comes forward between the extremity of

the os sacrum and coccygis, to be distributed principally to the levatores ani.

The SIXTH, which some think to be only a production of the dura mater, advances forward below the broad shoulders of the first bone of the os coccygis, and is lost in the sphincter ani and teguments covering it.

The size of the nerves of the inferior extremities seems larger proportionally than in the superior extremities; the inferior extremities having the weight of the whole body to sustain, and that frequently at a great disadvantage.—What the effect is of the nerves here being injured, we see daily, when people happen, by sitting wrong, to compress the sciatic nerve, they are incapable for some time after to support themselves on the affected extremity; and this is still more remarkable in the sciatic or hip-gout, in which the member is not only weakened, but gradually shrivels and wastes.

USES of the Nerves.

MANY experiments concur in proving, that the nerves are the instruments of sensation. As to the mode of their operation, several different theories have been given. Some suppose, that they are elastic cords, resembling fiddle-strings; and that they convey sensations to the brain by a kind of vibratory motion. Others have supposed them to be tubular, and to contain a fluid called animal spirits; and that sensation is produced by the motions and counter-motions of this fluid. Many useless volumes have been wrote upon each of these hypotheses.—Another and more recent theory supposes, that the nerves are not tubular, but that they are pervaded by a subtle elastic fluid called Ether; and that sensation, &c. are occasioned by the oscillations of that fluid. A few detached and ill-digested scraps of this theory have already appeared in some temporary productions, the principal of which has been sufficiently animadverted upon under the word ETHER.

EXPLANATION OF PLATE XVIII.

FIG. 1. Represents the inferior part of the brain;—the anterior part of the whole spine, including the medulla spinalis;—with the origin and large portions of all the NERVES.

A A, The anterior lobes of the cerebrum. B B, The lateral lobes of the cerebrum. C C, The two lobes of the cerebellum. D, Tuber annulare. E, The passage from the third ventricle to the infundibulum. F, The medulla oblongata, which sends off the medulla spinalis through the spine. G G, That part of the os occipitis which is placed above (H H), the transverse processes of the first cervical vertebra. I I, &c. The seven cervical vertebrae, with their intermediate cartilages. K K, &c. The twelve dorsal vertebrae, with their intermediate cartilages. L L, &c. The five lumbar vertebrae, with their intermediate cartilages. M, The os sacrum. N, The os coccygis.

NERVES.—1 1, The first pair of nerves, named olfactory, which go to the nose. 2 2, The second pair, named optic, which goes to form the tunica retina of the eye. 3 3, The third pair, named motor oculi; it supplies most of the muscles of the eye-ball.

VOL. I. NO. 11.

3

4 4, The fourth pair, named pathetic,—which is wholly spent upon the musculus trochlearis of the eye.

5 5, The fifth pair divides into three branches.—The first, named ophthalmic, goes to the orbit, supplies the lachrymal gland, sends branches out to the forehead and nose.—The second, named superior maxillary, supplies the teeth of the upper jaw, and some of the muscles of the lips.—The third, named inferior maxillary, is spent upon the muscles and teeth of the lower jaw, tongue, and muscles of the lips.

6 6, The sixth pair, which, after sending off the beginning of the intercostal or great sympathetic, is spent upon the abductor oculi.

7 7, The seventh pair, named auditory, divides into two branches.—The largest, named portio mollis, is spent upon the internal ear.—The smallest, portio dura, joins to the fifth pair within the internal ear by a reflected branch from the second of the fifth, and within the tympanum, by a branch from the third of the fifth, named chorda tympani.—Vid. fig. 3. near B. 8 8, &c. The eighth pair, named par vagum,—which accompanies the intercostal, and is spent upon the tongue, larynx, pharynx,

3 S

rynx,

rinx, lungs, and abdominal viscera. 9 9, The ninth pair, which are spent upon the tongue. 10 10, &c. The intercostal, or great sympathetic, which is seen from the sixth pair to the bottom of the pelvis on each side of the spine, and joining with all the nerves of the spine;—in its progress supplying the heart, and, with the par vagum, the contents of the abdomen and pelvis. 11 11, The accessorius, which is spent upon the sterno-cleido-mastoideus and trapezius muscles. 12 12, The first cervical nerves;—13 13, The second cervical nerves;—both spent upon the muscles that lie on the neck, and teguments of the neck and head. 14 14, The third cervical nerves, which, after sending off (15 15, &c.) the phrenic nerves to the diaphragm,—supply the muscles and teguments that lie on the side of the neck and top of the shoulder. 16 16, The brachial plexus, formed by the fourth, fifth, sixth, seventh cervicals, and first dorsal nerves,—which supply the muscles and teguments of the superior extremity. 17 17, The twelve dorsal, or proper intercostal nerves, which are spent upon the intercostal muscles and some of the large muscles which lie upon the thorax. 18 18, The five lumbar pairs of nerves, which supply the lumbar and abdominal muscles, and some of the teguments and muscles of the inferior extremity. 19 19, The sacro-sciatic, or posterior crural nerve, formed by the two inferior lumbar, and three superior of the os sa-

crum.—This large nerve supplies the greatest part of the muscles and teguments of the inferior extremity. 20, The stomachic plexus, formed by the eighth pair. 21 21, Branches of the solar or cœliac plexus, formed by the eighth pair and intercostals, which supply the stomach and chylopoetic viscera. 22 22, Branches of the superior and inferior mesenteric plexuses, formed by the eighth pair and intercostals, which supply the chylopoetic viscera, with part of the organs of urine and generation. 23 23, Nerves which accompany the spermatic cord. 24 24, The hypogastric plexus, which supplies the organs of urine and generation within the pelvis.

FIG. 2, 3, 4, 5. Shews different views of the inferior part of the brain, cut perpendicularly through the middle,—with the origin and large portions of all the nerves which pass out through the bones of the cranium,—and the three first cervicals.

A, The anterior lobe. B, The lateral lobe of the cerebrum. C, One of the lobes of the cerebellum. D, Tuber annulare. E, Corpus pyramidale, in the middle of the medulla oblongata. F, The corpus ovare, in the side of the medulla oblongata. G, The medulla oblongata. H, The medulla spinalis.

NERVES.—1 2 3 4 5 6 7 8 & 9, Pairs of nerves. 10 10, Nervus accessorius, which comes from—11 12 & 13, the three first cervical nerves.

P A R T VI.

Of such Parts of the Body as could not properly be described under any of the former general Divisions.

SECT. I. Of the common Integuments.

THE SKIN.

THE skin is a substance of very large extent, made up of several kinds of tendinous, membranous, vascular, and nervous fibres, the intertexture of which is so much the more wonderful, as it is difficult to unfold; for their directions are as various as those of the stuff of which an hat consists.

This texture is what we commonly call leather, and it makes, as it were, the body of the skin. It is not easily torn, may be elongated in all directions, and afterwards recovers itself, as we see in fat persons, in women with child, and in swellings; and it is thicker and more compact in some places than in others.

Its thickness and compactness are not, however, always proportionable; for on the posterior parts of the body, it is thicker and more lax than on the fore-parts; and on the palms of the hands, and soles of the feet, it is both very thick and very solid.

The outer surface of this substance is furnished with small eminences, which anatomists have thought fit to

call papillæ, in which the capillary filaments of the cutaneous nerves terminate by small radiated pencils.

These papillæ differ very much in figure and disposition in the different parts of the body, and they may be distinguished into several kinds.

The greatest part of them is flat, of different breadths, and separated by fulci, which form a kind of irregular lozenges. The pyramidal figure ascribed to them, is not natural, and appears only when they are contracted by cold or by diseases.

The papillæ of the palm of the hand, of the sole of the foot, and of the fingers and toes, are higher than on the other parts of the body; but they are likewise smaller, closely united together, and placed as it were endwise, with respect to each other, in particular rows, which represent on the skin all kinds of lines, straight, crooked, waving, spiral, &c. These several lines are often distinctly visible in those parts of the palm of the hand which are next the first phalanges of the fingers.

The red part of the lips is made up of papillæ, representing very fine hairs or villi, closely united together.

There is another particular kind under the nails; the papillæ being there more pointed, or in a manner conical, and turned obliquely towards the ends of the fingers. Those

Those which are found in the hairy scalp, scrotum, &c. are still of other kinds.

The papillæ of the first and second kinds appear to be surrounded at their bases by a soft mucilaginous and pretty viscous substance, which fills the interstices between them, and represents a kind of net-work or sieve, the meshes or holes of which surround each papilla. This substance is commonly called corpus reticulare, or mucosum.

This vascular texture is of various forms and figures in the different parts of the body.

The inner surface of the skin is covered by very small tubercles, commonly called cutaneous glands, or glandulæ miliares.

These tubercles are partly fixed in small fossulæ, in the substance of the skin, which answer to the same number of small cavities in the corpus adiposum. Their excretory ducts open on the outer surface of the skin, sometimes in the papillæ, and sometimes on one side of them.

The greatest part of them furnishes sweat, and others a fatty oily matter of different thicknesses, as in the hairy scalp, in the back, behind the ears, and at the lower part of the nose, where this matter may be squeezed out, in form of small worms.

Besides these corpuscles, there are other small solid bodies, almost of an oval figure, contained in the substance of the skin. These are the roots or bulbs from whence the hairs arise, and some of them are situated within the inner surface of the skin.

The skin has several considerable openings, some of which have particular names; such as the fissure of the palpebræ, the nares, the mouth, the external foramen of the ears, the anus, and openings of the parts of generation.

Besides these, it is perforated by an infinite number of small holes, called pores, which are of two kinds. Some are more or less perceivable to the naked eye; such as the orifices of the milky ducts of the mammae, the orifices of the excretory canals of the cutaneous glands, and the passages of the hairs.

The other pores are imperceptible to the naked eye, but visible through a microscope; and their existence is likewise proved by the cutaneous transpiration, and by the effects of topical applications; and from these two phenomena, they have been divided into arterial and venal pores.

THE CUTICULA, OR EPIDERMIS.

The outside of the skin is covered by a thin transparent web, closely joined to it, which is called epidermis, cuticula, or the scarf-skin.

The substance of the cuticula appears to be very uniform on the side next the skin, and to be composed on the other side of a great number of very fine small squamous laminae, without any appearance of a fibrous or vascular texture, except some small filaments, by which it is connected to the papillæ.

This substance is very solid and compact, but yet capable of being extended and thickened, as we see by

steeping it in water, and by the blisters raised on the skin by vesicatories. It yields very much in swellings; but not so much as the skin, without breaking or cracking.

Hard and reiterated frictions loosen it insensibly, and presently afterward, a new stratum arises, which thrusts the first outward, and may itself be loosened and thrust outward by a third stratum, and so on.

The epidermis adheres very closely to the cutaneous papillæ, from which it may be separated by boiling; or by steeping, for a long time, in cold water.

It adheres still closer to the corpus reticulare, which is easily raised along with it; and they seem to be true portions or continuations of each other.

The epidermis covers the skin through its whole extent, except at the places where the nails lie. It is marked with the same furrows and lozenges as the skin, and has the same openings and pores; and though it may be said to pass the bounds of the skin, where it is continued inward, through the great openings, yet at these places it loses the name of epidermis.

When we examine narrowly the small pores or holes, through which the sweat passes, the epidermis seems to enter these, in order to complete the excretory tubes of the cutaneous glands. The fossulæ of the hairs have likewise the same productions of the epidermis, and it seems to give a sort of coat or bark to the hairs themselves. Lastly, the almost imperceptible ducts of the cutaneous pores are lined by it.

USES OF THE SKIN.

It is chiefly and properly the filamentary substance, called the body of the skin, which is the universal integument of the body, and the basis of all the other cutaneous parts; each of which has its particular uses.

The skin is able to resist external injuries to a certain degree, and such impressions, frictions, strokes, &c. to which the human body is often liable, as would hurt, wound, and disorder the parts of which it is composed, if they were not defended by the skin.

The papillæ are the organ of feeling, and contribute to an universal evacuation, called insensible transpiration. They likewise serve to transmit from without, inwards, the subtle particles or impressions of some things applied to the skin. The first of these three uses depends on the extremities of the nerves, the second on the arterial productions, and the third on the productions of the veins.

The cutaneous glands secrete an oily humour of different consistences, and they are likewise the origin of sweat.

The epidermis serves to keep the pencils or nervous filaments of the papillæ in an even situation, and without confusion; and it likewise moderates the impressions of external objects.

Another use of the epidermis is to regulate the cutaneous evacuations already mentioned, the most considerable of which is insensible transpiration.

THE MEMBRANA ADIPOSA, AND FAT.

The second universal integument of the human body,

is the membrana adiposa, or corpus adiposum. This is not, however, a single membrane, but a congeries of a great number of membranous laminae, joined irregularly to each other at different distances, so as to form numerous interstices of different capacities, which communicate with each other. These interstices have been named cellulae, and the substance made up of them, the cellulose substance.

The thickness of the membrana adiposa is not the same all over the body, and depends on the number of laminae of which it is made up. It adheres very closely to the skin, runs in between the muscles in general, and between their several fibres in particular, and communicates with the membrane which lines the inside of the thorax and abdomen.

The structure is demonstrated every day by butchers, in blowing up their meat, when newly killed; in doing which, they not only swell the membrana adiposa, but the air insinuates itself likewise in the interstices of the muscles, and penetrates even to the viscera, producing a kind of artificial emphysema.

These cellular interstices are so many little bags or satchels, filled with an unctuous or oily juice, more or less liquid, which is called fat.

This substance increases in quantity in the body, by rest and good living; and on the contrary, diminishes by hard labour and a spare diet.

The proportional differences in the thickness of this membrana adiposa, are determined, and may be observed to be regular in some parts of the body, where either beauty or use required it.

Thus we find it in great quantities, where the interstices of the muscles would otherwise have left disagreeable hollow or void places; but being filled, and as it were padded with fat, the skin is raised, and an agreeable form given to the part.

In some parts of the body the fat serves for a cushion, pillow, or mattress; as on the buttocks, where the laminae and cells are very numerous.

The fat is likewise of great use to the muscles, in preserving the flexibility necessary for their actions, and in preventing or lessening their mutual frictions.

THE NAILS.

The substance of the nails is like that of horn, and they are composed of several planes of longitudinal fibres soldered together. These strata end at the extremity of each finger, and are all nearly of an equal thickness, but of different lengths.

The external plane or stratum is the longest, and the rest decrease gradually, the innermost being the shortest; so that the nail increases in thickness from its union with the epidermis, where it is thinnest, to the end of the finger, where it is thickest.

The graduated extremities or roots of all the fibres of which these planes consist, are hollowed for the reception of the same number of very small oblique papillae, which are continuations of the true skin, which having reached to the root of the nail, forms a semilunar fold, in which that root is lodged.

After this semilunar fold, the skin is continued on the whole inner surface of the nail. The fold of the skin is accompanied by the epidermis, to the root of the nail exteriorly, to which it adheres very closely.

Three parts are generally distinguished in the nail, the root, body, and extremity. The root is white and in form of a crescent; and the greatest part of it is hid under the semilunar fold already mentioned.

The crescent and the fold lie in contrary directions to each other. The body of the nail is naturally arched, transparent, and appears of the colour of the cutaneous papillae which lie under it.

The principal use of the nails is to strengthen the ends of the fingers and toes, and to hinder them from being inverted towards the convex side of the hand or foot, when we handle or press upon any thing hard.

THE HAIRS.

The hairs belong as much to the integuments as the nails. They are a kind of reeds or rushes, the roots or bulbs of which lie toward that side of the skin which is next the membrana adiposa. The trunk or beginning of the stem perforates the skin, and the rest of the stem advances beyond the outer surface of the skin, to a certain distance, which is very various in the different parts of the body.

When the different hairs are examined by a microscope, we find the roots more or less oval, the largest extremity being either turned toward, or fixed in the corpus adiposum.

This oval root is covered by a whitish strong membrane, in some measure elastic; and it is connected either to the skin, to the corpus adiposum, or to both, by a great number of very fine vessels and nervous filaments.

Within the root, we observe a kind of glue, some very fine filaments of which advance toward the small extremity, where they unite and form the stem, which passes through this small extremity to the skin. As the stem passes through the root, the outer membrane is elongated in form of a tube, which closely invests the stem, and is entirely united to it.

The stem having reached the surface of the skin, pierces the bottom of a small fossula between the papillae, or sometimes a particular papilla, and there it meets the epidermis, which seems to be inverted round it, and to unite with it entirely. A sort of unctuous matter transudes through the sides of the fossula, which is bestowed on the stem, and accompanies it, more or less, as it runs out from the skin, in form of an hair.

SECT. II. Of the ABDOMEN.

The Abdomen begins immediately under the thorax, and terminates at the bottom of the pelvis of the ossa innominata. Its circumference, or outer surface, is divided into regions, of which there are three anterior, viz. the epigastric or superior region, the umbilical or middle region, and the hypogastric or lower region. There is but one posterior region, named regio lumbaris. The

The epigastric region begins immediately under the appendix ensiformis, at a small superficial depression, called the pit of the stomach, and ends above the navel at a transverse line, supposed to be drawn between the last false ribs on each side.

This region is subdivided into three parts; one middle, named epigastrium; and two lateral, termed hypochondria. The epigastrium takes in all that space which lies between the false ribs of both sides, and the hypochondria are the places covered by the false ribs.

The umbilical region begins above the navel, at the transverse line already mentioned, and ends below the navel at another transverse line, supposed to be drawn parallel to the former, between the two crizæ of the os ilium.

This region is likewise divided into three parts; one middle, which is properly the regio umbilicalis; and two lateral, called ilia, or the flanks; and they comprehend the space between the false ribs and upper part of the os ilium on each side.

The hypogastric region is extended downward from the inferior limit of the umbilical region, and is divided into three parts; one middle, called pubis; and two lateral, called inguina, or the groins.

The lumbar region is the posterior part of the abdomen, and comprehends all that space which reaches from the lowest ribs on each side, and the last vertebra of the back, to the os sacrum and neighbouring parts of the os ilium. The lateral parts of this region are termed the loins, but the middle part has no proper name in men.

Lastly, the bottom of the abdomen, which answers to the pelvis of the skeleton, is terminated anteriorly by the pudenda or parts of generation, and posteriorly by the clunes and anus. The buttocks are separated by a fossa, which leads to the anus; and each buttock is terminated downward by a large fold, which distinguishes it from the rest of the thigh.

The space between the anus and the parts of generation, is called perineum, and is divided into two equal lateral parts by a very distinct line, which is longer in males than in females.

The cavity of the abdomen, formed by the parts already mentioned, (all which are covered by the skin and membrana adiposa) is lined on the inside by a particular membrane, called peritoneum. It is separated from the cavity of the thorax by the diaphragm, and terminated below by the musculi levatores ani.

This cavity contains the stomach, and the intestines. It contains likewise the mesentery, mesocolon, omentum, liver, gall bladder, spleen, pancreas, glands of the mesentery, vasa lactea, receptaculum chyli, kidneys, renal glands, ureters, bladder, and the internal parts of generation in both sexes.

The whole fore-part of the abdomen forms an oblong convexity, like an oval vault, more or less prominent in the natural state, in proportion to the quantity of fat upon it, and of food contained in it, or to the different degrees of pregnancy in women. The hypogastric and umbilical regions are more subject to these varieties, than the epigastric region.

The appendix ensiformis of the sternum, the cartilaginous portions of the last pair of true ribs, those of the first four pairs of false ribs, all the fifth pair, the five lumbar vertebrae, the ossa innominata, the os sacrum, and os coccygis, form the bony sides of the cavity of the abdomen.

The diaphragm, the muscles called particularly musculi abdominis, the quadrati lumborum, psoas, iliaci, the muscles of the coccyx, and of the intestinum rectum, form the chief part of the circumference of this cavity.

The cavity of the abdomen is of an irregularly oval figure, but still symmetrical. On the foreside it is uniformly arched or oval, and its greatest capacity is even with the navel, and nearest part of the hypogastrium. On the upper side it is bounded by a portion of a vault, very much inclined. On the backside, it is in a manner divided into two cavities by the jutting out of the vertebrae of the loins. On the lower side, it contracts gradually all the way to the little edge of the pelvis, and from thence expands again a little as far as the os coccygis and tubercles of the ischium, terminating in the void space between these three parts.

PERITONÆUM.

HAVING carefully removed the muscles of the abdomen, the first thing we discover is the peritoneum, a membranous covering, which adheres immediately to the inner surface of the musculi transversi, and of all the other parts of this cavity; and involves and invests all the viscera contained therein, as in a kind of bag.

The peritoneum in general is a membrane of a pretty close texture, and yet very limber, and capable of a very great extension; after which it can recover itself, and be contracted to its ordinary size; as we see in pregnancy, dropsies, corpulency, and repletion.

It seems to be made up at least of two portions, one internal, the other external; which have been looked upon by many anatomists as a duplicature of two distinct membranous laminae. But, properly speaking, the internal portion alone deserves the name of a membranous lamina, as being the main body of the peritoneum. The external portion is no more than a kind of fibrous or follicular apophysis of the internal; and may properly enough be termed the cellular substance of the peritoneum.

The true membranous lamina, commonly called the internal lamina, is very smooth, and polished on that side which is turned to the cavity and viscera of the abdomen, and continually moistened by a serous fluid discharged through almost imperceptible pores.

