forcibly throwing certain liquid medicines into the body by means of a syringe, tube, clyster-pipe, or the like.

surgery, the throwing in some liquor or medicine into a vein opened by incision. This practice, and that of transfusion, or the conveying the arterial blood of one man, or other animal, into another, were once greatly practised, but are now laid aside.

Anatomical Injection, the filling the vessels of a human, or other animal body, with some coloured substance, in order to make their figures and ramifications visible.

I. The best account of the method of injecting the sanguiferous vessels of animals, is that by the late Dr Monro, published in the Medical Essays, vol. i. p. 79.

"The instrument with which the liquor is commonly thrown into the vessels is a tight easy going syringe of brass, to which several short pipes are fitted, and can be fixed by screws, the other extremities of these pipes being of different diameters without any screw, that they may slide into other pipes, which are so exactly adapted to them at one end, that when they are pressed a little together, nothing can pass between them: and because their cohesion is not so great as to resist the pushing force of the injection, which would drive off this second pipe, and spoil the whole operation; therefore the extremity of this second sort of pipes, which receives the first kind, is formed on the outside into a square, bounded behind and before by a rising circle, which hinders the key that closely grasps the square part from sliding backwards or forwards; or a bar of brass must stand out from each side of it to be held with the fingers. The other extremity of each of these second sort of pipes is of different diameter; and near it a circular notch, capable of allowing a thread to be sunk into it, is formed; by this, the thread tying the vessel at which the injection is to be made, will not be allowed to slide off.

Besides this form described, common to all this second sort of pipes, we ought to have some of the larger ones, with an additional mechanism, for particular purposes; as, for instance, when the larger vessels are injected, the pipe fastened into the vessel ought either to have a valve or a stop-cock, that may be turned at pleasure, to hinder anything to get out from the vessel by the pipe; otherwise, as the injection, in such a case, takes time to coagulate, the people employed in making the injection must either continue all that while in the same posture; or, if the syringe is too soon taken off, the injected liquor runs out, and the larger vessels are emptied. When the syringe is not large enough to hold at once all the liquor necessary to fill the vessels, there is a necessity of filling it again. If, in order to do this, the syringe was to be taken off from the pipe fixed in the vessel, some of the injection would be lost, and what was exposed to the air would cool and harden; therefore some of the pipes ought to have a reflected curve tube coming out of their side, with a valve so disposed, that no liquor can come from the straight pipe into the crooked one, but, on the contrary, may be allowed to pass from the crooked to the straight one: the injector then, taking care to keep the extremity of the reflected pipe immersed in the liquor to be injected, may, as soon as he has pushed out the first syringeful, fill it again by only drawing back the sucker; and, repeating this quickly, will be able to throw several syringefuls into the vessels.

All these different sorts of pipes are commonly made of brass.

The liquors thrown into the vessels, with a design to fill the small capillary tubes, are either such as will incorporate with water, or such as are oily