The cellular substance, or external portion of the peritoneum, adheres very closely to the parts which form the insides of the cavity of the abdomen.

The cellular substance has several elongations, which have been called productions of the peritoneum. Two of these productions accompany and invest the spermatic ropes in males, and the vascular ropes, commonly called the round ligaments, in women. There are other two, which pass under the ligamentum Fallopii, with the

crural vessels, which they involve, and are gradually lost in their course downward.

To these four productions of the cellular substance of the peritoneum, we may add a fifth, which is spread on the neck of the bladder, and perhaps a sixth, which accompanies the intellinum rectum. All these elongations pass out of the cavity of the abdomen, and may be termed external, to distinguish them from others that remain in the abdomen, and are called internal, of which hereafter.

The great blood-vessels, that is, the aorta and vena cava, are likewise involved in this cellular substance of the peritoneum. In a word, it involves immediately and separately all the parts and organs which are commonly said to lie in the duplicature of the peritoneum.

It has, nevertheless, productions of its own, but they are very different from those of the cellular substance; for they run from without, inward; that is, they advance from the convex side of the great bag of the peritoneum, into the cavity of that bag, some more, some less, and also in different manners; as if the sides of a large ball or bladder were thrust inward into the cavity of the ball or bladder.

Of these internal elongations or intropressions of the true lamina of the peritoneum, some are simply folded, like a duplicature; some are expanded like inverted bags or saeculi to contain some viscera; some begin by a simple duplicature, and are afterwards expanded into a cavity, which contains some organ; some are alternately extended in the form of simple duplicatures, and of cavities; and lastly, some form only a small eminence on the inner surface of the great cavity of the peritoneum.

The chief uses of the peritoneum are, to line the cavity of the abdomen, to invest the viscera contained in that cavity as in a common bag, to supply them with particular coats, to form productions, ligaments, connexions, folds, vagine, &c.

The fine fluid which transfudes through the whole internal surface of the peritoneum, prevents the inconveniences which might arise from the continual frictions and motions to which the viscera of the abdomen are exposed either naturally or by external impulses.

VENTRICULUS, OR STOMACH.

The stomach is a great bag or reservoir, situated partly in the left hypochondrium, and partly in the epigastrium.

The figure of the stomach is like that of a bag-pipe, oblong, incurvated, large and capacious at one end, and small and contracted at the other.

The curvature of the stomach gives us occasion to distinguish two arches in it; one large, which runs along the greatest convexity; and one small, directly opposite to the former. The sides of the stomach, are the two lateral portions which lie between the two arches.

The stomach has two extremities, one large, and one small like a crooked funnel. It has two openings, called the orifices of the stomach, one between the great extremity and the small curvature, the other at the end of the small or contracted extremity. The first opening

is a continuation of the oesophagus; the other joins the intestinal canal, and is called pylorus.

The great extremity of the stomach is in the left hypochondrium, and for the most part immediately under the diaphragm.

The small extremity of the stomach does not reach to the right hypochondrium. It bends obliquely backward toward the upper orifice, so that the pylorus lies about two fingers breadth from the body of the vertebrae immediately under the small portion of the liver, and consequently lower down, and more forward than the other orifice by almost the same distance.

According to this natural situation, the stomach, especially when full, lies so as that the great curvature is turned more upward than downward, and the small curvature more backward than upward.

One of the lateral convex sides is turned upward, the other downward; and not forward and backward, as they appear in dead bodies, where the intestines do not support them in their natural situation.

The stomach is composed of several parts, the chief of which are the different strata which form its substance, to which anatomists give the name of tunicae or coats. These coats are commonly reckoned to be four in number, the outer or common, the fleshy or muscular, the nervous or aponeurotic, and the villous or inner coat; and they are afterwards subdivided several ways.

The first or outermost coat is simply membranous, being one of the internal productions of the peritoneum.

The second or muscular coat is made up of several planes of fibres, which may all be reduced to two, one external, the other internal. The external coat is longitudinal, though in different respects, following nearly the direction of the curvatures and convexities of the stomach; and the internal plane is transversely circular.

Between the outer and inner planes, round the superior orifice, there are two distinct planes, about the breadth of a finger, and very oblique, which surround this orifice in opposite directions, and intersect each other where they meet on the two lateral sides.

Along the middle of each lateral side of the small extremity, there runs a tendinous or ligamentary flat portion, above a quarter of an inch in breadth, which terminates in the pylorus. These two portions lie between the common and muscular coats, and adhere very strongly to the first.

Between the same two coats, there is a cellular substance which adheres very closely to the external coat, and insinuates itself between the fleshy fibres of the second, all the way to the third.

The third coat, called commonly tunica nervosa, sustains, on its convex side, a very large reticular distribution of capillary vessels and nerves. On the concave side, it seems to be of a very loose texture, and as it were spongy or filamentary, containing a great number of small glandular bodies, especially near the small curvature and small extremity of the stomach.

The fourth coat of the stomach is termed villosa, because, when it swims in clear water, some have imagined they saw something in it like the pile of velvet.

These two coats are of a larger extent than the two former,

former, and they join in forming large rugæ on the concave surface of the stomach, the greatest part of which are transverse, though irregular and waving.

In the interstices of these rugæ, there is often found a sort of slimy mucus, with which the whole cavity of the stomach seems likewise to be moistened. This mucus is much more fluid in living bodies, and is supplied by the glands of the stomach. It is termed sucus gastricus or stomachicus.

On the inner surface of the small extremity of the stomach, at the place where it ends in the intestinal canal, we observe a broad, thin, circular border, with a roundish hole in the middle. This hole is the inferior orifice of the stomach, called by the Greeks pylorus, which signifies a porter.

This border is a fold or duplicature of the two inner coats of the stomach, the nervosa and villosa; and it is formed in part by a fasciculus of fleshy fibres fixed in the duplicature of the tunica nervosa, and distinguished not only from the other fleshy fibres of the extremity of the stomach, but also from those of the intestines, by a thin, whitish circle, which appears even through the external or common coat, round the union of the stomach and intestines.

The figure of the pylorus is that of a ring, transversely flattened, the inner edge of which, or that next the center, is turned obliquely toward the intestines, like a broad portion of a funnel. This inner edge runs naturally more or less into little plaits or gathers, like the mouth of a purse almost shut. It is therefore a kind of sphincter, which can contract the inferior orifice of the stomach, but seems not capable of shutting it quite close.

The stomach receives in general whatever the mouth sends thither, through the canal of the œsophagus; but its particular use is to receive the aliments, to contain them for a longer or shorter time, in proportion as they are more solid or fluid, and to digest them, that is, to put them in a condition to be turned into that nutritious fluid called chyle.

This operation, which goes by the general name of digestion, and by which chylification begins, is performed partly by the sucus gastricus, which flows continually from the tunica villosa, and partly by the continual contraction and relaxation of the muscular coat.

The pylorus, or fleshy circle of the inferior orifice of the stomach, serves to retain the aliments in it, till they have acquired a sufficient degree of fluidity to pass easily through that opening.

The gentle and alternate motions of the orbicular fibres of the muscular coat, may assist in sending through the pylorus, in the natural way, the aliment that is sufficiently digested. This was called the peristaltic or vermicular motion, by those who believed that it is successively reiterated, like that of earth-worms when they creep.

The situation of the stomach, which is nearly transverse, is likewise of use in making the aliment remain long enough in that cavity, and may serve to make the length of this stay in some measure arbitrary, by means of the different postures of the body; for when we lie on the left side, the aliment must remain longer, than when we lie on the right, &c.

The INTESTINES in general, and Intestinum Duodenum in particular.

BETWEEN the pylorus and the very lowest part of the abdomen, lies a long canal, bent in a great many different directions, by numerous convolutions or turnings, called the intestines.

This canal, thus folded and turned, forms a considerable bulk, which fills the greatest part of the cavity of the abdomen; and it is connected, through its whole extent, to membranous productions or continuations of the peritoneum, principally to those called the mesentery and mesocolon.

The incurvations of the intestinal canal form two arches, a small one by which it is connected to the mesentery and mesocolon, and a great one on the opposite side, which lies loose. The whole canal is generally about seven or eight times as long as the body.

The intestines in general are composed of several coats, much in the same manner with the stomach. The first and outermost is a continuation of the mesentery, or of some other elongation or duplicature of the peritoneum.

This is commonly termed the common coat; and it has a cellular substance on its inner surface, like that of the stomach.

The second coat of the intestines is fleshy or muscular; and made up of two planes, one external, the other internal. The external plane is very thin, and its fibres longitudinal; the internal plane is thicker, and its fibres run transversely round the circumference of the intestinal cylinder.

The third coat is called nervosa, and is something like that of the stomach. It has a particular plane, which serves as a basis to sustain it, made up of very fine, strong, oblique fibres, which seem to be of the ligamentary or tendinous kind.

This coat sustains two reticular substances which are both vascular, one arterial, the other venal, accompanied by a great number of nervous filaments. These vessels and nerves are productions of the mesenteric vessels and nerves; and as they surround the whole canal of the intestines, some anatomists have formed them into a distinct coat, by the name of tunica vasculosa.

The nervous coat sends off from its inner surface a great number of portions of septa, more or less circular, which contribute to the formation of what are called valvæ conniventes.

The fourth or innermost coat is very soft, and is named tunica villosa. It has the same extent with the third coat, which supports it, and it lines all the septa of that third coat.

The small intestines form one continued uniform canal; and though three portions of it have three different names, yet we have no sufficient marks whereby to distinguish them, to fix the precise extent or length of each portion, to settle its just limits.

The first and shortest portion of the whole canal, is called duodenum; the second, which is much longer, jejunum; and the third, which is still longer than the second, ileum.

The duodenum having arisen from the pylorus, is immediately bent a little backward, and obliquely downward; then it bends a second time toward the right kidney, to which it is a little connected, and from thence passes before the renal artery and vein, ascending insensibly from right to left, till it gets before the aorta and last vertebrae of the back. It continues its course obliquely forward, by a gentle turn.

Through this whole course, the duodenum is firmly bound down by folds of the peritoneum, especially by a transverse duplicature which gives origin to the mesocolon.

The villi of this intestine are thicker than in the stomach; but the texture of them in man is not like hairs, as they are commonly represented in figures; but rather like that of a fungous granulated substance, composed of an infinite number of very fine papillae of different figures, in which we see, through a microscope, a multitude of depressed points or pores, by which their whole surface seems to be pierced.

By the same help we observe, on different places of the inner surface of this intestine, several round villous tubercles, rising like small verucae at different distances from each other.

This substance sustains an infinite number of capillary vessels, of different kinds; for besides the blood-vessels, we sometimes observe a great number of white filaments which run through it, and end at its inner surface, like so many capillary roots of the vessels, called venæ lacteæ.

The internal surface of the duodenum is furnished with a great number of small flat glandular tubercles, raised on the sides, and depressed in the middle, by a kind of fossula; and they are more numerous near the beginning of this intestine than any where else.

These glands appear like little bladders, with the orifices turned toward the cavity of the intestine, and the bodies fixed in the spongy substance next the nervous coat. They furnish a particular viscid fluid.

In the inner surface of the duodenum, almost at the lower part of the first incurvation, and on the shortest side, there is a longitudinal eminence, in the point or apex of which lies a particular opening, which is the orifice of the ductus biliaris, within which the ductus pancreaticus likewise opens.

INTESTINUM JEJUNUM.

THE jejunum, so called, because it is oftener found empty than the ilium, begins at the last incurvation of the duodenum, and is there connected to the beginning of the mesocolon.

From thence it bends downward from left to right, and obliquely forward, or from the vertebrae, and makes several convolutions, which lie chiefly in the upper part of the umbilical region. Through all this course it is connected to the mesentery.

The jejunum and ilium may be distinguished by dividing both intestines into five parts; and to allow nearly two fifths to the jejunum, and three fifths and a little more to the ileum.

The coats of the jejunum are nearly of the same structure with those of the duodenum, but thinner.

INTESTINUM ILEUM.

THE convolutions of the intestinum ileum surround those of the jejunum on the two lateral and lower sides, and it passes in a winding course from the left side, by the hypogastrium, to the right side, where it terminates a little below the right kidney, joining the intestina crassa.

The structure of the ileum is much the same with that of the jejunum; only the internal duplicatures or valvulae conniventes decrease gradually both in number and size.

The INTESTINA CRASSA in general, and Intestinum cæcum in particular.

THE great intestines are one continued canal, divided into three portions, like the small ones. This canal begins by a kind of sacculus or bag, which is reckoned the first of the three portions, and called cæcum. The second portion, called colon, is the longest of the three, and is distinguished from them by a great number of particular eminences or convexities, which appear on its outer surface through its whole length. The last portion is named rectum, being more uniform, narrower, thicker, and much shorter than the colon.

The structure of the great intestines is nearly the same with that of the small ones, in regard both to the number and disposition of their coats. They are shorter, and have fewer convolutions, but are much more capacious. The coats in general are stronger, but especially the muscular coat.

The intestinum cæcum is only a round short broad bag, the bottom of which is turned downward, and the mouth or opening upward. It lies under the right kidney, and is hid by the last convolution of the ileum. It is about three fingers breadth in length, and its diameter is more than double that of the small intestines.

On one side of the bottom of the cæcum lies an appendix, resembling a small intestine, nearly of the same length with the cæcum, but very slender. It is termed appendicula vermiciformis, from its supposed resemblance to an earth-worm. Its common diameter is not above a quarter of an inch. By one extremity it opens laterally, and a little obliquely, into the bottom of the cæcum; and the other extremity is closed, being sometimes greater, sometimes smaller, than the rest of the appendix.

Through the membranous or common coat of the cæcum, we see three white ligamentary bands, which adhere very closely both to the outer and muscular coat. One of them is hid by the adhesion of the mesocolon; and all the three divide the cæcum longitudinally into three parts more or less equal.

They all unite in the appendicula vermiciformis, and cover its whole outer side immediately under the common coat.

THE colon is the most considerable of all the intestines. From the cæcum, of which it is a continuation, it reaches, in form of an arch, above the umbilical region, and to the lower part of the left hypochondrium. Its continuity is however a little interrupted by the ileum, which advances into the cavity of the colon, and, together with a certain fold of that intestine, forms what is called valvula coli.

The whole convex side of the colon is divided longitudinally into three parts, by three ligamentary bands, continued from those of the cæcum, and of the same structure with these. Two of the three bands run on each side, along the great curvature of the colon; and the third along the small curvature.

These three longitudinal bands do the office of fræna, between which this intestine is through its whole length alternately depressed into transverse folds, and raised into considerable eminences. All the folds are duplicatures, which form portions of valvulae conniventes in the cavity of the intestine; and the eminences form receptacles, called the cells of the colon.

The common coat, on one side, is a continuation of the mesocolon; and, on the other side, it contributes, by the same continuation, to form the omentum.

The arch of the colon begins under the right kidney, near the haunch. It runs up on the foreside of that kidney to which it is connected, passes under the vesicula fellis, which tinges it with a yellow colour at that place, and continues its course before the first incurvation of the duodenum, to which it adheres, and partly hides it. In this part of its course, therefore, there is a remarkable connexion between the colon, duodenum, right kidney, and vesicula fellis.

From thence the arch of the colon runs before the great convexity of the stomach, and sometimes a little lower; then turns backward under the spleen, in the left hypochondrium; runs down on the foreside of the left kidney, to which it is connected; below this kidney turns toward the vertebrae, and terminates there by a double incurvation, or by two opposite convolutions, which represent in some measure an inverted roman S.

At the place where the cæcum joins the colon, one portion of the circumference of both is depressed, and forms a large fold on the inside, which advances into the cavity of the intestine. It is a little open in the middle, and its extremities are very thick, by reason of the mutual duplicature of the coats of the cæcum and colon.

The extremity of the ileum is as it were grafted in the opening of this fold, and strongly united to its sides by the adhesion of its transverse fibres to the transverse fibres of the cæcum and colon.

This union forms a pretty thick ring, which likewise advances into the common cavity of the cæcum and colon, where it is wrinkled or formed into gathers, almost like the lower extremity of the œsophagus, the pylorus or inside of the anus. Its circumference is more or less oval; and, by a kind of continuity with the com-

mon fold of the cæcum and colon, it forms two productions, which M. Morgagni calls the fræna of the valvula coli.

The membranous coat of the extremity of the ileum is continued on the cæcum and colon, without sinking into any fold, at the place where the ileum enters the colon.

This valvula coli is contrived to hinder the return of the excrements into the ileum; it produces this effect partly as a valve, and partly as a kind of sphincter.

The capacious arch of the colon is contracted by both extremities to the regio lumbaris, near the kidneys, by two particular ligaments, one on the right side, the other on the left, which are only small duplicatures of the peritoneum, more or less transverse.

The remaining portion, which forms the two convolutions in form of the roman S, contracts below the left kidney, being narrower there, than lower down. The coats of this portion become gradually thicker and stronger, and likewise the ligamentary bands, which approach each other by degrees, and seem to increase in breadth.

THE last of all the intestines, is named rectum, or the straight gut, which, properly speaking, is a true continuation of the last convolution of the colon; and it is the repository, sink, and common sewer, of the whole intestinal canal.

The rectum having passed below the last vertebra of the loins, to the inside of the os sacrum, is bent backward on that concave side to which it is connected; and having reached the os coccygis, it runs likewise in the direction of that bone, and bends a little forward, terminating beyond the extremity of the coccyx.

The figure of this intestine varies according as it is full or empty. When empty, it is irregularly cylindrical, and sinks in by a kind of transverse folds; and in that state, it is about three fingers breadth in diameter, more or less. When full, it is wider in proportion to the quantity of faeces, wind, or whatever else is contained in it; and it may be extended to the size of a large bladder, so as to represent a kind of stomach.

The membranous coat often contains a great quantity of fat, spread between it and the muscular coat, and forming round the intestine numerous eminences, in the room of the appendices adiposæ of the colon.

The muscular or fleshy coat is very thick: the longitudinal fibres, which in the other intestines are very thin, are in this stronger than the circular fibres of the rest. The ligamentary bands continue to increase in breadth, and to approach each other.

The nervous or filamentous and internal coats, are larger here, than in the other intestines; and when the rectum is empty, they form a great number of waving ridges in its cavity, which disappear, in proportion as that cavity is filled.

The innermost coat is very improperly termed villosa, and scarce deserves the name of papillaris, because of the smallness of the little corpuscles spread on its surface.

It contains a great number of single or solitary glands; and it is always moistened by a mucus of different consistences discharged by these glands or folliculi.

Near the extremity of this intestine, the rugæ or folds become in a manner longitudinal; and at last, towards the circumference of the inner margin of the anus, they form little bags or semilunar lacunæ, the openings of which are turned upward, toward the cavity of the intestine. These lacunæ are something like those at the lower extremity of the œsophagus, or upper orifice of the stomach.

At length the extremity of the rectum contracts, and terminates by a narrow orifice called the anus, the sides of which are disposed in close folds or gathers. This extremity of the intestine has several muscles belonging to it, some of which surround it like sphincters, the rest are broad fleshy planes inserted in it, and which being likewise fixed to other parts, sustain it in its natural situation, and restore it to that situation when disturbed by the force necessary for the exclusion of the feces. These latter muscles are termed levatores ani, the first go by the general name of sphincters.

These sphincters are three in number, one intestinal or orbicular, and two cutaneous or oval; whereof one is large, superior, and internal; the other small, inferior, and external.

The intestinal or orbicular sphincter of the anus, consists merely in an augmentation of the inferior portion of the fleshy fibres of the extremity of the rectum.

The cutaneous ligament goes out anteriorly, from the extremity of the os coccygis. It is very slender, and divides into two portions at the orifice of the anus, which run into the membrana adiposa, and are inserted in the skin on each side of the anus, by a kind of expansion; and continuing to divaricate, they are lost on the two sides of the peritoneum.

The interosseous ligament of the ossa pubis is a very strong triangular membrane, fixed by two of its edges in the inferior rami of these bones, all the way up to their common symphysis. The third edge, which is the lowest, is loose; and this whole membrane, the middle of which is perforated by a particular hole, is stretched very tight between the two bones, and under their cartilaginous arch, to which it adheres very closely.

At the lower part of this interosseous ligament, along its whole lower or loose edge, lies a digastric muscle, fixed by its two extremities in the rami of the ossa pubis, its middle tendon lying on the middle of the edge of the ligament.

The cutaneous sphincters have each an anterior and posterior insertion, ending both ways in a kind of point, and comprehending the orifice of the anus between their middle portions.

They are distinguished from each other by their situation, by their size, and by a kind of white cellular line. The greatest of the two appears to be double, and the smallest lies nearest the skin, and adheres most closely to it.

They are inserted backward, partly in the apex of the os coccygis, and partly in the contiguous portion of the cutaneous ligament of that bone. Forward their chief

insertion is in the middle tendon of the transversalis urethre; and they have likewise some connexions to other muscles of the urethra.

The levatores ani are broad, thin, muscular portions, fixed by one extremity of their fleshy fibres round the concave side of the inferior portion of the pelvis, from the symphysis of the ossa pubis, beyond the spine of the ischium. The other extremity of these fibres runs down on each side behind, and under the curvature of the end of the rectum, where they meet together, and unite from the basis of the os coccygis all the way to the margin of the anus.

We ought likewise to remark, that the margin or edge of the anus is formed by the union of the skin and epidermis with the internal coat of the rectum; so that the most superficial portion of that coat seems to be a continuation of the epidermis.

MESENTERIUM & MESOCOLON.

THIS great bundle of intestines is not left to move at random in the cavity of the abdomen; but artfully bound down by a membranous web, which prevents the intestinal convolutions from being intangled in each other, and from being twisted or compressed in all their different ways of meeting; and yet allows them a gentle floating, but limited motion.

This web is distinguished into two portions; one of which, being very broad and very much plaited, connects the small intestines; the other, which is long and incurvated, does the same office to the greater intestines.

These two portions are in reality only one and the same continuation of the membranous lamina of the peritoneum doubled back upon itself, and they are distinguished only by their breadth. Taken both together, they form a kind of spiral roll, more or less plaited in its circumference. The first portion has retained the name of mesentery, the other is termed mesocolon.

The mesentery begins at the last incurvation of the duodenum, and runs obliquely from left to right, along the vertebrae of the loins. In this space, the membranous portion of the peritoneum is detached on both hands, produces a duplicature by two elongations or particular laminae applied to each other, and thus forms the mesentery.

It is narrow at its upper and lower parts, but chiefly at the upper. The middle portion is very broad, and the edge of it next the intestines is every where very much plaited. These plaits or folds are only waving inflections, such as may be observed in the edge of a piece of shamoy, which has been often drawn through the fingers. They make this edge of the mesentery very long, and they run through about one third of its breadth.

The two laminae are joined together by a cellular substance, which contains glands, vessels, and nerves; and in some subjects a great quantity of fat, which keeps the two laminae a distance from each other.

Along the whole circumference of the mesentery, the two laminae are naturally separated, and applied to the two sides of the small intestines, which they invest by their union, or rather reciprocal continuation on the great curvature

curvature of that canal, and carry it as in a scarf or sling. This is what forms the external or membranous coat of the intestines.

The mesocolon is the continuation of the mesentery, which having reached the extremity of the ilium, contracts and changes its name. At this place the particular lamina which is turned to the right side, forms a small transverse fold, called ligamentum coli dextrum.

Afterwards the mesocolon ascends towards the right kidney, where it seems to be lost by the immediate adhesion of the colon to that kidney, and to the first incurvation of the duodenum. Then it appears again, and, increasing in breadth, it continues its course almost transversely under the liver, stomach, and spleen, where it begins to turn downward, under the left hypochondrium, toward the kidney on the same side.

Through this whole course, the mesocolon extends in breadth, and forms nearly a transverse semicircular plane, very little plaited at its great circumference. By this circumference or edge, it is connected to the colon; and hides that ligamentary band of this intestine, which runs along its small curvature. By its short or small edge, it forms the triangular case of the duodenum; and by its great edge, the external coat of the colon, in the same manner as the mesentery does that of the small intestines. As it passes under the large extremity of the stomach, it adheres a little to the lower portion of that extremity, as the diaphragm does to the upper.

Having got below the left kidney, it contracts and forms another transverse fold, called ligamentum coli sinistrum. Afterwards it expands again, but not so much as in the upper part, and runs down on the left psoas muscle, toward the last vertebrae of the loins. This descending portion is fixed to the convolutions of the colon in the same manner as the superior portion is to the arch of that intestine.

The intestinum rectum is likewise invested by a particular production of the peritoneum, called commonly by the barbarous name of mesorectum. This production is very narrow; and, about the middle of the foreside of the rectum, it forms a transverse semicircular fold, which appears when the intestine is empty, but is lost when it is filled.

GLANDULÆ MESENTERICÆ, VASA LYMPHATICA & LACTEA.

BETWEEN the laminae of the mesentery, a great number of glands lie scattered through the cellular substance. In the natural state, these glands are something of the figure of lentils or little round beans; some of them being orbicular, others oval, but all of them a little flattened.

These glands are of the number of those that anatomists call glandulae conglobatae, the structure of which is not as yet sufficiently known. They seem to be of a cellular substance, surrounded by a very fine membrane or coat, on which, by the help of microscopes, we discover an intertexture of particular filaments.

Besides the blood-vessels which are distributed in a reticular manner in the mesenteric glands, and besides many nervous filaments spread through them, we dis-

cover an infinite number of small vessels of another kind running from gland to gland.

These vessels are extremely thin and transparent, and furnished on the inside with numerous valves, which appear on the outside like little small knots very near each other. They go out from each gland by ramifications, as by so many roots, and having formed a small trunk, they are again divided, and enter some neighbouring gland by the same kind of ramifications by which they went out from the former.

They are termed lymphatic vessels, because for the most part they contain a very clear, limpid, though mucilaginous serum, called lympha by anatomists. But as they have likewise been observed to be filled with a white milky fluid, called chyle, they have been called vasa chylosifera, or vena lactea. They have the name of veins, because their valves are disposed as those of the ordinary blood-veins, and because the fluid which they contain runs from smaller into larger tubes.

They derive their first origin from the tunica villosa of the intestines, and chiefly from that of the small intestines, by a great number of small capillary roots. From these roots there arises, between the coats of the intestines, a kind of rete mirabile, which surrounds almost the whole circumference of the intestinal canal, between the muscular and external coat.

This reticular texture of lacteal vessels keeps close to the external coat, and leaves the canal along with it, on the side of the mesentery, where it forms two planes of ramifications, plainly distinguished from each other by the cellular substance, and adhering closely to the inside of the two membranes of the mesentery. In this separate state they run on the laminae of the mesentery, as far as the first mesenteric glands, where they unite again into one plane.

After this union, the lacteal vessels are distributed almost uniformly through the whole extent of the mesentery, from its circumference to its origin or adhesion to the vertebrae of the back, between the mesenteric glands, which they join, and form frequent anastomoses or communications.

Having passed through the mesentery, the ramifications begin to unite as they approach the spina dorsi, and consequently their number is lessened, and their size increased; and having passed the last mesenteric glands, they terminate about the middle of the adhesion of the mesocolon in small common trunks, which receive a great number of lymphatic vessels from the glandulae lumbares, and others below these.

The lacteal vessels which lie between the mesenteric glands and middle adhesion of the mesocolon to the spina dorsi, run down on the body of the inferior aorta, between the extremities of the small muscle of the diaphragm, and terminate in a kind of cistern, called by some receptaculum chyli, by others receptaculum Pecqueti.

The greatest part of the receptaculum chyli lies behind the right portion of the inferior muscle of the diaphragm, on the right side of the aorta, at the union of the last vertebra of the back with the first of the loins. It is a kind of membranous vesicle, the conformation of which is various in human subjects. Sometimes it is of

an uniform long oval figure, like the vesicula fellis; sometimes it is divided by strictures, into several small roundish bags more or less flattened, and sometimes it surrounds the trunk of the aorta like a collar.

It is composed of very thin coats, and its cavity is divided by small pelliculæ or membranous septa, the disposition of which is irregular. It is chiefly round the lower part of this receptacle, that the last lacteal vessels are inserted, some on the sides, and some behind the aorta; and they are accompanied by numerous lymphatic vessels. The upper portion is contracted between the aorta and vena azygos, and forms a particular canal, which runs up through the thorax, by the name of ductus thoracicus.

HEPAR & VESICULA FELLIS.

THE liver is a large and pretty solid mass, of a dark red colour, a little inclined to yellow, situated immediately under the arch of the diaphragm, partly in the right hypochondrium, which it fills almost intirely, and partly in the epigastrium, between the appendix ensiformis and spina dorsi, and terminating commonly in the left hypochondrium.

The figure of the liver is irregular, it being arched or convex on the upper part, unequally concave on the lower, and very thick on the right and back sides. Towards the left and anterior sides its thickness decreases very much, and terminates there by a kind of edge; and it is broader from right to left, than from before backwards.

It may be divided into lateral parts called lobes; one of which is termed the great or right lobe; the other, the small or left lobe. These two lobes are distinguished above, by a membranous ligament; and below very plainly, by a considerable scissure lying in the same direction with the superior ligament.

The eminences on the concave side of the liver belong to the great lobe. The principal eminence is a sort of triangular or pyramidal apophysis situated backward near the great scissure which distinguishes the two lobes.

This triangular eminence is termed lobulus Spigelii, or simply the small lobe of the liver. One of its angles advances a considerable way toward the middle of the lower side of the great lobe, and is lost there. Toward the foreside, there is another eminence less prominent but broader; and to this eminence and the former, the ancients gave the general name of porta.

The depressions on the concave or lower side of the liver are four in number. The first is the scissure that separates the two lobes, which runs across the concave side, from the eminences already mentioned, to the anterior edge, where it terminates by a notch of different depths in different subjects. This is termed the great scissure of the liver.

The second depression is situated transversely between the two eminences of the great lobe, and filled by the sinus of the vena portæ. The third depression is backward, between the great lobe and lobulus Spigelii, and the vena cava passes through it. The fourth is a kind of sulcus between the lobulus and small lobe of the liver, which in the fetus served to receive a venal canal lost in

adults, in whom it appears only as a kind of ligament. This sulcus is in some measure a continuation of the great scissure, and joins the vena cava by an acute angle.

Besides these four depressions, there is one on the fore-part of the great lobe, in which the vesicula fellis is lodged; and it sometimes runs as far as the edge, where it forms a small notch. We may likewise reckon among these depressions, a small superficial cavity in the posterior and lateral part of the lower side of the great lobe, by which it rests on the right kidney; and likewise a superficial cavity in the left lobe, where it runs over the stomach.

Lastly, on the posterior edge of the liver, there is a great sinus common to both lobes, which gives passage to the spina dorsi and œsophagus, near the place where the vena cava descends.

The convex side of the liver is commonly connected to the diaphragm by three ligaments, which are only continuations of the membranous lamina of the peritoneum. One lies near the edge of the extremity of each lobe, and one in the middle, and they are accordingly termed the right, middle, and left ligaments. There is a cellular substance in the duplicature of each, in which the blood-vessels and lymphatics run, and which sends off a kind of lamina into the substance of the liver.

The right ligament sometimes connects the great lobe to the cartilages of the false ribs; and the left ligament, or that of the small lobe, is often double, and advances toward the middle ligament. This middle ligament begins low, in the great scissure of the liver, near the eminences called portæ, and from thence passes thro' the anterior notch and over the convex side of the liver at the union of the two lobes, and is fixed obliquely in the diaphragm.

It is likewise fixed along the upper and inner part of the vagina of the right musculus rectus of the abdomen, in such an oblique manner as to be nearer the linea alba below than above.

Besides these ligaments the great lobe of the liver is likewise connected to the right ala of the tendinous portion of the diaphragm, not by a ligament, but by a broad and immediate adhesion, without the intervention of the membrane of the peritoneum, which is only folded quite round this adhesion, to form the external membrane of all the rest of the body of the liver.

The middle ligament, called improperly ligamentum hepatis suspensorium, contains in its duplicature a thick white rope, like a round ligament, which was the umbilical vein in the fetus. Thus the lower part represents a falx, the convex edge of which is sharp, and the other rounded.

All these ligaments serve to keep the liver in its proper situation, and to hinder it from inclining too much towards either side: But we must not imagine that any of them serve to suspend it; because it is sufficiently supported by the stomach and intestines, especially when they are filled.

When the stomach is empty, or when we fast longer than ordinary, it is a common expression to say the stomach pinches us. As the liver is not then sustained by the stomach and intestines, it descends by its own weight, and

Fig. 1.

This central figure, labeled Fig. 1, is a detailed anatomical illustration of the human brain and spinal cord. The brain is shown from a superior view, with the cerebral hemispheres (labeled A) and cerebellum (labeled B) visible. The spinal cord (labeled K) extends downwards from the brain, showing the vertebral column (labeled L). A complex network of nerve roots (labeled 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25) is depicted, branching out from the spinal cord. The diagram is highly detailed, showing the intricate connections between the brain, spinal cord, and peripheral nerves.

Fig. 2.

This figure, labeled Fig. 2, shows a lateral view of a brain lobe. The lobe is labeled A, and the cerebellum is labeled B. A series of nerve roots (labeled 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13) are shown emerging from the lobe. The diagram is labeled with letters A, B, C, D, E, F, G, H, I, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z.

Fig. 3.

This figure, labeled Fig. 3, shows a lateral view of a brain lobe. The lobe is labeled A, and the cerebellum is labeled B. A series of nerve roots (labeled 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13) are shown emerging from the lobe. The diagram is labeled with letters A, B, C, D, E, F, G, H, I, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z.

Fig. 4.

This figure, labeled Fig. 4, shows a lateral view of a brain lobe. The lobe is labeled A, and the cerebellum is labeled B. A series of nerve roots (labeled 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13) are shown emerging from the lobe. The diagram is labeled with letters A, B, C, D, E, F, G, H, I, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z.

Fig. 5.

This figure, labeled Fig. 5, shows a lateral view of a brain lobe. The lobe is labeled A, and the cerebellum is labeled B. A series of nerve roots (labeled 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13) are shown emerging from the lobe. The diagram is labeled with letters A, B, C, D, E, F, G, H, I, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z.

Faint botanical illustration of a plant part, possibly a leaf or stem, with some illegible text above it.

Faint botanical illustration of a plant part, possibly a leaf or stem, with some illegible text above it.

Faint botanical illustration of a plant part, possibly a leaf or stem, with some illegible text above it.

Faint botanical illustration of a plant part, possibly a leaf or stem, with some illegible text above it.

Faint botanical illustration of a plant part, possibly a leaf or stem, with some illegible text above it.

Fig. 1.

Fig. 2.

Fig. 3.

Fig. 4.

Fig. 5.

and chiefly by the means of the middle ligament pulls the diaphragm along with it. It is in that place therefore that we have this uneasy sensation, and not at the superior orifice of the stomach, as is commonly believed.

The liver is composed of several kinds of vessels, the ramifications of which are multiplied in an astonishing manner, and form by the intertexture of their capillary extremities, an innumerable collection of small pulpy, friable corpuscles, which are looked upon to be so many organs designed to separate from the mass of blood a particular fluid termed the bile.

The greatest part of these vessels from one end to the other is included in a membranous vagina called capsula vena portæ, or capsula Glissoni.

The trunk of the vena portæ is situated transversely between the broad anterior eminence of the great lobe of the liver, and the root of the lobulus, in a particular scissure, and forms what is called the sinus of the vena portæ. From this sinus five principal branches go out, which are afterwards divided into millions of ramifications through the whole substance of the liver.

At this place the vena portæ lays down the common office of a vein, and becomes a kind of artery as it enters, and is again ramified in the liver. The extremities of all these ramifications of the trunk of the vena portæ hepatica end in the pulpy friable corpuscles which seem to be thick villous folliculi.

Its in these folliculi that the bile is secreted, and it is immediately collected in the same number of extremities of another kind of vessels, which unite by numerous ramifications into one common trunk. These ramifications are termed pori biliarii, and the trunk ductus hepaticus; and the ramifications of these two kinds of vessels are invested together by the capsula of the vena portæ.

The blood, deprived of this bilious fluid, is reconveyed to the heart by a great number of venal ramifications, which afterwards unite into three principal branches, besides others that are less considerable, that terminate in the vena cava, and are all called by the name of vena hepatica.

The capillary extremities of the ramifications of the vena cava, join those of the vena portæ, and accompany them through the liver; and yet the great branches of both veins intersect each other in several places.

The ductus hepaticus, or trunk of the pori biliarii, having run a little way, joins another canal called ductus cysticus or vesicularis, because it comes from the vesicula fellea. These two united ducts form a common trunk named ductus cholidochus, because it conveys the bile. This duct having reached the incurvation of the duodenum, insinuates itself through the coats of that intestine, and opens into the cavity thereof, not by a round papilla, but by an oblong orifice, rounded at the upper part, and contracted at the lower, like the spout of an ewer, or like a common tooth-picker.

The gall-bladder is a kind of small bag shaped like a pear, that is, narrow at one end and wide at the other. The wide extremity is termed the fundus or bottom, the narrow extremity the neck, and the middle portion the body. About one third of the body of the vesicula lies in a depression on the concave side of the liver, from

the trunk or sinus of the vena portæ, where the neck is situated to the anterior edge of the great lobe, a little toward the right side, where the bottom is placed.

The gall-bladder is composed of several coats; the outermost of which is a continuation of that which invests the liver, and consequently of the peritoneum.

The second coat is fleshy, and made up of two strata, one longitudinal, the other transverse, the fibres of which have nearly the same irregular direction with those of the stomach; and this disposition of the fibres in these viscera is owing to the different diameters in the several portions of them, and to their incurvation.

These two coats are connected by a cellular substance continued between the body of the vesicula and the liver, all the way, to a whitish stratum, which is looked upon as the third coat of the gall-bladder answering to the tunica nervosa of the intestines.

The innermost or fourth coat has on the inside a great number of reticular folds, filled with small lacunæ, like perforated papillæ, especially near the neck of the vesicula where these folds are longitudinal, and afterwards form a kind of small pylorus with plaits of the same nature with those in the great one. These lacunæ are looked upon to be glands.

That side of the body of the vesicula which lies next the liver is connected to that viscus by a vast number of filaments, which run a great way into the substance of the liver; and among these filaments there are some ducts which form a communication between the pori biliarii and vesicula. They are most numerous near the neck of the vesicula, and they are named ductus cysto-hepatici, or hepatico-cystici.

The neck of the vesicula is formed by the contraction of the small extremity; and this neck bending afterwards in a particular manner, produces a narrow canal named ductus cysticus.

The neck of the vesicula is nearly of the same structure with the other parts. It has on the inside several reticular rugæ and some folds which appear like fragments of valvular conniventes, situated very near each other, from the neck to the contraction of the cystic duct. The first of these folds is pretty broad and large, and almost circular; the next is more oblique, and smaller in size; and the rest diminish in the same manner.

The bile which passes through the ductus hepaticus into the cholidochus, may be called hepatic; and that which is collected in the vesicula fellea, may be termed cystic. The hepatic bile flows continually through the ductus cholidochus into the duodenum, whereas the cystic bile flows only by reason of plentitude or by compression.

The uses of the liver shall be explained after the description of pancreas, spleen, and omentum, all these viscera having a great relation to the liver.

PANCREAS.

The pancreas is a long flat gland, of that kind which anatomists call conglomerate, situated under the stomach, between the liver and the spleen. Its figure resembles that of a dog's tongue; and it is divided into two sides, one superior, the other inferior; two edges, one ante-

rior, the other posterior; and two extremities, one large, which represents the basis of a tongue, and one small and a little rounded like the point of a tongue.

The pancreas is situated transversely under the stomach, in the duplicature of the posterior portion of the mesocolon. The large extremity is connected to the first incurvation of the duodenum, and from thence it passes before the rest of that intestine, all the way to its last incurvation; so that a great part of the duodenum lies between the pancreas and the vertebrae of the back. The small extremity is fixed to the omentum near the spleen.

The pancreas is composed of a great number of soft glandular molecules, combined in such a manner, as to exhibit the appearance of one uniform mass on the outside, the surface of which is rendered uneven only by numerous small convexities, more or less flattened. When these molecules are separated a little from each other, we find along the middle of the breadth of the pancreas, a particular duct, in which several smaller ducts terminate laterally on each side, like small rami in a stem.

This canal, named ductus pancreaticus, or ductus Virsangi, is very thin, white, and almost transparent, and the extremity of the trunk opens commonly into the extremity of the ductus cholidochus. From thence it diminishes gradually, and terminates in a point, next the spleen. The small lateral branches are likewise pretty large near the trunk, and very small toward the edges of the pancreas; all of them lying in the same plane like the branches of the common fem.

The pancreatic duct is sometimes double in man, one lying above the other. It is not always of an equal length, and sometimes runs in a winding course, but always in the same plane; and it is nearer the lower than the upper side of the pancreas. It pierces the coats of the duodenum, and opens into the ductus cholidochus, commonly a little above the prominent point of the orifice of that canal; and sometimes it opens immediately into the duodenum.

S P L E E N.

THE spleen is a bluish mass, something inclined to red, and of a long oval figure, being about seven or eight fingers-breadth in length, and four or five in breadth. It is of a softish substance, and is situated in the left hypochondrium, between the great extremity of the stomach, and the neighbouring false ribs, under the edge of the diaphragm, and above the left kidney.

The inner or concave side is divided by a longitudinal groove or scissure, in two planes or half-sides, one upper, the other lower; and by this groove, the vessels and nerves enter in human subjects. The superior half-side is broader and more concave than the inferior, being proportioned to the convexity of the great extremity of the stomach. The inferior half-side lies backward on the left kidney, and forward on the colon; and sometimes this side of the spleen appears to have two superficial cavities, one answering to the convexity of the stomach, the other to that of the colon. The convex side of the spleen is turned to the left ribs.

It is connected to the stomach, by the vessels called vasa brevia; to the extremity of the pancreas, by ramifications of the splenic artery and vein; and to the omentum, by ramifications which the same artery and vein send to the spleen, and which run in the longitudinal groove.

It is connected to the edge of the diaphragm by a particular membranous ligament of different breadths in different subjects, fixed in its convex side, sometimes near the upper edge, and sometimes near the lower.

The structure of the spleen is not easy to be unfolded in man, and it is very different from that of the spleens of brutes, from which both public and private demonstrations are commonly made.

Its coverings adhere to it so closely in man, that it is difficult to distinguish the common from the proper coat; whereas in some brutes, such as oxen, sheep, &c. we easily find two coats separated by a cellular substance. This covering seems to be no otherwise a continuation of the peritoneum than by the intervention of the omentum and mesocolon.

In man the substance of the spleen is almost wholly vascular. In oxen the substance of the spleen is chiefly reticular, and in sheep it is cellular. In oxen and sheep there are no venal ramifications, but instead thereof only open sinuses disposed like branches, except a small portion of a venal trunk perforated on all sides, at the extremity of the spleen.

In the human spleen we see something like glandular corpuscles, as in those of other animals; and there are numerous venal ramifications through its whole extent. Between these ramifications we every where observe an appearance of extravasated blood, lying in a kind of filamentary transparent and very delicate substance expanded through the whole spleen.

This filamentary substance, having surrounded all the ramifications, terminates in almost imperceptible cells which communicate with each other.

OMENTUM & APPENDICES EPIPLORICÆ.

THE omentum is a large, thin, and fine membranous bag, surrounded on all sides by numerous portions of fat, which accompany and even invest the same number of arteries and veins adhering closely to each other.

The greatest part of it resembles a kind of flat purse or a sportsman's empty pouch, and is spread more or less on all the small intestines from the stomach to the lower part of the regio umbilicalis. Sometimes it goes down to the lower part of the hypogastrium, and sometimes does not reach beyond the regio epigastrica. It is commonly plaited or folded in several places, especially between the bands of fat.

It is divided into a superior and inferior, an anterior and posterior, and a right and left portion. The superior portion is in a manner divided into two borders, one of which is fixed along the great curvature or convex side of the arch of the colon, and the other along the great curvature of the stomach. The commissure or union of these two borders on the right side, is fixed to the common ligament or adhesion of the duodenum and colon.

colon, and to the contiguous parts of these intestines. That on the left side is fixed to the longitudinal scissure of the spleen, to the extremity of the pancreas, and to the convex side of the great extremity of the stomach. It is likewise fixed to the membranous ligament which sustains the ductus cholidochus, and connects it to the vena portæ ventralis.

Below these adhesions, the other portions, that is, the anterior, posterior, two lateral and inferior portions, which last is the bottom of the fœculis epiploicus, have commonly no fixed connections, but lie loose between the fore-side of the cavity of the abdomen and intestines.

The membrane of the omentum is through its whole extent made up of two extremely thin laminae joined by a cellular substance; the quantity of which is very considerable along the blood-vessels, which it every where accompanies in broad bands, proportioned to the branches and ramifications of these vessels. These cellular bands are more or less filled with fat according to the corpulence of the subject.

Besides this large membranous bag, there is another much smaller, which differs from the large one, not only in size, but also in figure, situation and connexion; and this is the little omentum. This small bag is fixed by its whole circumference, partly to the small curvature of the stomach, and partly to the concave side of the liver before the sinus of the vena portæ, so as to surround and contain the prominent portion of the lobulus.

The little omentum is thinner and more transparent than the other, and its cavity diminishes gradually from the circumference to the bottom. Its structure is pretty much the same with that of the great omentum, it being composed of two laminae, with a mixture of the same portions of fat, which are considerably finer than in the other.

The fatty appendices of the colon and rectum appear to be a kind of small omenta or appendices epiploice. They are situated at different distances along these intestines, being particular elongations of their common or external coat. They are of the same structure with the great omenta, and there is a cellular substance contained in their duplicature, more or less filled with fat, according as the subject is fat or lean.

Uses of the Abdominal Viscera.

THE intestines in general finish what the stomach had begun. The alimentary pulp having been sufficiently prepared by the fœcus gastricus, or lymph of the stomach, undergoes a further change by the intestinal lymph, bile, and pancreatic juice, by which the milky liquor called chyle is produced, and this liquor rendered fluid enough to enter the lacteal vessels through the tunica villosa of the small intestines, while the grosser portion of the aliment continues its course, and becoming gradually thicker as it advances toward the great intestines, is there collected by the name of fæces.

The valve of the colon, which might more properly be termed sphincter or pylorus of the ileum, hinders the fæces from returning into the small intestines.

The glandular lacunæ of the intestines furnish conti-

nually a kind of mucilage, which not only defends the internal coat from the acrimony of the fæces, but serves also to lubricate these fæces in proportion to their different degrees of solidity.

The intestinum rectum is the last reservoir of the fæces. The great thickness of its muscular coat, and the great number of longitudinal fibres by which this thickness is chiefly formed, enable it to yield to the collected fæces to so great a degree, as to represent a large bladder or stomach. The musculi levatores ani serve to suspend the lower portion of this intestine, especially when full; and it is partly by the contraction of these muscles which overcome the sphincter of the anus, that the fæces are discharged out of the body. These sphincters form the third pylorus of the whole alimentary canal.

The mesentery and mesocolon connect the intestines, in such a manner, as that they cannot be twisted or run into knots, without hindering them from sliding and yielding to each other according to the different postures of the body, or according as they are more or less empty or full.

The adhesions of the mesentery form the convolutions of all the small intestines into a large bundle, irregularly round, which fills a great part of the cavity of the abdomen, from the epigastrium downward.

The mesocolon by its adhesion to the colon forms a kind of septum transversum, between the small intestines and the viscera contained in the epigastrium; and this septum supports the liver and stomach under the arch of the diaphragm, just as much as it is sustained by the intestines.

The breadth of the mesentery and mesocolon affords a large extent to the ramifications of the arteries, veins, and nerves, distributed through them by innumerable communications and anastomoses, by means of which any portion of the intestines may be supplied, though the principal branch which leads to it should happen to be compressed or obstructed.

The cellular substance in the duplicature of the mesentery and mesocolon, serves not only for a soft bed to all these ramifications, but also to contain those collections of fat necessary for the formation of the bile; and the cellular substance of the mesentery has likewise one use peculiar to it, which is to invest the lymphatic glands and lacteal vessels, and upon this account it is thicker than that of the mesocolon.

The lacteal vessels being first formed by a copious reticular texture round the circumference of the intestines, resembling the vascular network of that canal, and afterwards uniting every where through the duplicature of the mesentery, with the arterial ramifications which they likewise accompany in many places; it is easy to conceive, that the pulsation of the mesenteric arteries must propel the chyle in the lacteal vessels from the intestines to the receptaculum chyli, that motion being suitable to the direction of their valves.

The liver is the principal organ for the secretion of the bile. The villi of that immense number of glandular cells of which it is composed, filtrate continually from the blood of the vena portæ small drops of bile, which afterwards insinuate themselves into the pori biliarii, and

are in part lodged in the vesicula fellis, and in part run directly into the duodenum.

The spleen, omentum, appendices epiploicæ, adipose strata of the mesentery, and those of the great intestines, and even the pancreas, with the whole series of glands in the intestinal canal, seem to contribute to the formation of the bile, as so many auxiliary or rather preparatory organs.

The vesicular bile appears to be more exalted than that in the hepatic duct; and by meeting in the ductus cholidochus, they seem to compose a third kind of bile, which without the cystic or vesicular bile would perhaps be too mild, and too acrid without the hepatic. This bile mixes in the duodenum with the pancreatic juice, and with that of the intestinal glands; and from this mixture a fluid results, which is proper to separate the chylous matter from the gross and useless part of the alimentary pulp, as it comes from the stomach.

RENES & URETERES.

THE kidneys are two pretty solid, glandular bodies, situated in the posterior part of the cavity of the abdomen, on each side of the lumbar vertebrae, between the last false ribs and ossa ileum. The right kidney lies under the great lobe of the liver, and is consequently lower than the left, which lies under the spleen.

The figure of the kidneys resembles that of a large bean, their circumference being convex on one side, and concave on the other. The concave side is turned to the vertebrae, and the convex side the opposite way.

In each kidney we observe a fore and back side, an upper and lower extremity, a great and small curvature, and a convexity and concavity.

The back-side is broader than the fore-side; and the upper extremity is a little broader and more incurvated than the lower. The depression in the small curvature is oblong and uneven, resembling a sinus, surrounded by several tubercles; and as it is turned a little toward the fore-side, this side is something narrower than the other.

The kidneys are surrounded by a very loose membranous and cellular covering, called membrana adiposa, because in fat persons the cells of this substance are filled with fat.

The proper coat or membrane of the kidneys is composed of two laminae, between which there is likewise a very fine cellular substance, which may be made sensible by blowing through a pipe between the two laminae.

The external lamina is very thin, and adheres closely to the internal lamina, by means of the cellular substance. The internal lamina penetrates every where, by numerous elongations, into the substance of the kidney, from which it cannot be separated without tearing.

The surface of the external lamina is very smooth, polished and glistening, and it renders the whole surface of the kidney very even and uniform.

The blood-vessels having entered the kidneys, are ramified every way; and these ramifications send out other capillary rami, which go all the way to the surface, where they appear like irregular stars, and furnish the proper membrane of the kidneys.

The proper membrane having surrounded the kidney all the way to the sinus, joins the vessels at that place, and accompanies all their ramifications through the body of the kidney, in form of a vagina or capsula.

We may distinguish three kinds of substances in the kidney; an exterior substance, which is thick, granulated, and in a manner cortical; a middle substance, which is medullary and radiated, called striata, sulcata, or tubularis, because it seems to be made up of radiated tubes; and an inner substance, which is only a continuation of the second, and terminates on the inside by papillæ, for which reason it is called papillaris.

The papillæ, which are only a continuation of the medullary substance, are often a little paler than that substance. They are ten or twelve in number, very distinct from each other, resembling the same number of cones, with very broad bases and obtuse apices.

At the point of each papilla we see, even without a microscope, in a small depression, several very small holes, through which little drops may be perceived to run when the papillæ are compressed. These are little drops of urine, which being filtrated, partly in the cortical, partly in the medullary or tubular substance, do afterwards pass through the substance of the papillæ, and are discharged by these orifices.

Each papilla lies in a kind of membranous calix or infundibulum, which opens into a common cavity called the pelvis. This pelvis is membranous, being of the same structure with the calices, of which it is a continuation; and its cavity in man is not uniform, but distinguished into three portions, each of which contains a certain number of infundibula or calices, together with the papillæ which lie therein.

At the place where these infundibula surround the bases of the papillæ, they send productions into the medullary or radiated substance of the kidney, which accompany the blood-vessels, and serve for capsule or vagina to all the vascular arches, both arterial and venal, and to their different ramifications, quite through the cortical substance, and as far as the surface of the kidney.

After the infundibula have contracted in a conical form round the apices of the papillæ, each of them forms a small short tube or gullet, which, uniting at different distances along the bottom of the sinus of the kidney, form three large tubes, which go out from the sinus in an oblique direction from above downwards, and immediately afterwards unite into one trunk.

This trunk becomes a very long canal, called the ureter. In men the three tubes supply the place of what is called the pelvis in brutes, and might properly be called the roots or branches of the ureters than the pelvis. The ureters are commonly two in number, one for each kidney.

The situation of the trunk, and of the roots and branches of each ureter, with respect to the renal artery and vein, is in the following manner: The artery is in the upper part of the sinus, and partly before the vein. The vein is about the middle, and between the artery and ureter. The ureter is in the lower part, a little behind the vein, and it is partly surrounded by one branch of the artery.

From

The ureters run down obliquely, and with a very small degree of inflection, from the kidneys to the lateral parts of the inner or anterior side of the os sacrum, and passing between the rectum and bladder they terminate in the last of these viscera.

They are composed of three proper coats; the first of which, that surrounds the rest, is of a whitish colour, and of a very compact filamentary texture, being stretched with difficulty, and appearing like a filamentary substance degenerated. The next coat is of a reddish colour, stronger than the first, and made up of different strata of fibres, which intersect each other; but it is very hard to determine, whether they are muscular, or simply membranous.

GLANDULÆ RENALES, vulgo CAPSULÆ ATRIBILARIÆ.

IMMEDIATELY above each kidney, lies a glandular body, called by the ancients capsulæ atribilarie; by others capsulæ renales, renes succenturiati, and glandulæ renales. They are situated on the upper extremity of each kidney a little obliquely, that is, more toward the inner edge and sinus of the kidney than toward the outer convex edge.

Each gland is an oblong body with three sides, three edges, and two points, like an irregular crescent with its great or convex edge sharp, and the small concave edge broad. Its length is about two thirds of the greatest breadth of the kidney, and the breadth of its middle portion is about one third of its extent between the two extremities, sometimes more, sometimes less. Its colour is a dark yellow.

It has one anterior, one posterior, and one lower side, which last may be termed the basis; and it has one upper, and two lower edges, whereof one is anterior, the other posterior. The upper edge may be called the crista, and the two lower edges the labia.

The surface of these glands is uneven; the foreside is the broadest, and the lower side or basis the narrowest. Along the middle of the anterior side, a ridge runs from the edge of the inner extremity, a little above the basis, to the point of the other extremity, and divides this side into two equal parts, like the middle rib of the leaf of a tree; and on the lower side, under the basis, there is a kind of raphe or suture.

The blood vessels of these glands come from the arteries, and venæ renales, and diaphragmaticæ, and likewise from the aorta and vena cava, from the arteria cæliaca, &c. These vessels are termed the capsular arteries and veins; and as they enter the glands, they seem to be invested by a vagina.

In the inside of these capsulæ, there is a narrow triangular cavity, the surface of which is full of short strong villi of a yellowish colour; but in children it is reddish, and of a dark brown in aged people. The sides of this cavity are connected by a great number of filaments; and they appear to be wholly glandular, that is, to be filled with very fine small folliculous corpuscles.

This cavity contains an unctuous viscid liquor, of a yellowish red colour, which with age changes gradually

into a yellowish purple, a dark yellow, and a black yellow; and sometimes it is perfectly black; but even then, if it be spread thin on a large surface, it appears yellow.

The uses of these renal glands have not as yet been discovered; and all that we know about the liquor contained in them, is, that it resembles the bile. They are very large in the fetus, and diminish in adults.

VESICA URINARIA.

THE bladder is a kind of membranous and fleshy pouch or bottle, capable of dilatation and contraction, situated in the lower part of the abdomen, immediately behind the symphysis of the ossa pubis, and opposite to the beginning of the intestinum rectum. The figure of it is nearly that of a short oval. It is broader on the fore and back sides, than on the lateral parts; rounder above than below when empty, and broader below than above when full.

It is divided into the body, neck, and bottom; into an anterior, posterior, and two lateral parts. The upper part is termed the fundus or bottom; and the neck is a portion of the lower part, which is contracted like the gullet of some vessels.

The bladder is made up of several coats. That part of the external coat which covers the upper, posterior and lateral sides of the bladder, is the true lamina or membrane of the peritoneum; and the rest of it is surrounded by a cellular substance, by the intervention of which, the peritoneum is connected to the muscular coat.

The proper coats are three in number, one muscular, one nervous, and one villous, which is the innermost. The muscular coat is composed of several strata of fleshy fibres; the outermost of which are mostly longitudinal; the next to these are more inclined toward each hand; and the innermost, more and more oblique; and they become at length almost transverse.

The nervous coat is nearly of the same structure with the tunica nervosa of the stomach.

The internal coat is something granulated and glandular, and a mucilaginous serum is continually discharged through it, which moistens the inner surface of the bladder and defends it against the acrimony of the urine.

At the top of the bladder, above the symphysis of the ossa pubis, we observe a ligamentary rope, which runs up between the peritoneum and the linea alba of the abdomen, all the way to the navel, diminishing gradually in thickness as it ascends. This rope had a particular use in the fetus, as shall be said in another place. It is sufficient to add here, that it is in part originally a production of the inner coats of the bladder, which production is termed urachus.

This rope is composed likewise of two other ligamentary elongations, which are the extremities of the umbilical arteries. These arteries come from the hypogastricæ, run up by the sides of the bladder, and remain hollow and filled with blood, even in adults, as high as the middle of the bladder, through all which space they likewise send off ramifications. Afterwards they lose their cavity, and become ligamentary as they ascend.

At the upper part of the bladder, they approach each other; and, joining the urachus, form that rope, which may be termed the superior ligament of the bladder.

The lower part of the bladder, which deserves the name of fundus much better than the upper part, is perforated by three openings, one anterior, and two posterior. The anterior opening is formed by an elongation of all the proper coats, in form of a gullet, turned much in the same manner with the inner orifice of the rostrum of the head of an alembic. This elongation is called the neck of the bladder, the description of which belongs to that of the parts of generation in men.

The other two openings in the true fundus of the bladder, are formed by the ureters, which, in their course downward already described, run behind the spermatic vessels, and then behind the lower part of the bladder, approaching each other. Each ureter lies between the umbilical artery and vas deferens of the same side, the artery lying on the outside of the ureter, and the vas deferens on the inside.

Afterwards they get between the vasa deferentia and the bladder, crossing these canals: and then at about a finger's breadth from each other, they begin to pierce the coats of the bladder. They run a little way between the muscular and nervous coats, and open into the bladder obliquely, something nearer each other than when they first entered its coats.

The orifices of the ureters in the bladder, are something oval, and narrower than the cavity of the ureters immediately above them. The edge of these orifices is very thin, and seems to be formed merely by the union of the internal coat of the bladder with that of the ureters.

Besides the ligaments already mentioned, there are likewise two small ones, by which the anterior part of the true fundus of the bladder is connected to the ossa pubis, which shall be described with the neck and sphincter after the history of the parts of generation in both sexes.

THE PARTS OF GENERATION IN MALES.

The spermatic arteries go out most commonly from the anterior part of the inferior aorta, near each other, and about an inch lower than the arterie renales.

They run down obliquely in the posterior part of the abdomen, within the cellular substance of the peritoneum, passing insensibly from behind forward; and so parting gradually more and more from the aorta, they cross over the foreside of the ureters, and run through the openings or rings of the abdominal muscles, along with the elongations or productions of the cellular portion of the peritoneum.

They are small at their origin; and in their course downward, they give off pretty considerable lateral ramifications to the membrana adiposa, peritoneum, and also to the mesentery.

They sometimes pass through the areolæ, or meshes of the spermatic veins; and before they go out of the abdomen, they are divided into very fine rami, which run

in a more or less winding course, almost parallel to each other.

Afterwards they enter the cellular productions of the peritoneum, which serve them for vaginae. They do not fluctuate indifferently from one side to the other of these vaginae; but are connected along their inner surface by thin membranous laminae, which are likewise continuations of the cellular substance of the peritoneum.

The arteries continue the same winding course within these vaginae, passing before the vasa deferentia, which are likewise contained in them; and at length they terminate by ramifications in the epididymes and testes.

The testes are two glandular bodies, situated near each other, without the abdomen, below the interstice between the groins in an adult. The ancients named them didymi or gemini. Their size is nearly that of a pigeon's egg, and they are of an oval figure, a little flattened at each side. We may consider in each testicle, two extremities, two edges, and two sides. One extremity is situated forward, and a little upward; the other backward, and a little downward; and their edges lie upward and downward.

At the upper edge, they have each an appendix, called epididymis, together with which it is involved in several coverings; and they are both suspended in a common covering, called the scrotum.

Each testicle is a spermatic gland formed by a vast number of fine whitish tubes, folded and twisted in different manners, and distributed in different fasciculi, between membranous septa; the whole being surrounded by a strong common covering, named tunica albuginea.

These septa are disposed longitudinally, divaricating from each other on one side, and approaching on the other. They approach each other along one edge of the testicle, and terminate in a long narrow whitish body, as in a kind of axis.

From thence they divaricate in a regular manner, and are fixed by their opposite edges in the inner surface of the tunica albuginea, of which they appear to be a continuation. This white body may be termed the nucleus of the testicle.

From this description, we see that all these septa are not of an equal breadth; that the interstices between them are in some measure triangular; and that the extent of the small tubes, which lie therein, must be very considerable. They have been reckoned to amount to many cells, by taking the sum of all their several portions; and they may be easily unfolded by a long maceration, which destroys the delicate substance by which all their folds and convolutions are connected and tied down.

All these small canals seem to terminate by a smaller number of common trunks at the white body or nucleus already mentioned; which trunks do afterwards pierce the upper part of the anterior extremity of the testicle, and are disposed in several folds along the lateral external part of the upper edge, all the way to the posterior extremity. From this union arises a long whitish plaited fasciculus or bundle, called epididymis, or appendix to the testicle.

The epididymis thus formed, may be reckoned a production of the testicle, or a kind of testis accessorius; and

and it resembles in some measure an arch supported by its center or frame. It is more contracted at the middle, than at the extremities, by which it is closely united to those of the testicle.

Between its extremities it does not immediately touch the testicle, but is only loosely connected to it, by the duplicature of a very fine and almost transparent membrane, as by a kind of ligament. This membrane is the continuation and duplicature of the tunica albuginea or proper coat of the testicle, which having supplied the place of a ligament to the epididymis afterwards invests it.

The epididymis is flat, a little concave on the under side, or that next the testicle, irregularly convex on the upper side, or that turned from the testicle; and these two sides are distinguished by two angular edges; by the innermost of which, it is connected to the testicle, in the manner already said; but the outer edge and flat side are loose and free.

The anterior extremity or head of the epididymis arises from the testicle; and the posterior extremity or tail, which likewise adheres very closely to it, is incurvated from behind, forward, and a little upward, and contracting by degrees, forms a particular canal, termed vas deferens, which shall be described after the scrotum.

The scrotum is the cutaneous covering of the testes. Outwardly, it is a bag common to both, formed by a continuation of the skin of the neighbouring parts, and commonly very uneven, having a great number of rugæ on its outer surface. Interiorly it is fleshy, and forms a muscular capsula for each testicle, termed dartos.

The exterior or cutaneous portion of the scrotum is nearly of the same structure with the skin in general, of which it is a continuation; only it is something finer, and it is likewise plentifully studded with sebaceous glands and bulbs or roots of hairs.

Though it is a common covering for both testicles, it is nevertheless distinguished into two lateral parts by a superficial and uneven prominent line which appears like a kind of suture, and from thence has been termed raphe.

This line is a continuation of that which divides in the same manner the cutaneous covering of the penis; and it is continued through the perineum, which it divides likewise, all the way to the anus. It is only superficial, and does not appear on the inside of the skin.

The inner surface of this cutaneous bag is lined by a very thin cellular membrane, through which bulbs and glands appear very distinctly when we view its inside.

The dartos, or fleshy portion of the scrotum, is a true cutaneous muscle; the fibres of which are for the most part strongly connected to the skin, running through the cellular substance which lies between these two portions in place of a membrana adiposa, but without the least appearance of fat. This muscle is thin, and by the disposition of its fibres forms a bag with two cavities, or two small bags joined laterally to each other, and contained within the cutaneous portion.

The lateral parts of these two bags, which are turned from each other, are longer than those which are joined together; and by this union a septum is formed between the testes, which may be called mediastrum scroti.

The raphe or suture already mentioned adheres to the

edge of this septum, and thereby braces down the middle of the cutaneous portion, which from thence appears to have in part two cavities.

The aponeurotic or ligamentary expansion of the dartos is fixed in the ramus of the os pubis, between the musculus triceps and the origin of the corpus cavernosum of the same side, all the way to the lower part of the symphysis of these bones.

The vasa deferentia are two white solid flattened tubes, one lying on the right side, the other on the left. From the epididymis, of which they are continuations, each of them runs up in the cellular vagina of the spermatic vessels, as high as the openings in the abdominal muscles; the blood-vessels lying forward, and the vas deferens behind them.

This fasciculus, thus formed by the blood-vessels, vas deferens, and their common covering, is termed the spermatic rope. The covering is smoother on the outer than on the inner side, and for that reason it has been looked upon as a vagina; the internal substance of which is most cellular, and connects all the vessels together, while the external forms a covering to invest them.

The vas deferens having reached the membranous lamina of the peritoneum, where that lamina runs over the orifice of the vagina, separates from the blood vessels, and runs backward, in form of an arch, in the cellular substance of the peritoneum, as far as the nearest side of the bladder.

It passes afterwards behind the body of the bladder, to which it adheres very closely, as also to the lamina of the peritoneum which covers it, and then continues its arched course towards the neck of the bladder, where both vasa deferentia meet, and their arches terminate.

In this course, the vas deferens passes behind and crosses the neighbouring umbilical artery; crosses the extremity of the ureter of the same side, in its passage between that extremity and the bladder; and having got behind the bladder, it meets the vas deferens of the other side between the insertions of the ureters, and they run down together to the neck of the bladder.

This canal, which at the origin of the epididymis is pretty large and plaited, becomes immediately afterward smaller and smoother, and continues in that form till it gets behind the bladder, where it begins again to be larger and more uneven.

It arises from the angular portion or posterior extremity of the epididymis, and from thence runs forward in a very oblique course, on the posterior half of the epididymis, where it is a little incurvated as it joins the back-side of the spermatic vessels.

The cavity of the vas deferens is cylindrical, though the whole tube is flat, and its external circumference oval, and the cavity enlarges as it passes behind the bladder. The termination of these canals must be referred to the history of the urethra.

The particular coverings of the testes are commonly called coats; and they are reckoned to be three in number; the tunica musculosa, named cremaster, vaginalis, and albuginea. The first two are common to each testicle, and to the spermatic rope that belongs to it; and the third is peculiar to the testicle alone.

The tunica vaginalis is the most considerable of the three, and must be described first, in order to conceive the structure and connection of the cremaster, which is very improperly called a coat. The albuginea has been already described with the testes.

The tunica vaginalis is a continuation of the vagina of the spermatic rope, which, as it approaches the testicle, is gradually dilated, and forms two capsules, one contained within the other, the external being the longest and broadest at bottom; so that there is a void space there left between them, in which the testicle is lodged.

The inner surface of this coat is lined by a fine membrane, which strengthens the bottom of the vagina, and forms a kind of diaphragm, which prevents all communication between the vagina of the spermatic rope and the tunica vaginalis of the testicle.

The cremaster, improperly termed a coat, is a thin muscle or fleshy plane, which runs down round the vagina of the spermatic rope, and terminates in the tunica vaginalis of the testicle.

It surrounds almost the whole vagina, and afterwards expands itself on the upper and external part of the tunica vaginalis, in which it is inserted and lost.

It arises partly from the ligamentum Fallopii, and partly from the lower edge of the internal oblique muscle of the abdomen; and on this account it seems sometimes to arise from the spine of the os ilium.

The corpora cavernosa are two ligamentary and very slender tubes, united laterally to each side, through the greatest part of their length, and solid at their two extremities, two of which are connected together, and rounded like the end of a finger; the other two divaricate, like the branches of the greek Y, and diminishing gradually in size after the divarication, terminate in an oblique point. These divaricated and pointed extremities may be called the roots, and the round extremities the heads.

These two bodies are almost cylindrical, being round, and of an equal diameter from the roots to the heads, where they are in some measure conical. The ligamentary substance of their sides is elastic, and composed of fine close fibres, which are partly transverse, and partly more or less oblique.

The cavity of these ligamentary tubes is entirely filled by a strong cellular or cavernous substance, which does not seem to be a continuation of the substance of the sides. These cells communicate with each other, and are always more or less full of blood, resembling pretty much the cellular substance of the spleen; only with this difference, that the sides of the cells are thicker in these cavernous bodies, and without any additional substance.

By the union of the two corpora cavernosa, two external grooves are formed, one on the upper side, the other on the lower. The lower groove is something broader than the upper, and it is filled through its whole length by a third tube, narrower than the corpora cavernosa, called the urethra.

The roots of the corpora cavernosa are fixed, each, to the edge of the small ramus of the os ischium and os

pubis. They meet at the symphysis of the ossa pubis, where each of them becomes a cylindrical tube, and unites with the other in the manner already said.

The heads or rounded extremities join the basis of a distinct body, called the glans, which is an expansion of the urethra, and closely united to it.

By the union of the corpora cavernosa from their roots to their round extremities or heads, a particular septum is formed by the transverse fibres of both. Between the fibres of this septum several small void spaces are left, by which the corpora cavernosa communicate with each other.

The urethra is the third spongy tube which composes the penis, and it adheres to the corpora cavernosa through the whole length of the inferior groove formed by their union. It differs from the other two, both as it is narrower, and as it forms a true hollow canal. Its substance is spongy or cavernous, except a small portion next the bladder, and its inner and outer surfaces are membranous.

It is at first no more than a membranous canal continued from the anterior opening of the bladder, at the place called the neck of the bladder.

About a finger's breadth and an half from its origin, it joins a cavernous substance like that of the two other tubes, only smaller, which surrounds it through the whole extent of the inferior groove of the corpora cavernosa.

But before this spongy substance begins to surround the urethra, it forms a distinct oblong body, like a pear or onion, which is connected only to the lower convex side of the canal, and afterwards, being split on each side, invests it quite round. This body is called the bulb of the urethra, being larger than any other part of that canal, and divided interiorly by a very fine membranous septum, into lateral parts; and therefore when it is inflated, it appears to be double or with two heads.

The first portion of the urethra, or that which is not covered by the cavernous substance, and which from the bladder to the bulb is only a membranous canal, is sustained by a large solid whitish mass, of the figure of a chestnut, and situated between the bladder and the bulb of the urethra, its basis being toward the bladder, the apex or point toward the urethra, and the sides lying upward and downward.

This body is termed the prostates, from a greek word that expresses its situation before the vesiculae feminales, and implies a plurality, because it appears to be divided into two lateral lobes, by a hollow groove which runs through its upper side from the basis to the apex. The first portion of the urethra lies in this groove, adhering very closely to the prostates which surround it.

The body of the prostates lies on the intestinum rectum, and the apex is under the internal labium of the cartilaginous arch of the ossa pubis. The inner substance is spongy, but very compact; and in each lobe there are several folliculi which open into the first portion of the urethra, toward the bottom of the groove.

The spongy substance of the urethra, having reached the extremity of the corpora cavernosa, forms a large head, called the glans, which crowns the three spongy pillars,

pillars; with this difference however, that it is a continuation of the spongy substance of the urethra, and only adheres to the extremity of the corpora cavernosa without any direct communication.

The figure of the glans is that of a rounded cone, a little flattened at the lower part, and with an oblique prominent basis, the circumference of which is something greater than that of the corpora cavernosa.

The spongy substance of the glans is thick and uniform next the corpora cavernosa; but next the urethra, it is perforated by a continuation of that canal, and is there no thicker than the urethra before the formation of the glans.

Therefore the canal of the urethra does not lie in the middle of the glans, but continues its direct course thro' the lower flat side of it, all the way to the extremity, where it terminates by an oblong orifice.

All the convex surface of the glans is covered by a fine villous substance; and that again by a fine membrane, resembling the red part of the lips. The circumference of the basis of the glans has a double row of small papillæ, which may be reckoned sebaceous glands, from which a thick matter is discharged.

At the bottom of the cavity of the first portion of the urethra, or that which lies within the prostates, there is a small oblong oval eminence, pretty large on the back part, and terminating forward in a point, called caruncula or verumontanum. The large portion of it is commonly perforated by two holes, sometimes only by one, and very seldom by three; and these are the excretory orifices of the vesiculæ feminales. Each orifice has a small thin membranous border, which may serve for valves to the excretory ducts of the vesiculæ.

On each side of the large portion of the caruncula, there are five or six holes ranked in form of a crescent round its lateral parts; which are the orifices of the excretory ducts of the prostates that come from the folliculi already mentioned, and run in an oblique course to the orifices, in a kind of membranous duplicature.

The vesiculæ feminales are soft whitish knotty bodies, about three or four fingers breadth in length, one in breadth, and about three times as broad as thick, situated obliquely between the rectum and lower part of the bladder, in such a manner, as that their superior extremities are at a distance from each other, and their lower extremities united between those of the vasa deferentia, of which they imitate both the obliquity and the incurvation.

They are irregularly round on the upper part, and their breadth decreases gradually from thence. By the union of their lower extremities, they form a kind of fork, the branches of which are broad, and bent like rams horns. These extremities are very narrow, and form a small neck, which runs behind the bladder toward its orifice, and continues its course in the groove of the prostates, through the substance of the contiguous portion of the urethra, till its extremities pierce the caruncula in the manner already said.

The inner substance of the vesiculæ is plaited, and in a manner distinguished into several capsulæ, by contorted folds. Their external surface is covered by a fine

membrane, which serves for a border and frænum to the folds, and is a true continuation of the cellular substance of the peritoneum. The vesiculæ may easily be unfolded, and all their contortions straightened, and by this means they become much longer than in their natural state.

Their inner surface is villous and glandular, and continually furnishes a particular fluid, which exalts, refines, and perfects the semen, which they receive from the vasa deferentia, and of which they are the reservoirs for a certain time.

The passage of the vasa deferentia into the vesiculæ is very particular. It was observed, that these canals are incurvated behind the bladder, and that their contracted extremities unite at that place. They unite in an angle, and run between the contiguous extremities of the vesiculæ; and this union is so close, that the adhering portions seem to form only one middle septum, between two small tubes, each of which is formed, partly by the extremity of one vas deferens, and partly by that of the neighbouring vesicula.

This lateral union of the extremities of the vas deferens, and vesicula seminalis on each side, forms likewise a kind of short septum, which terminates in a crescent, like a small semilunar valve, and the extremity of the vas deferens is narrower than that of the vesicula. By this mechanism, the fluid contained in each vas deferens has liberty to enter the contiguous vesicula, but that contained in the vesicula cannot return into the other canal.

Afterwards the two small tubes, formed each by the extremities of the vas deferens and vesicula, run in between the basis of the prostates, and canal of the urethra; and perforating the sides of that canal obliquely, they terminate in the caruncula.

The inside of the canal of the urethra is lined by a fine membrane, full of capillary blood-vessels; and its surface is perforated by a great number of oblong holes or small lacunæ of different sizes, the largest lying near the glans.

These lacunæ, or orifices of the excretory ducts of the same number of small glands, are dispersed through the substance of the urethra. Which ducts run for some way in the spongy substance, along the convex side of the internal membrane of the urethra, and open obliquely from behind, forward into the great canal. The edges of the lacunæ are semilunar, or like a crescent.

A little way from the beginning of the cellular substance of the urethra, we meet with two lacunæ more considerable than the rest, and their ducts are very long. These lacunæ and ducts lead to two glandular bodies, situated on the two convex sides of the spongy substance of the urethra near the bulb. Each of them is about the size of a cherry-stone, but they are oblong and flat, and covered intirely by the muscles called acceleratores. These two bodies are commonly called prostate inferiores.

The cavity of the urethra resembles nearly that of a small writing pen. It is not every where round, and towards the gland becomes broader and flatter on one side, especially in the gland itself, where there is a kind of oval or navicular fossula.

This canal terminates at the extremity of the glans by

by a narrow oblong orifice or fissure, which is much less than the rest of the cavity. The commissures of this small fissure are turned one toward the convex, the other toward the flat side of the glans; and the labia of the fissure are its lateral parts; and it seems to be surrounded by fleshy fibres.

The præputium is a continuation of the skin of the pubis and scrotum, and it adheres all the way to the basis of the glans. The rest of the cutaneous integument covers the glans without adhesion, and terminates by an opening. This portion is named præputium, and along the whole lower or back side, both of the whole integument in general, and of the præputium in particular, there runs a fine suture, which is a continuation of the raphe of the perinæum and scrotum.

The inner surface of the præputium is lined with a fine membrane from the opening all the way behind the basis of the glans; and the same membrane is folded from behind, forward, round the glans, forming the proper integument thereof, and covering very closely its whole villous surface, as far as the orifice of the urethra, where it joins the membrane, which lines the inside of that canal.

This proper membrane of the glans, and internal membrane of the præputium, form conjointly along the flat part of the glans, from its basis to the orifice of the urethra, a membranous duplicature, which like a septum or mediastinum divides this part into two lateral portions, and limits the motions of the præputium; for which reason it is called frænum præputii.

The surface of the internal membrane of the præputium discharges a fluid which prevents it from adhering to the glans.

Several muscles are inserted in the parts which we have described in this paragraph.

The first two muscles are commonly termed erectores, or accelerators urinæ. The next two are called acceleratores. The four small muscles, two of which are superior, and two inferior, may be called prostatici.

The erectores lie along the roots of the corpora cavernosa; each of them being fixed by one extremity very obliquely, in the internal labium of the ramus of the os ischium, from the tuberosity upward. From thence it accompanies the root of the corpus cavernosum, all the way to the symphysis of the ossa pubis, and is fixed by its other extremity in the corpora cavernosa, near their union; where the fibres of both bodies meet, and are reciprocally expanded over both corpora. They lie a little lower, and more interiorly, than the roots of these cavernous bodies.

The musculi transversi, called also triangulares, are two long, narrow, fleshy fasciculi, inserted each by one extremity in the root or beginning of the ramus of the os ischium; from whence they run transversely along the edge of the interosseous ligament of the ossa pubis, as far as the apex of the prostates, where their other extremities meet, and form commonly a kind of digastric muscle, the middle of which gives insertion to the muscles of the urethra, and to the cutaneous sphincters of the anus.

The superior prostatici are two thin planes, fixed in the upper part of the inside of the small rami of the ossa pubis; from whence they are spread over and inserted in the prostates. Their insertions in the ossa pubis are on one side of those of the obturatores interni.

The prostatici inferiores are small transverse planes, each of which is fixed in the symphysis, between the ramus of the os pubis and os ischium, and from thence runs transversely, till it meets its fellow from the other side under the prostates, to which they are both strongly connected, and they serve like a girth to sustain these glands.

THE PARTS OF GENERATION IN FEMALES.

The parts of generation in females are several in number, some of them external, and some internal; and they are all subordinate to one principal internal part, called the uterus.

The uterus lies between the bladder and intestinum rectum. It is a body inwardly hollow, outwardly of a whitish colour, of a pretty solid substance, and, except in time of pregnancy, of the figure of a flat flask, being in adults about three fingers breadth in length, one in thickness, and two in breadth at one end, and scarcely one at the other.

The broadest portion is termed the fundus, and the narrowest the neck. Its situation is oblique, the fundus being turned backward and upward, and the neck forward and downward; the broad sides lie next the rectum and bladder, and the narrow sides are lateral.

The cavity of the uterus is flat, and resembles an oblong triangle, the shortest side of which answers exactly to the fundus, and the two longest sides lie one on the right-hand, the other on the left.

Of the three angles of this cavity, the two which terminate the fundus are perforated each by a narrow duct, which with difficulty admits a hog's bristle. The third angle forms a flat duct wider than the former, which perforates the neck of the uterus lengthwise, and terminates at the extremity of that neck by a transverse opening.

This opening is termed the internal orifice of the uterus; and, in the natural state, is narrower than the duct of the collum uteri, so that only a small stilet can be passed through it. At the edge of this orifice, are several small holes, answering to the same number of glandular corpuscles, which discharge a viscid lymph.

The inner surface of the cavity of the uterus is lined by a very fine membrane, which at the fundus or broad portion is smooth and even, but in the narrow portion which leads to the orifice it is wrinkled in a particular manner.

The portion of this membrane, which covers the bottom of the cavity, is perforated by a great number of considerable holes, through which small drops of blood may be observed to pass when the whole uterus is compressed.

In the narrow part, which answers to the collum, each side

side is divided into two lateral parts, by a kind of prominent longitudinal line, which is larger in the upper or anterior side, than in the lower or posterior.

On each side of these two longitudinal lines, there are lines or rugæ obliquely transverse, and disposed like branches, the longitudinal lines representing trunks. Between and round these rugæ, there are small lacunæ, through which a mucilaginous fluid is discharged that closes the orifice of the uterus.

The substance of the body of the uterus is spongy and compact, with a copious intertexture of vessels. Its thickness is nearly equal and uniform in the sides and edges, but the fundus is thicker toward the middle, than toward the two angles, where the thickness decreases gradually. The edges are likewise much thinner near these angles, than near the extremity of the neck.

The uterus is covered by a portion of the peritoneum, which serves it for a coat, and is the continuation of that which covers the bladder and intestinum rectum, running up from the lower and posterior part of the bladder, over the anterior part of the uterus, and from thence over the fundus, and down the backside, and afterwards going to the rectum.

On each lateral part or edge of the uterus, this portion of the peritoneum forms a broad duplicature, which is extended on each side, more or less directly to the neighbouring lateral parts of the pelvis, forming a kind of membranous septum between the anterior and posterior halves of the cavity of the pelvis; and it is afterwards continued in a loose manner with the peritoneum, on the sides of the pelvis.

These two broad duplicatures have the name of ligamenta lata, and vespertilionum alæ. The upper edge of each is partly double or folded, forming two small distinct duplicatures.

The laminae of all these duplicatures are connected by a cellular substance, in the same manner as the other duplicatures of the peritoneum; and they contain the Fallopian tubes, the ovaria, a part of the spermatic vessels, and of those that go to the body of the uterus, the ropes called the round ligaments, the nerves, &c.

The ovaria are two whitish, oval, flat, oblong bodies, situated on the sides of the fundus uteri; to which they are fixed by a kind of short round ligament, and inclosed, together with it, in the duplicature of the posterior pinion of the ligamenta lata.

They are composed of a compact spongy substance, and of several little balls, or transparent vesiculæ, which are called ova. The spongy substance surrounds each of these vesiculæ very closely, and seems likewise to furnish them with distinct spongy coverings or calices.

The ligaments of the ovaria lie in the edges of the posterior pinions of the ligamenta lata, much in the same manner as the umbilical vein in the anterior or umbilical ligament of the liver. They are round ropes of a filamentary texture, fixed by one extremity to the corner of the fundus uteri, a little above and behind the level of that fundus. They were formerly believed to be hollow, and looked upon as vasa deferentia.

The Fallopian tubes are two flaccid, conical and vermiform canals, situated more or less transversely on each

side of the uterus, between the fundus and the lateral parts of the pelvis, and included in the anterior duplicatures or pinions of the ligamenta lata.

Each of them is fixed by its narrow extremities in the corner of the fundus uteri, into which it opens, though by so narrow a duct, as hardly to admit a large bristle. From thence their diameter augments by degrees all the way to the other extremity, where it is about one third part of an inch. The body of the tubæ goes in a winding course, and their large extremity is bent toward the ovary.

These large extremities are irregularly round, and terminate by a narrow orifice, a little plaited, and turned toward the ovary, where it presently expands in form of a membranous fringe, full of plaits and incisures. These fringes are called the broad ends of the Fallopian tubes.

These tubes are composed of fleshy fibres, whereof some are longitudinal, and some obliquely circular, with an intertexture of another very fine substance.

The anterior pinions of the ligamentum latum serve for a common or external coat to both tubæ, and also to connect them, in the same manner as the mesentery connects the intestines. From thence the tubæ, and especially their fringes, come to be loose.

The pubes is that broad eminence at the lower part of the hypogastrium, between the two inguina, on which hairs grow at a certain age. This eminence is owing to a particular thickness of the membrana adiposa which cover the fore-part of the ossa pubis, and some small portions of the neighbouring muscles.

The longitudinal cavity which reaches from the middle and lower part of the pubes, within an inch of the anus, was by the ancients termed sinus; and they called the lateral parts of that cavity alæ, which is a more proper name than that of labia, commonly given to them. The places where the alæ are joined above and below are termed commissures; and may likewise be called the extremities or angles of the sinus.

The alæ are more prominent, and thicker above than below, and lie nearer each other below than above. They are chiefly composed of the skin, cellular substance, and fat. The exterior skin is a continuation of that of the pubes and inguina. It is more or less even, and furnished with a great number of glandular corpuscles, from which a whitish ceruminous matter may be expressed; and after a certain age it is likewise covered in the same manner with the pubes.

The inner side of the alæ is something like the red portion of the lips of the mouth; and it is distinguished every where from the external side by a kind of line, in the same manner as the red portion of the lips from the rest of the skin; being likewise thinner and smoother than the outward skin. A great number of pores are observable in it, and also numerous glandular corpuscles which furnish a liquor more or less sebaceous.

Near the inner edge of the inner surfaces of the alæ, on each side of the orifice of the canal of the uterus, we find a small hole more visible than the rest. These two holes are termed lacunæ; and they communicate by two small ducts with the same number of follicular bodies lying

ing in the substance of the alæ, and which may be looked upon as small prostates answering to the glandulæ prostaticæ in males. When compressed, they discharge a viscid liquor.

Above the superior commissure, a thin flat ligament runs down from each small branch of the ossa pubis, which penetrates the fat in the substance of each ala, and is lost therein insensibly near the edge. These may be looked upon as the ligamenta suspensoria of the alæ. The inferior commissure of the alæ is very thin, or like a membranous ligament, and, together with the neighbouring parts of the inner sides, it forms a fossula, termed navicularis or scaphoides. The space between the inferior commissure and anus, termed perinæum, is about a large finger's breadth in length.

The other external parts are situated in the sinus, and hid by the alæ. Directly under the superior commissure lies the clitoris, with its covering called præputium. A little lower is the orifice of the urethra; and below that is the orifice of the great canal of the uterus. The circumference of this orifice is bordered either by a membranous circle, called hymen, or by fleshy portions, termed carunculæ myrtiformes. On each side of the clitoris begins a very prominent fold like a crista, which runs down obliquely on each side of the orifice of the urethra. These folds are termed nymphæ, and they might likewise be named cristæ clitoridis.

The clitoris appears at first sight like a small imperforated glans. Its upper and lateral sides are covered by a kind of præputium, formed by a particular fold of a portion of the inner side of the alæ; which appears to be glandular, and to discharge a certain moisture, and its inside is granulated.

By dissection, we discover in the clitoris a trunk and two branches, as in the penis, made up of a spongy substance, and of very elastic coats, but without any urethra. The trunk is divided into two lateral parts of a middle septum, from the bifurcation, to the glans, where it is insensibly lost.

The bifurcation of the trunk is on the edge of the cartilaginous arch of the ossa pubis; and the branches which resemble the roots of the corpora cavernosa are inserted in the inferior rami of these bones, and in those of the ossa ischium, where they terminate by degrees; but there is sometimes a membranous tube on each side, which reaches to the tuberosity of the ischium.

The trunk of the clitoris is sustained by a ligamentum suspensorium fixed in the symphysis of the ossa pubis, and containing this trunk in its duplicature, nearly as in the other sex.

Four muscles or fasciculi of fleshy fibres are inserted in the trunk of the clitoris, two on each side. One of them runs down on the foreside of the neighbouring corpus cavernosum, and is inserted by a tendinous or aponeurotic portion, partly in the extremity of the corpus cavernosum, and partly in the tuberosity of the ischium. These two muscles are called erectores.

The other muscle on each side lies under the former, and runs down on the side of the urethra and great orifice of the uterus, all the way to the anus; increasing gra-

dually in breadth in its passage, and terminating partly like that which is called accelerator in males.

These two muscles surround very closely the lateral parts of the urethra, and of the great orifice. They expand very much as they descend, and are spread on the lower and lateral parts of the great orifice; for which reason several anatomists have looked upon them as muscular sphincters.

The nymphæ, cristæ clitoridis, or, as they may likewise be termed, alæ minores five internæ, are two prominent folds of the inner skin of the great or external alæ, reaching from the præputium of the clitoris to the two sides of the great orifice of the uterus. They begin very narrow, and, having increased in breadth in their course downward, they are again contracted at their lower extremity.

They are of a spongy substance, intermixed with glands, several of which may be perceived by the naked eye. Their situation is oblique, their upper extremities lying near each other, and the lower at a much greater distance. In married women they are more or less flaccid and decayed.

By the urethra in females, we mean the urinary duct, the orifice of which is between the nymphæ below the glans of the clitoris. The sides of this orifice are a little prominent and wrinkled, and perforated by small lacunæ, from which a viscid or mucilaginous liquor may be squeezed.

The body of the urethra is a spongy duct of the same structure as in males, but much shorter, situated directly under the trunk of the clitoris, and above the great canal of the uterus, adhering to each of these canals between which it lies, by membranous filaments. It passes under the cartilaginous arch of the ossa pubis, and terminates by an oblique opening at the neck of the bladder.

The great canal is situated below the urethra, and above the extremity of the intestinum rectum, a little obliquely, being more raised on the inner and back part, than on the outer and fore part.

Its inner or posterior extremity joins the extremity of the body of the uterus, and surrounds its orifice much in the same manner as the duodenum surrounds the pylorus, or as the ilium is surrounded by the cæcum and colon.

The anterior extremity forms the great orifice, which lies under that of the urethra, and above the fossula of the inferior commissure of the alæ.

The body of the canal is chiefly made up of a spongy substance, interwoven with numerous blood-vessels; and it is commonly longer and narrower in virgins, than in married women.

Its inner or concave surface, has several transverse rugæ, and is covered by a particular membrane. The rugæ are formed by oblong narrow eminences, incurved like portions of arches, placed very near each other, and disposed in such a manner as to divide the cavity of the canal into an upper and lower side.

By the union of the extremities of the upper and lower rugæ, a kind of raphe or suture is formed on the right and left sides; and both arches are sometimes intersected in the middle, and so form two half-arches.

In general, these arches are very considerable in young persons; become gradually more superficial in married women, and are quite lost in time of delivery.

The inner or posterior extremity of this great canal surrounds the orifice of the uterus, a little obliquely, in such a manner, as that the upper side of the canal lies very near the orifice, and the lower side at a greater distance from it, and this makes the extremity of the uterus appear to advance more into the canal on the lower than on the upper part.

The exterior or anterior extremity of the great canal in virgins, and especially before the first eruption of the menses, is commonly bordered by a circular membranous fold, of different breadths, more or less smooth, and sometimes semilunar, which in some subjects leaves but a very small opening, in others a large opening, and in all renders the external orifice narrower than the rest of the cavity. This fold, called hymen, is formed by the union of the internal membrane of the great canal with that on the inside of the ale, and represents a membranous circle of different breadths, and sometimes uneven.

This membranous circle is commonly ruptured after the consummation of marriage; is quite lost in delivery; and afterwards only some irregular portions of it remain, which, from their supposed resemblance to myrtle leaves, have been termed earuncule myrtiformes. This circle may likewise suffer some disorder by too great a flux of the menses, by imprudence, levity, and other particular accidents.

Each side of the anterior portion of the great canal is covered exteriorly by a thin broad cavernous and vascular plexus, called the plexus retiformis of that canal. These two planes run down on each side of the clitoris behind the nymphæ, and likewise cover the urethra like a collar, before they are spread on the great canal.

This plexus is strictly united to the muscular portions commonly taken for accelerators or constrictors, lying between these portions and the lateral parts of the urethra and of the great canal.

SECT. III. Of the Thorax.

By the thorax, we commonly understand all that part of the body which answers to the extent of the sternum, ribs, and vertæbræ of the back, both outwardly and inwardly.

The thorax is divided into the anterior part called commonly the breast, the posterior part called the back, and the lateral parts called the right and left sides.

The external parts of the thorax, besides the skin and membrana adiposa, are principally the mammae, and the muscles which cover the ribs and fill the spaces between them. In the mammae we see the papillæ or nipples, and a small coloured circle, which surrounds them.

The internal parts of the thorax are contained in the large cavity of that portion of the trunk, called the middle venter, or cavity of the breast. This cavity is lined by a membrane named pleura, and divided into two lateral cavities by a membranous septum named mediastinum, which is a production or duplicature of the pleura.

These parts are the heart, pericardium, trunk of the aorta, a portion of the aspera arteria and of the oesophagus, the ductus lacteus or thoracicus, the lungs, &c.

The hard parts, which form the sides of the cavity of the thorax, are the twelve vertæbræ of the back, all the ribs, and the sternum. The soft parts, which complete the sides, are the membrane called pleura, which lines the cavity, and the musculi inter-costales, sterno-costales, and diaphragma.

All these hard and soft parts taken together represent a kind of cage, in some measure of a conical figure, flattened on the foreside, depressed on the backside, and in a manner divided into two nooks by the figure of the vertæbræ of the back, and terminated below by a broad arched basis inclined backward. The intercostal muscles fill up the interstices betwixt the ribs, and so complete the sides of the cavity; the basis is the diaphragm, and the pleura not only covers the whole inner surface of the cavity, but, by forming the mediastinum, divides it into two, one on the right hand, the other on the left.

M A M M Æ.

The name of mammae, or breasts, is given to two eminences more or less round, situated in the anterior and a little toward the lateral parts of the thorax.

The body of the mammae is partly glandular, and partly made up of fat; or it is a glandular substance mixed with portions of the membrana adiposa, the cellular pelliculæ of which support a great many blood-vessels, lymphatics, and serous or lactiferous ducts, together with small glandular molleculæ which depend on the former; all of them being closely surrounded by two membranes continued from the pelliculæ.

The innermost of these two membranes, which is in a manner the basis of the body of the mamma, is thick and almost flat, adhering to the musculus pectoralis major. The second or external membrane is thinner, forming a particular integument for the body of the mamma, more or less convex, and adhering closely to the skin.

The corpus adiposum of the mamma in particular, is a spongy cluster, more or less interlarded with fat, or a collection of membranous pelliculæ, which, by the particular disposition of their outer sides, form a kind of membrane in shape of a bag, in which all the rest of the corpus adiposum is contained. The anterior or outer portion of this bag, or that which touches the skin, is very thin; but that side next the pectoralis major, is thick.

The glandular body contains a white mass, which is merely a collection of membranous ducts, narrow at their origin, broad in the middle, and which contract again as they approach the papilla, near which they form a kind of circle of communication. They are named ductus lactiferi.

The coloured circle or disk is formed by the skin, the inner surface of which sustains a great number of small glandular molleculæ. They appear very plainly all over the areola, even on the outside, where they form little flat heights or eminences at different distances quite round the circle.

The tubercle which lies in the center of the areola, is termed papilla, or the nipple. In women with child, or who give suck, it is pretty large, and generally longer or higher than it is thick or broad.

The texture of the nipple is spongy, elastic, and liable to divers changes of consistence, being sometimes harder, sometimes more flaccid. It seems to be made up chiefly of ligamentary fasciculi, the extremities of which form the basis and apex of the nipple.

Between these spongy and elastic fasciculi lie seven or eight particular tubes, at small distances from each other, and all in the same direction. These tubes end at the basis of the papilla in the irregular circle of communication of the lactiferous ducts, and at the apex, in the same number of almost imperceptible holes or orifices.

The use of the mammæ in the nourishment of children is known to all the world: But it is not certainly known what the papillæ and areolæ in males can be designed for. Milk has been observed in them, in children of both sexes.

PLEURA AND MEDIASTINUM.

THE pleura is a membrane which adheres very closely to the inner surface of the ribs, sternum, and musculi inter-costales, sub-costales, and sterno-costales, and to the convex side of the diaphragm. It is of a very firm texture, and plentifully studded with blood-vessels and nerves, in all which it resembles the peritoneum.

The cellular portion goes quite round the inner surface of the thorax, but the membranous portion is disposed in a different manner. Each side of the thorax has its particular pleura, intirely distinct from the other, and making as it were two great bladders, situated laterally with respect to each other in the great cavity of the breast, in such a manner as to form a double septum or partition running between the vertebræ and the sternum, their other sides adhering to the ribs and diaphragm.

This particular duplicature of the two pleuræ is termed mediastinum. The two laminæ of which it is made up are closely united together near the sternum and vertebræ; but in the middle, and toward the lower part of the fore-side, they are separated by the pericardium and heart. A little more backward they are parted in a tubular form by the œsophagus, to which they serve as a covering; and in the most posterior part, a triangular space is left between the vertebræ and the two pleuræ from above downward, which is filled chiefly by the aorta.

The mediastinum does not commonly terminate along the middle of the inside of the sternum, but inclines toward the left side.

The surface of the pleura turned to the cavities of the breast, is continually moistened by a lymphatic serosity which transudes through the pores of the membranous portion.

The pleura serves in general for an inner integument to the cavity of the thorax. The mediastinum cuts off all communication between the two cavities, and hinders one lung from pressing on the other when we lie on one side. It likewise forms receptacles for the heart, pericardium, œsophagus, &c.

THYMUS.

THE thymus is an oblong glandular body, round on the upper part, and divided below into two or three lobes, of which that toward the left hand is the longest. In the fœtus it is of a pretty large size, less in children, and very little in aged persons.

The greatest part of the thymus lies between the duplicature of the superior and anterior portion of the mediastinum, and the great vessels of the heart; from whence it reaches a little higher than the tops of the two pleuræ, so that some part of it is out of the cavity of the thorax.

Its particular inward structure and secretions are not as yet sufficiently known to determine its uses, which however seem to be designed more for the fœtus than for adults.

COR.

THE heart is a muscular body situated in the cavity of the thorax on the anterior part of the diaphragm, between the two laminæ of the mediastinum. It is in some measure of a conical figure, flattened on the sides, round at top, and oval at the basis. Accordingly, we consider in the heart the basis, apex, two edges, and two sides, one of which is generally flat, the other more convex.

Besides the muscular body, which chiefly forms what we call the heart, its basis is accompanied by two appendices called auriculæ, and by large blood-vessels; all these are included in a membranous capsula, named pericardium.

It is hollow within, and divided by a septum which runs between the edges into two cavities, called ventriculi, one of which is thick and solid, the other thin and soft. This latter is generally termed the right ventricle, the other the left ventricle, though in their natural situation the right ventricle is placed more anteriorly than the left.

Each ventricle opens at the basis by two orifices, one of which answers to the auricles, the other to the mouth of a large artery; and accordingly one of them may be termed the auricular orifice, the other the arterial orifice. The right ventricle opens into the right auricle, and into the trunk of the pulmonary artery; the left, into the left auricle, and into the great trunk of the aorta. At the edges of these orifices are found several moveable pelliculæ, called valves by anatomists; of which some are turned inward, toward the cavity of the ventricles, called triglochines or tricuspides; others are turned towards the great vessels, called semilunares or sigmoides. The valvulæ tricuspides of the left ventricle are likewise termed mitræ.

The inner surface of the ventricles is very uneven, many eminences and cavities being observable therein. The most considerable eminences are thick fleshy productions called columnæ. To the extremities of these pillars are fastened several tendinous cords, the other ends of which are joined to the valvulæ tricuspides. There are likewise other small short tendinous ropes along both edges of the septum between the ventricles. These small cords lie in an obliquely transverse situation, and form a kind of net-work at different distances.

The cavities of the inner surface of the ventricles are small deep fossulæ or lacunæ placed very near each other, with small prominent interstices between them.

The

The fleshy or muscular fibres of which the heart is made up, are disposed in a very singular manner, especially those of the right or anterior ventricle, being either bent into arches or folded into angles.

The fibres which are folded into angles are longer than those which are only bent into arches. The middle of these arches, and the angles of the folds, are turned towards the apex of the heart, and the extremities of the fibres towards the basis. These fibres differ not only in length, but in their directions, which are very oblique in all, but much more so in the long or folded fibres than in the short ones, which are simply bent.

Each ventricle is composed of its proper distinct fibres, but the left ventricle has many more than the right. Where the two ventricles are joined, they form a septum which belongs equally to both.

The fibres which compose the inner or concave surface of the ventricles, do not all reach to the basis; some of them running into the cavity, and there forming the fleshy columnæ, to which the loose floating portion of the tricuspidal valves is fastened by tendinous ropes.

The valves at the orifices of the ventricles are of two kinds. One kind allows the blood to enter the heart, and hinders it from going out the same way; the other kind allows the blood to go out of the heart, but hinders it from returning. The valves of the first kind terminate the auriculæ, and those of the second lie in the openings of the great arteries. The first are termed femular or sigmoidal valves, the others triglochines, tricuspidal, or mitral.

The tricuspidal valves of the right ventricle are fixed to its auricular orifice, and turned inward toward the cavity of the ventricle. They are three triangular productions, very smooth and polished on that side which is turned towards the auricle; and on the side next the cavity of the ventricle, they have several membranous and tendinous expansions, and their edges are notched or indented. The valves of the auricular orifice of the left ventricle are of the same shape and structure, but they are only two in number; and from some small resemblance to a mitre, they have been named mitrales.

The femular valves are six in number, three belonging to each ventricle, situated at the mouths of the great arteries; and they may be properly enough named valvæ arteriales.

The great artery that goes out from the left ventricle, is termed aorta. As it goes out, it turns a little toward the right hand, and then bends obliquely backward to form what is called aorta descendens.

The trunk of the artery which goes out from the right ventricle is called arteria pulmonaris. This trunk, as it is naturally situated in the thorax, runs first of all directly upward for a small space, then divides laterally into two principal branches, one for each lung; that which goes to the right lung being the longest, for a reason that shall be given hereafter.

The auricles are muscular bags situated at the basis of the heart, one towards the right ventricle, the other towards the left, and joined together by an inner septum, and external communicating fibres, much in the same manner with the ventricles; one of them being named the right auricle, the other the left. They are very uneven

on the inside, but smoother on the outside, and terminate in a narrow, flat, indented edge, representing a cock's comb, or in some measure the ear of a dog. They open into these orifices of each ventricle, which are named auricular orifices; and they are tendinous at their opening, in the same manner as the ventricles.

The right auricle is larger than the left, and it joins the right ventricle by a common tendinous opening. It has two other openings united into one, and formed by two large veins which meet and terminate there, almost in a direct line, called vena cava superior and inferior. The notched edge of this auricle terminates obliquely in a kind of obtuse point, which is a small particular production of the great bag, and is turned toward the middle of the basis of the heart.

The left auricle is a kind of muscular bag or reservoir, of a pretty considerable thickness, and unequally square, into which the four veins open, called venæ pulmonares, and which has a distinct appendix belonging to it, like a third small auricle. This bag is very even on both sides.

The heart lies almost transversely on the diaphragm, the greatest part of it being in the left cavity of the thorax, and the apex being turned toward the bony extremity of the sixth true rib. The basis is toward the right cavity; and both auricles, especially the right, rest on the diaphragm.

The origin or basis of the pulmonary artery is, in this natural situation, the highest part of the heart on the foreside; and the trunk of this artery lies in a perpendicular plane, which may be conceived to pass between the sternum and spina dorsi. Therefore some part of the basis of the heart is in the right cavity of the thorax; and the rest, all the way to the apex, is in the left cavity; and it is for this reason that the mediastinum is turned toward that side.

According to this true natural situation of the heart, the parts commonly said to be on the right side are rather anterior, and those on the left side posterior; and that side of the heart which is thought to be the foreside, is naturally the upper side, and the backside consequently the lower side.

The lower side is very flat, lying wholly on the diaphragm; but the upper side is a little convex through its whole length, in the direction of the septum between the ventricles.

The heart, with all the parts belonging to it, is contained in a membranous capsula, called pericardium, which is in some measure of a conical figure, and much bigger than the heart. It is not fixed to the basis of the heart, but round the large veins above the auricles, before they send off the ramifications, and round the large arteries, before their divisions.

The pericardium is made up of three laminæ, the middle and chief of which is composed of very fine tendinous filaments, closely interwoven and crossing each other in different directions. The internal lamina seems to be a continuation of the outer coat of the heart, auricles, and great vessels. The trunks of the aorta and pulmonary artery have one common coat which contains them both as in a sheath, and is lined on the inside by a cellular substance, chiefly in that space which lies between where.

where the trunks are turned to each other, and the sides of the sheath. There is but a very small portion of the vena cava contained in the pericardium.

The pericardium is closely connected to the diaphragm, not at the apex, but exactly at that place which answers to the flat or lower side of the heart; and it is a very difficult matter to separate it from the diaphragm in dissection.

The internal lamina is perforated by an infinite number of very small holes, through which a serous fluid continually transudes, in the same manner as in the peritoneum. This fluid being gradually collected after death, makes what is called aqua pericardii, which is found in considerable quantities in opening dead bodies while they remain fresh. Sometimes it is of a reddish colour, which may be owing to a transudation of blood through the fine membrane of the auricles.

The heart and parts belonging to it are the principal instruments of the circulation of the blood. The two ventricles ought to be considered as two syringes so closely joined together as to make but one body, and furnished with suckers placed in contrary directions to each other, so as that by drawing one of them, a fluid is let in, and forced out again by the other.

The heart is made up of a substance capable of contraction and dilatation. When the fleshy fibres of the ventricles are contracted, the two cavities are lessened in an equal and direct manner, not by any contortion or twisting, as the false resemblance of the fibres to a figure of eight has made anatomists imagine. For if we consider attentively in how many different directions, and in how many places, these fibres cross each other, as has been already observed, we must see clearly, that the whole structure tends to make an even, direct, and uniform contraction, more according to the breadth or thickness, than according to the length of the heart, because the number of fibres situated transversely, or almost transversely, is much greater than the number of longitudinal fibres.

The fleshy fibres thus contracted, do the office of suckers, by pressing upon the blood contained in the ventricles, which blood being thus forced toward the basis of the heart, presses the tricuspidal valves against each other, opens the semilunares, and rushes with impetuosity through the arteries and their ramifications, as through so many elastic tubes.

The blood thus pushed on by the contraction of the ventricles, and afterwards pressed by the elastic arteries, enters the capillary vessels, and is from thence forced to return by the veins to the auricles, which, like retirements, porches, or antichambers, receive and lodge the blood returned by the veins during the time of a new contraction. This contraction of the heart is by anatomists termed systole.

The contraction or systole of the ventricles ceases immediately, by the relaxation of their fleshy fibres; and in that time the auricles, which contain the venal blood, being contracted, force the blood through the tricuspidal valves into the ventricles, the sides of which are thereby dilated, and their cavities enlarged. This dilatation is termed diastole.

In this manner does the heart, by the alternate systole and diastole of its ventricles and auricles, push the blood through the arteries to all the parts of the body, and receive it again by the veins. This is called the circulation of the blood, which is carried on in three different manners.

The first and most universal kind of circulation is that by which almost all the arteries of the body are filled by the systole of the heart, and the greatest part of the veins evacuated by the diastole.

The second kind of circulation opposite to the first, is through the coronary vessels of the heart, the arteries of which are filled with blood during the diastole of the ventricles, and the veins emptied during the systole.

The third kind of circulation is that of the left ventricle of the heart; through the venal ducts of which a small quantity of blood passes, without going through the lungs, which is the course of all the remaining mass of blood.

PULMONES.

THE lungs are two large spongy bodies, of a reddish colour in children, greyish in adult subjects, and bluish in old age; filling the whole cavity of the thorax, one being seated in the right side, the other in the left, parted by the mediastinum and heart, and of a figure answering to that of the cavity which contains them; that is, convex next the ribs, concave next the diaphragm, and irregularly flattened and depressed next the mediastinum and heart.

They are distinguished into the right and left lung; and each of these into two or three portions called lobi, of which the right lung has commonly three, or two and a half, and the left lung two. The right lung is generally larger than the left, answerably to that cavity of the breast, and the obliquity of the mediastinum.

At the lower edge of the left lung, there is an indented notch or sinus opposite to the apex of the heart, which is therefore never covered by that lung, even in the strongest inspirations, and consequently the apex of the heart and pericardium may always strike against the ribs.

The substance of the lungs is almost all spongy, being made up of an infinite number of membranous cells, and of different sorts of vessels spread among the cells, in innumerable ramifications.

This whole mass is covered by a membrane continued from each pleura, which is commonly said to be double; but what is looked upon as the inner membrane is only an expansion and continuation of a cellular substance.

The vessels which compose part of the substance of the lungs are of three or four kinds; the air-vessels, blood-vessels, and lymphatics, and the nerves. The air-vessels make the chief part, and are termed bronchia.

These bronchia are conical tubes, composed of an infinite number of cartilaginous fragments, like so many irregular arches of circles, connected together by a ligamentary elastic membrane, and disposed in such a manner as that the lower easily insinuate themselves within those above them.

They

They are lined on the inside by a very fine membrane, which continually discharges a mucilaginous fluid; and in the substance of the membrane are a great number of small blood-vessels.

The bronchia are divided in all directions into an infinite number of ramifications, which diminish gradually in size; and as they become capillary, change their cartilaginous structure into that of a membrane.

Each of these numerous bronchial tubes is widened at the extremity, and thereby formed into a small membranous cell, commonly called a vesicle. These cells or folliculi are closely connected together in bundles; each small branch producing a bundle proportionable to its extent and the number of its ramifications.

These small vesicular or cellulous bundles are termed lobules; and as the great branches are divided into small rami, so the great lobules are divided into several small ones. The cells or vesicles of each lobule have a free communication with each other, but the several lobules do not communicate so readily.

The lobules appear distinctly to be parted by another cellulous substance, which surrounds each of them in proportion to their extent, and fills up the interstices between them. This substance forms likewise a kind of irregular membranous cells, which are thinner, looser, and broader than the bronchial vessels.

All the bronchial cells are surrounded by a very fine reticular texture of the small extremities of arteries and veins, which communicate every way with each other.

The blood-vessels of the lungs are of two kinds; one common, called the pulmonary artery and veins; the other proper, called the bronchial arteries and veins.

The pulmonary artery goes out from the right ventricle of the heart; and its trunk having run almost directly upward as high as the curvature of the aorta, is divided into two lateral branches, one going to the right-hand, called the right pulmonary artery, the other to the left, termed the left pulmonary artery. The right artery passes under the curvature of the aorta, and is consequently longer than the left. They both run to the lungs, and are dispersed through their whole substance by ramifications nearly like those of the bronchia, and lying in the same directions.

The pulmonary veins having been distributed through the lungs in the same manner, go out on each side, by two great branches, which open laterally into the reservoir or muscular bag of the right auricle.

Besides these capital blood-vessels, there are two others called the bronchial artery and vein.

Under the root of each lung, that is, under that part formed by the subordinate trunk of the pulmonary artery, by the trunks of the pulmonary veins, and by the trunk of the bronchia, there is a pretty broad membranous ligament, which ties the posterior edge of each lung to the lateral parts of the vertebrae of the back, from that root all the way to the diaphragm.

The bronchia already described are branches or ramifications of a large canal, partly cartilaginous, and partly membranous, called trachea, or aspera arteria. It is situated anteriorly in the lower part of the neck, from whence it runs down into the thorax betwixt the two

pleurae, through the upper space left between the duplication of the mediastinum, behind the thymus.

Having reached as low as the curvature of the aorta, it divides into two lateral parts, one toward the right-hand, the other toward the left, which enter the lungs, and are distributed through them in the manner already said. These two branches are called bronchia, and that on the right side is shorter than that of the left.

The trachea is made up of segments of circles or cartilaginous hoops, disposed in such a manner, as to form a canal open on the back part, the cartilages not going quite round; but this opening is filled by a soft glandular membrane, which completes the circumference of the canal.

Each circle is about the twelfth part of an inch in breadth, and about a quarter of that space in thickness. Their extremities are round; and they are situated horizontally above each other, small interstices being left between them, and the lower edge of the superior segments being turned toward the upper edge of those next below them.

They are all connected by a very strong elastic membranous ligament fixed to their edges.

The canal of the aspera arteria is lined on the inside by a particular membrane, which appears to be partly fleshy or muscular, and partly ligamentary, perforated by an infinite number of small holes, through which a mucilaginous fluid continually passes, to defend the inner surface of the trachea against the acrimony of the air.

This fluid comes from small glandular bodies dispersed through the substance of the membrane, but especially from the glands, something larger than the former, which lie on the outer or posterior surface of that strong membrane, by which the circumference of the canal is completed. The same structure is observable in the ramifications of the trachea from the greatest to the smallest.

At the angle of the first ramification of the trachea arteria, we find on both the fore and back sides, certain soft, roundish, glandular bodies, of a bluish or blackish colour, and of a texture partly like that of the thymus already described, and partly like that of the glandula thyroides. There are other glands of the same kind, as the origin of each ramification of the bronchia, but they decrease proportionably in number and size. They are fixed immediately to the bronchia, and covered by the interlobular substance; and they seem to communicate by small openings with the cavity of the bronchia.

Respiration is performed by organs of two kinds, one of which may be looked upon as active, the other as passive. The lungs are of the second kind, and the first comprehends chiefly the diaphragm and intercostal muscles.

As soon as the intercostal muscles begin to contract, the arches of the ribs are raised together with the sternum, and placed at a greater distance from each other; by which means the cavity of the thorax is enlarged on the two lateral and anterior sides.

At the same instant the diaphragm is flattened or brought toward a plane by two motions, which are apparently contrary; that is, by the contraction of the diaphragm, and the dilatation of the ribs in which it is inserted. The external surface of the thorax being thus in a manner increased, and the cavity of the bronchia

being at the same time, and by the same means, less resisted or pressed upon; the ambient air yields to the external pressure, and insinuates itself into all the places where the pressure is diminished, that is, into the aspera arteria, and into all the ramifications of the bronchia all the way to the vesicles. This is what is called inspiration.

This motion of inspiration is instantaneous, and ceases in a moment by the relaxation of the intercostal muscles; the elastic ligaments and cartilages of the ribs bringing them back at the same time to their former situation. This motion, by which the ribs are depressed and brought nearer each other, is termed expiration.

The pulmonary arteries and veins which accompany the bronchia through all their ramifications, and surround the vesicles, transmit the blood through their narrow capillary extremities, and thereby change or modify it, at least in three different manners.

The first change or modification which the blood undergoes in the lungs, is to have the cohesions of its parts broken, to be attenuated, pounded, and, as it were, reduced to powder. The second is, to be deprived of a certain quantity of serum, which transpires through the lungs, and is what we commonly call the breath. The third is to be in a manner reanimated by the impression of the air.

OESOPHAGUS.

The oesophagus is a canal partly muscular, and partly membranous, situated behind the trachea arteria, and before the vertebrae of the back, from near the middle of the neck, down to the lower part of the thorax; from whence it passes into the abdomen through a particular hole of the small or inferior muscle of the diaphragm, and ends at the upper orifice of the stomach.

It is made up of several coats, almost in the same manner as the stomach, of which it is the continuation. The first coat, while in the thorax, is formed only by the duplicature of the posterior part of the mediastinum, and

is wanting above the thorax and the neck, where the outer coat of the oesophagus is only a continuation of the cellular substance belonging to the neighbouring parts.

The second coat is muscular, being made up of several strata of fleshy fibres.

The third is termed the nervous coat, and is like that of the stomach and intestines.

The fourth or innermost coat resembles in some measure that of the intestines, except that instead of the villi it has small and very short papillæ. Through the pores of this coat, a viscid lymph is continually discharged.

The oesophagus from its very beginning, turns a little to the left hand, and naturally runs along the left extremities of the cartilages of the aspera arteria. The thyroid gland, pharynx and larynx, shall be described in another place.

DUCTUS THORACICUS.

The thoracic duct is a thin transparent canal, which runs up from the receptaculum chyli, along the spina dorsi, between the vena azygos and aorta, as high as the fifth vertebra of the back, or higher. From thence it passes behind the aorta toward the left hand, and ascends behind the left subclavian vein, where it terminates in some subjects by a kind of vesicula, in others by several branches united together, and opens into the back-side of the subclavian vein near the outside of the internal jugular.

This canal is plentifully furnished with semilunar valves turned upward. Its opening into the subclavian vein in the human body, is, in the place of valves, covered by several pelliculæ, so disposed as to permit the entrance of the chyle into the vein, and hinder the blood from running into the duct. It is sometimes double, one lying on each side, and sometimes it is accompanied by appendices called pampiniformes.

EXPLANATION OF PLATE XIX.

FIGURE 1. shews the contents of the thorax and abdomen, in situ.

1, Top of the trachea, or wind-pipe. 2 2, The internal jugular veins. 3 3, The subclavian veins. 4, The vena cava descendens. 5, The right auricle of the heart. 6, The right ventricle. 7, Part of the left ventricle. 8, The aorta ascendens. 9, The pulmonary artery. 10, The right lung, part of which is cut off to shew the great blood-vessels. 11, The left lung entire. 12 12, The anterior edge of the diaphragm. 13 13, The two great lobes of the liver. 14, The ligamentum rotundum. 15, The gall bladder. 16, The stomach. 17 17, The jejunum and ilium. 18, The spleen.

FIG. 2. Shews the organs subservient to the chylopoetic viscera, —with those of urine and generation.

1 1, The under side of the two great lobes of the liver. 2, Lobulus Spigelii. 3, The ligamentum rotundum.

3, The gall-bladder. 4, The pancreas. 5, The spleen. 6 6, The kidneys. 7, The aorta descendens. 8, Vena cava ascendens. 9 9, The renal veins covering the arteries. 10, A probe under the spermatic vessels and a bit of the inferior mesenteric artery, and over the ureters. 11 11, The ureters. 12 12, The iliac arteries and veins. 13, The rectum intestinum. 14, The bladder of urine.

FIG. 3. Shews the chylopoetic viscera, and organs subservient to them, taken out of the body intire.

A A, The under side of the two great lobes of the liver. B, Ligamentum rotundum. C, The gall-bladder. D, Ductus cysticus. E, Ductus hepaticus. F, Ductus communis choledochus. G, Vena portarum. H, Arteria hepatica. I I, The stomach. K K, Venæ & arteriæ gastro-epiploicæ, dextræ & sinistræ. L L, Venæ & arteriæ coronariæ ventriculi. M, The spleen. N N, Mesocolon, with its vessels. O O O, Intestinum

testinum colon. P, One of the ligaments of the colon, which is a bundle of longitudinal muscular fibres. Q Q Q Q, Jejunum and ilium. R R, Sigmoid flexure of the colon with the ligament continued, and over. S, The rectum intestinum. T T, Levatores ani. U, Sphincter ani. V, The place to which the prostate gland is connected. W, The anus.

FIG. 4. Shews the heart of a fœtus at the full time, with the right auricle cut open to shew the foramen ovale, or passage between both auricles.

a, The right ventricle. b, The left ventricle. c c, The outer side of the right auricle stretched out. d d, The posterior side, which forms the anterior side of the septum. e, The foramen ovale, with the membrane or valve which covers the left side. f, Vena cava inferior passing through g, A portion of the diaphragm.

FIG. 5. Shews the heart and large vessels of a fœtus at the full time.

a, The left ventricle. b, The right ventricle. c, A part of the right auricle. d, Left auricle. e e, The right branch of the pulmonary artery. f, Arteria pulmonalis. g g, The left branch of the pulmonary artery, with a number of its largest branches dissected from the lungs. h, The canalis arteriosus. i, The arch of the aorta. k k, The aorta descendens. l, The left subclavian artery. m, The left carotid artery. n, The right carotid artery. o, The right subclavian artery. p, The origin of the right carotid and right subclavian arteries in one common trunk. q, The vena cava superior or descendens. r, The right common subclavian vein. s, The left common subclavian vein.

N. B. All the parts described in this figure are to be found in the adult, except the canalis arteriosus.

EXPLANATION OF PLATE XX.

FIG. 1. Represents the under and posterior side of the bladder of urine, &c.

a, The bladder. b b, The insertion of the ureters. c c, The vasa deferentia, which convey the semen from the testicles to d d, The vesiculæ seminales,—and pass through e, The prostate gland, to discharge themselves into f, The beginning of the urethra.

FIG. 2. A transverse section of the penis.
g g, Corpora cavernosa penis. h, Corpus cavernosum urethræ. i, Urethra. k, Septum penis. ll, The septum between the corpus cavernosum urethræ, and that of the penis.

FIG. 3. A longitudinal section of the penis.
m m, The corpora cavernosa penis, divided by o, The septum penis. n, The corpus cavernosum glandis, which is the continuation of that of the urethra.

FIG. 4. Represents the female organs of generation.
a, That side of the uterus which is next the os sacrum. 1, Its fundus. 2, Its cervix. b b, The Fallopian or uterine tubes, which opens into the cavity of the uterus;—but the other end is open within the pelvis, and surrounded by c c, The fimbriæ. d d, The ovaria. e, The os internum uteri, or mouth of the womb. f f, The ligamenta rotunda, which passes without the belly, and is fixed to the labia pudendi. g g, The

cut edges of the ligamenta lata, which connects the uterus to the pelvis. h, The infide of the vagina. i, The orifice of the urethra. k, The clitoris surrounded by (l) the præputium. m m, The labia pudendi. n n, The nymphæ.

FIG. 5. Shews the spermatic ducts of the testicle filled with mercury.

A, The vas deferens. B, Its beginning, which forms the posterior part of the epididymis. C, The middle of the epididymis, composed of serpentine ducts. D, The head or anterior part of the epididymis unravelled. e e e e, The whole ducts which compose the head of the epididymis unravelled. f f, The vasa efferentia. g g, Rete testis. h h, Some reticular ducts which send off the vasa efferentia. i i, The substance of the testicle.

FIG. 6. The right testicle intire, and the epididymis filled with mercury.

A, The beginning of the vas deferens. B, The vas deferens ascending towards the abdomen. C, The posterior part of the epididymis, named globus minor. D, The spermatic vessels inclosed in cellular substance. E, The body of the epididymis. F, Its head, named globus major. G, Its beginning from the testicle. H, The body of the testicle, inclosed in the tunica albuginea.

SECT. IV. Of the BRAIN and its Appendages.

THE name of brain is given to all that mass which fills the cavity of the cranium, and which is immediately surrounded by two membranes called meninges or matres.

This general mass is divided into three particular portions; the cerebrum or brain properly so called, the cerebellum, and medulla oblongata. To these three parts a fourth is added, which fills the great canal of the spinal cord, by the name of medulla spinalis, being a continuation of the medulla oblongata.

The

The meninges or membranes are two in number. The first is named dura mater; the second pia mater, which is again divided into two; the external lamina being termed arachnoides, the internal retaining the common name of pia mater.

DURA MATER.

The dura mater incloses the brain and all its appendages. It lines the inside of the cranium, and supplies the place of an internal periosteum, being spread in all the holes and depressions, and covering all the eminences in such a manner as to prevent their being hurtful to the brain.

The dura mater is made up of two laminae, adhering very closely together; the fibres of both crossing each other obliquely. Their texture is very close and strong, appearing to be partly ligamentary and partly tendinous.

The dura mater sticks closely to the cranium by a great number of filaments of the external lamina, which enter the pores of the bones chiefly at the sutures both above and below; and by penetrating these joints, they communicate with the external periosteum.

These adhesions are formed intirely by the external lamina. The internal lamina is very smooth and polished on the inside, which is also continually moistened by a fine fluid discharged through its pores, much in the same manner as in the peritoneum and pleura.

The folds of the dura mater are made by the internal lamina; and three of them form particular septa; one of which is superior, representing a kind of mediastinum between the two great lobes of the brain. The second is in a middle situation, like a diaphragm between the cerebrum and cerebellum; the third is inferior, between the lobes of the cerebellum. The superior septum is longitudinal, in form of a fessure, from whence it is termed the falx of the dura mater. The middle septum is transverse, and might be called the diaphragm of the brain. The inferior septum is very small, and runs down between the lobes of the cerebellum.

Besides these large folds, there are two small lateral ones on each side of the fossa turcica, each running from the posterior to the anterior clynoid apophysis on the same side. These two folds, together with the anterior and posterior parts of the fossa turcica, form a small fossula in which the pituitary gland is lodged.

The elongations of the dura mater are productions of both laminae, which go beyond the general circumference, and pass out of the cranium.

The most considerable of these elongations passes through the great occipital foramen, and runs down the common canal of the vertebrae in form of a tube, lining the inside of that canal, and inclosing the medulla spinalis, by the name of the dura mater of that medulla. The other elongations accompany the nerves out of the cranium in form of vagine, which are more numerous than the nervous trunks reckoned in pairs.

There are two particular elongations which form the peritoneum of the orbits, together with the vagine of the optic nerves. These orbital elongations go out by the sphenoidal or superior orbital fissures, and, increa-

sing in breadth in their passage, line the whole cavity of the orbits, at the edges of which they communicate with the pericranium and periosteum of the face.

The elongations of the dura mater which accompany the blood-vessels through the foramina of the cranium, unite with the pericranium immediately afterwards. Such, for instance, are the elongations which line the fossulae of the foramina lacera or jugularia, and the bony or carotid canals of the apophysis petrosa, &c.

The dura mater contains in its duplicature several particular canals, into which the venal blood not only of that membrane, but of the whole brain, is carried. These canals are termed sinuses, and some of them are disposed in pairs, others in uneven numbers; that is, some of them are placed alone, in a middle situation; others are disposed laterally on each side of the brain. The most ancient anatomists reckoned only four; to which we can now add four times as many.

These sinuses are in the duplicature of the dura mater; and their cavities are lined on the inside by particular very fine membranes. They may be enumerated in this manner.

The great sinus of the falx, or superior longitudinal sinus, which was reckoned the first by the ancients.

Two great lateral sinuses, the second and third of the ancients.

The sinus called torcular Herophili, the fourth of the ancients.

The small sinus of the falx, or inferior longitudinal sinus.

The posterior occipital sinus, which is sometimes double.

Two inferior occipital sinuses, which form a portion of a circle, and may likewise be called the inferior lateral sinuses.

Six sinus petrosi, three on each side, one anterior, one middle or angular, and one inferior. The two inferior, together with the occipital sinuses, complete a circular sinus round the great foramen of the os occipitis.

The inferior transverse sinus.

The superior transverse sinus.

The two circular sinuses of the fossa sphenoidalis; one superior, and one inferior.

Two sinus cavernosi, one on each side.

Two orbital sinuses, one on each side.

All these sinuses communicate with each other, and with the great lateral sinuses by which they discharge themselves into the internal jugular veins, which are only continuations of these lateral sinuses. They likewise unload themselves partly into the vertebral veins, which communicate with the small lateral or inferior occipital sinuses; and partly into the external jugular veins, by the orbital sinuses which communicate with the venae angulares, frontales, nasales, maxillares, &c. as the lateral sinuses likewise communicate with the venae occipitales, &c.

Thus the blood which is carried to the dura mater, &c. by the external and internal carotid, and by the vertebral arteries, is returned to the heart by the external and internal jugular and vertebral veins; so that when the passage of the blood is obstructed in any particular place, it finds another way, by virtue of these communications, though not with the same ease.

Fig. 1.

This engraving shows a longitudinal section of a uterus. The central cavity is labeled 'a'. Two fallopian tubes, labeled 'c', extend from the upper corners of the uterus. At the distal ends of these tubes are the ovaries, labeled 'd'. The outer muscular wall of the uterus is labeled 'b'. The cervix, the lower neck of the uterus, is labeled 'f'.

Fig. 4.

This engraving shows the female reproductive system from a posterior perspective. The uterus is labeled 'h'. The fallopian tubes are labeled 'f'. The ovaries are labeled 'd'. The external genitalia at the top are labeled 'b'. The internal pelvic structures at the bottom are labeled 'n', 'k', 'l', and 'm'.

Fig. 2.

This engraving shows a cross-section of a fallopian tube. The central lumen is labeled 'h'. The outer wall is labeled 'g'. The fimbriated end of the tube is labeled 'l'.

Fig. 5.

This engraving shows a longitudinal section of a fallopian tube. The internal lumen is labeled 'h'. The outer wall is labeled 'g'. The fimbriated end is labeled 'l'. Other labels include 'A' at the distal end, 'B' at the proximal end, 'C' at the base, and 'D' at the fimbriae.

Fig. 3.

This engraving shows a longitudinal section of a fallopian tube. The internal lumen is labeled 'h'. The outer wall is labeled 'g'. The fimbriated end is labeled 'l'. Other labels include 'A' at the distal end and 'm' within the wall.

Fig. 6.

This engraving shows a longitudinal section of a fallopian tube. The internal lumen is labeled 'h'. The outer wall is labeled 'g'. The fimbriated end is labeled 'l'. Other labels include 'A' at the distal end, 'B' at the proximal end, 'C' at the base, 'D' at the fimbriae, and 'E' at the fimbriated end.

THIS membrane surrounds the whole mass of the brain more particularly than the dura mater. It adheres very closely to the brain, and is connected to the dura mater only by the veins which open into the sinuses.

The pia mater is made up of two very fine laminae, the outermost of which covers pretty uniformly all the convex surface of the brain, and lines in the same manner all the concave or inner surface of the dura mater. The internal lamina forms a great number of plicæ, duplicatures, and septa, which insinuate themselves into all the folds and circumvolutions, and between the different strata of the cerebrum and cerebellum.

THE cerebrum properly so called, is a kind of medullary mass, of a moderate consistence, and of a greyish colour on the outer surface, filling all the superior portion of the cavity of the cranium, or that portion which lies above the transverse septum. The upper part of the cerebrum is of an oval figure, like half an egg cut lengthwise. It is flattened on the lower part, each lateral half of which is divided into three eminences, called lobes, one anterior, one middle, and one posterior.

The substance of the cerebrum is of two kinds, distinguished by two different colours; one part of it, which is softest, being of a greyish or ash colour; the other, which is more solid, being very white. The ash-coloured substance lies chiefly on the outer part of the cerebrum like a kind of cortex, from whence it has been named substantia corticalis or cinerea. The white substance occupies the inner part, and is named substantia medullaris, or simply substantia alba.

The cerebrum is divided into two lateral portions, separated by the falx, or great longitudinal septum of the dura mater. They are generally termed hemispheres. Each of these portions is divided into two extremities, one anterior and one posterior, which are termed the lobes of the cerebrum, between which there is a large inferior protuberance which goes by the same name; so that in each hemisphere there are three lobes, one anterior, one middle, and one posterior.

The anterior lie upon these parts of the os frontis which contribute to the formation of the orbits and of the frontal sinuses, commonly called the anterior fossæ of the basis cranii. The posterior lobes lie on the transverse septum; and the middle lobes, in the middle or lateral fossæ of the basis cranii.

Each lateral portion of the cerebrum has three sides; one superior, which is convex; one inferior, which is uneven; and one lateral, which is flat, and turned to the falx. Through the whole surface of these three sides we see inequalities or windings like the circumvolutions of intestines, formed by waving streaks or furrows very deep and narrow, into which the septa or duplicatures of the pia mater insinuate themselves, and thereby separate these circumvolutions from each other.

Near the surface these circumvolutions are at some di-

stance from each other, representing serpentine ridges; and in the interstices between them, the superficial veins of the cerebrum are lodged, between the two laminae of the pia mater, from whence they pass in the duplicature of the dura mater, and so open into the sinuses.

These circumvolutions are fixed through their whole depth to the septa or duplicatures of the pia mater, by an infinite number of very fine vascular filaments.

When they are cut transversely, we observe that the substantia alba lies in the middle of each circumvolution, so that there is the same number of internal medullary circumvolutions as of external cortical ones.

Having cut off the falx from the crista galli, and turned it backward; if we separate gently the two lateral parts or hemispheres of the cerebrum, we see a longitudinal portion of a white convex body, which is named corpus callosum. It is a middle portion of the medullary substance, which under the inferior sinus of the falx, and also a little toward each side, is parted from the mass of the cerebrum, to which it is simply contiguous from one end of that sinus to the other.

The surface of the corpus callosum is covered by the pia mater, which runs in between the lateral portions of this body, and the lower edge of each hemisphere.

The corpus callosum becomes afterwards continuous on each side with the medullary substance, which through all the remaining parts of its extent is intirely united with the cortical substance, and together with the corpus callosum forms a medullary arch or vault of an oblong or oval figure. After which we will observe a medullary convexity much smaller than that which is common to the whole cerebrum, but of the same form; so that it appears like a medullary nucleus of the cerebrum.

Under this arch are two lateral cavities, much longer than they are broad, and very shallow, separated by a transparent medullary septum. These cavities are named the anterior, superior, or great lateral ventricles of the cerebrum.

The lateral ventricles are broad, and rounded at these extremities which lie next the transparent septum. They go from before backward, contracting in breadth, and separating from each other gradually in their progress. Afterwards they bend downward, and return obliquely from behind forward, in a course like the turning of a ram's horn, and terminate almost under their superior extremities. These ventricles are lined with a thin membrane.

The transparent partition or septum lucidum, lies directly under the raphe or suture of the corpus callosum, of which it is a continuation. It is made up of two medullary laminae, more or less separated from each other by a narrow medullary cavity, sometimes filled with a serous substance.

The septum lucidum is united by its lower part, to the anterior portion of that medullary body, called the fornix with three pillars.

The fornix being cut off and inverted, or quite removed, we see first of all a vascular web, called plexus choroides, and several eminences more or less covered by the expansion of that plexus. There are four pairs of

eminences which follow each other very regularly, two large, and two small. The first two great eminences are named corpora striata; and the second, thalami nervorum opticorum. The four small eminences are closely united together; the anterior being called nates, and the posterior testes. Immediately before these tubercles there is a single eminence, called glandula pinealis.

The corpora striata got that name, because in scraping them with the knife we meet with a great number of white and ash-coloured lines alternately disposed, which are only the transverse section of the medullary and cortical laminae, mixed together in a vertical position in the basis of the cerebrum.

They lie in the bottom of the superior cavity of the lateral ventricles, which they resemble in some measure in shape, their anterior parts being near the septum lucidum, from which they separate gradually as they run backward, and diminish in size.

The thalami nervorum opticorum are so named, because these nerves arise chiefly from them. They are two large eminences placed by the side of each other, between the posterior portions or extremities of the corpora striata. Their figure is semi-spheroidal and a little oval; and they are of a whitish colour on the surface; but their inner substance is partly greyish and partly white.

These two eminences are closely joined together, and at their convex part they are so far united as really to become one body, the whitish outer substance being continued uniformly over them both.

Immediately within this whitish common substance these two eminences are closely contiguous till about the middle of their thickness; and from thence they separate insensibly toward the bottom, where by the space left between them a particular canal is formed, named the third ventricle, one extremity of which opens forward, the other backward.

At the bottom these two eminences are elongated downward toward both sides, into two thick, round, whitish cords, which separate from each other like horns, by a large curvature; and afterwards by a small curvature turned forward in an opposite direction to the former, and representing the tip of an horn, they approach each other again. The size of these ropes diminishes gradually from their origin to their anterior reunion.

The tubercles are four in number, two anterior, and two posterior; adhering together as if they made but one body, situated behind the union of the thalami nervorum opticorum. Their surface is white, and their inner substance greyish, and are called nates and testes.

Directly under the place where the tubercles of one side are united to those of the other side, lies a small middle canal, which communicates by its anterior opening with the third ventricle, under the thalami nervorum opticorum, and by its posterior opening with the fourth ventricle, which belongs to the cerebellum.

Where the convex parts of the two anterior tubercles join these posterior convex parts of the thalami nervorum opticorum, an interstice or opening is left between these four convexities which communicates with the third ventricle, and with the small middle canal. Instead of the

ridiculous name of anus, which has been given to this opening, it may be called foramen commune posterius.

The glandula pinealis is a small soft greyish body, about the size of an ordinary pea, irregularly round, and sometimes of the figure of a pine apple, situated behind the thalami nervorum opticorum, above the tubercula quadrigemina. It is fixed like a small button to the lower part of the thalami by two very white medullary pedunculi, which at the gland are very near each other, but separate almost transversely toward the thalami.

It seems to be mostly of a cortical substance, except near the footstalks, where it is something medullary.

Between the basis of the anterior pillar of the fornix, and the anterior part of the union of the optic thalami, lies a cavity or fossula named infundibulum. It runs down towards the basis of the cerebrum, contracting gradually, and terminates in a straight course, by a small membranous canal, in a softish body situated in the sella turcica, named glandula pituitaria. The infundibulum opens above, immediately before the optic thalami, by an oval hole named foramen commune anterius, and consequently communicates with the lateral ventricles.

At the lower part of the thalami nervorum opticorum, directly under their union, lies a particular canal, called the third ventricle of the cerebrum.

This canal opens forward into the infundibulum under the foramen commune anterius, by which it likewise communicates with the lateral ventricles. It opens backward under the foramen commune posterius, between the thalami and tubercula quadrigemina, opposite to the small middle canal which goes to the cerebellum.

The plexus choroides is a very fine vascular texture, consisting of a great number of arterial and venal ramifications, partly collected in two loose fasciculi, which lie one in each lateral ventricle, and partly expanded over the neighbouring parts, and covering in a particular manner the thalami nervorum opticorum, glandula pinealis, tubercula quadrigemina, and the other adjacent parts both of the cerebrum and cerebellum, to all which it adheres.

The pituitary gland is a small spongy body lodged in the sella turcica between the sphenoidal folds of the dura mater. It is of a singular kind of substance, which seems to be neither medullary nor glandular. On the outside it is partly greyish and partly reddish, and white within. It is transversely oval or oblong, and on the lower part in some subjects it is divided by a small notch into two lobes, like a kidney-bean. It is covered by the pia mater as by a bag, the opening of which is the extremity of the infundibulum, and it is surrounded by the small circular sinuses which communicate with the sinus cavernosi.

CEREBELLUM.

The cerebellum is contained under the transverse septum of the dura mater. It is broader laterally than on the fore or back sides, flattened on the upper side, and gently inclined both ways, answerable to the septum, which serves it as a kind of tent or ceiling. On the lower side it is rounder; and on the backside it is divided into

into two lobes, separated by the occipital septum of the dura mater.

It is made up, like the cerebrum, of two substances, but it has no circumvolutions on its surface. Its sulci are pretty deep, and disposed in such a manner as to form thin flat strata, more or less horizontal, between which the internal lamina of the pia mater insinuates itself by a number of septa equal to that of the strata.

Under the transverse septum, it is covered by a vascular texture, which communicates with the plexus choroïdes. It has two middle eminences called appendices vermisiformes; one anterior and superior, which is turned forward; the other posterior and inferior, which goes backward. There are likewise two lateral appendices, both turned outward.

Besides the division of the cerebellum into lateral portions or into two lobes, each of these lobes seems to be likewise subdivided into three protuberances, one anterior, one middle or lateral, and one posterior.

When we separate the two lateral portions or lobes, having first made a pretty deep incision, we discover first of all the posterior portion of the medulla oblongata; and in the posterior surface of this portion, from the tubercula quadrigemina, all the way to the posterior notch in the body of the cerebellum, and a little below that notch, we observe an oblong cavity which terminates backward like the point of a writing pen. This cavity is what is called the fourth ventricle.

At the beginning of this cavity, immediately behind the small common canal which lies under the tubercles, we meet with a thin medullary lamina, which is looked upon as a valve between that canal and the fourth ventricle. A little behind this lamina, the cavity grows wider towards both hands, and then contracts again to its first size. It is lined interiorly by a thin membrane, and seems oftentimes to be distinguished into two lateral parts, by a kind of small groove, from the valvular lamina to the point of the calamus scriptorius.

This membrane is a continuation of that which lines the small canal, the third ventricle, infundibulum, and the two great ventricles.

On each side of this ventricle the medullary substance forms a trunk which expands itself in form of laminae through the cortical strata. When one lobe of the cerebellum is cut vertically from above downward, the medullary substance will appear to be dispersed in ramifications through the cortical substance. These ramifications have been named arbor vite; and the two trunks from whence these different laminae arise, are called pedunculi cerebelli.

MEDULLA OBLONGATA.

THE medulla oblongata is a medullary substance situated from before backward in the middle part of the bases of the cerebrum and cerebellum without any discontinuation, between the lateral parts of both these bases; and therefore it may be looked upon as one middle medullary basis common to both cerebrum and cerebellum, by the reciprocal continuity of their medullary substances, through the great notch in the transverse septum of the

dura mater; which common basis lies immediately on that portion of the dura mater which lines the basis of the cranium. The medulla oblongata is therefore justly esteemed to be a third general part of the whole mass of the brain, or as the common production or united elongation of the whole medullary substance of the cerebrum and cerebellum.

It is extremely difficult, if not altogether impossible, to examine or demonstrate it as we ought, in its natural situation; but we are obliged to do both on a brain inverted.

The lower side of the medulla oblongata in an inverted situation, presents to our view several parts which are in general either medullary productions, trunks of nerves, or trunks of blood vessels.

The chief medullary productions are these: The large or anterior branches of the medulla oblongata; which have likewise been named crura anteriora, femora, and brachia medullæ oblongatæ, and pedunculi cerebri: The transverse protuberance, called likewise processus annularis, or pons varolii: The small or posterior branches, called pedunculi cerebelli, or crura posteriora medullæ oblongatæ: The extremity or cauda of the medulla oblongata, with two pairs of tubercles, one of which is named corpora olivaria, the other corpora pyramidalia; and to all these productions we must add a production of the infundibulum and two medullary papillæ.

The great branches of the medulla oblongata are two very considerable medullary fasciculi, the anterior extremities of which are separated, and the posterior united, so that, taken both together, they represent a Roman V.

The transverse, annular, or rather semi-annular protuberance, is a medullary production, which seems at first sight to surround the posterior extremities of the great branches; but the medullary substance of this protuberance is in reality intimately mixed with that of the two former. Varolius, an ancient Italian author, viewing those parts in an inverted situation, compared the two branches to two rivers, and the protuberance to a bridge over them both, and from thence it has the name of pons Varolii.

The small branches of the medulla oblongata are lateral productions of the transverse protuberance, which by their roots seem to encompass that medullary portion in which the fourth ventricle or calamus scriptorius is formed.

The extremity is no more than the medulla oblongata contracted in its passage backward to the anterior edge of the great foramen of the os occipitis, where it terminates in the medulla spinalis; and in this part of it several things are to be taken notice of. We see first of all, four eminences, two named corpora olivaria, and the other two corpora pyramidalia. Immediately afterwards, it is divided into two lateral portions by two narrow grooves, one on the upper side, the other on the lower. They both run into the substance of the medulla, as between two cylinders, flattened on that side by which they are joined together.

When we separate these ridges with the fingers, we observe a crucial intertexture of several small medullary cords,

cords, which go obliquely from the substance of one lateral portion into the substance of the other.

The corpora olivaria and pyramidalia are whitish eminences situated longitudinally near each other on the lower side of the extremity or cauda, immediately behind the transverse or annular protuberances. The corpora olivaria are in the middle, so that the interstice between them, which is a kind of superficial groove, answers to the inferior groove of the following portion.

The corpora pyramidalia are two lateral eminences depending on the olivaria. These four eminences are situated on the lower half of the medulla.

The tubercula mammillaria, or papillæ medullares, which are situated very near the production of the infundibulum, have been taken for glands.

These tubercles seem to have some immediate relation to the roots or bases of the anterior pillar of the fornix.

The beak or tube of the infundibulum is a very thin production from the sides of that cavity; and it is strengthened by a particular coat given to it by the pia mater. It is bent a little from behind forward, toward the glandula pinealis, and afterwards expands again round this gland.

The membrana arachnoides, or external lamina of the pia mater, appears to be very distinctly separated from the internal lamina, in the interstices between all these eminences on the lower side of the medulla oblongata, without any visible cellular substance between them.

From this medulla oblongata, arise almost all the nerves which go out of the cranium through the different foramina by which its basis is perforated. It likewise produces the medulla spinalis, which is no more than a common elongation of the cerebrum and cerebellum, and of their different substances; and therefore the medulla oblongata may justly be said to be the first origin or primitive source of all the nerves of the human body.

MEDULLA SPINALIS.

THE medulla spinalis is only an elongation of the extremity of the medulla oblongata; and it has its name from its being contained in the bony canal of the spina dorsi; consequently a continuation or common appendix of the cerebrum or cerebellum, as well because of the two substances of which it is composed, as because of the membranes by which it is invested.

The dura mater, after it has lined the whole internal surface of the cranium, goes out by the great occipital foramen, and forms a kind of funnel, in its progress downward through the bony canal of the vertebrae.

The spinal marrow is made up of a cortical and medullary substance, as the cerebrum and cerebellum; but with this difference, that the ash-coloured substance lies within the other; and in a transverse section of this medulla, the inner substance appears to be of the figure of an horse-shoe.

The body of the medulla spinalis runs down all the way to the first vertebra of the loins, where it terminates in a point. The size of it is proportionable to that of

the bony canal, so that it is larger in the vertebrae of the neck than those of the back.

It sends off from both the fore and back sides, at different distances, flat fasciculi of nervous filaments. The anterior and posterior fasciculi having got a little beyond the edge of the medulla, unite in pairs, and form on each side a kind of knots, called ganglions by anatomists, each of which produces a nervous trunk. These ganglions are made up of a mixture of cortical and medullary substance, accompanied by a great number of small blood-vessels.

The dura mater, which invests the medulla, sends out on each side the same number of vaginæ as there are ganglions and nervous trunks. These vaginæ are productions of the external lamina; the internal lamina, which is very smooth and polished on the inside, being perforated by two small holes very near each other, where each vagina goes off, through which holes the extremities of each anterior and posterior fasciculus are transmitted; and immediately after their passage through the internal lamina, they unite.

USES OF THE BRAIN AND ITS APPENDAGES IN GENERAL.

MALPIGHI was the first who discovered the brain to be a gland, or an organ fitted to separate some particular fluid from the mass of blood.

The infinite number of small secretory clusters strain or filter the mass of blood carried to them by the numerous ramifications, and separate from it an excessively fine fluid; the remaining blood being conveyed back by the same number of venal extremities, into the sinuses of the dura mater, and from thence into the jugular and vertebral veins.

This subtle fluid, commonly called animal spirit, nervous juice, or liquor of the nerves, is continually forced into the medullary fibres of the white portion of the cerebrum, cerebellum, medulla oblongata, and medulla spinalis; and by the intervention of these fibres supplies and fills the nerves, which are a continuation of them.

PERICRANIUM.

BESIDES the external integuments of the head, the skin, hair, and cellular substance, there is an aponeurotic expansion which covers the head like a cap, and is spread round the neck and on the shoulders like a riding-hood.

This aponeurosis is very strong on the head, and it appears to be made up at least of two strata of fibres crossing each other. As it is spread on the neck it becomes gradually thinner, and ends insensibly on the clavicles. It sends out a production on each side, from above downward, and from without inward, which having passed over the superior extremity of the musculus sterno-mastoideus, runs behind that muscle toward the transverse apophyses of the vertebrae of the neck, where it communicates with the ligamenta inter-transversalia.

The external surface of all the bones of the head, as well

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well as of all the other bones of the human body, except the teeth, is covered by a particular membrane, of which that portion which particularly invests the cranium is named pericranium, and that which invests the bones of the face is simply termed periosteum.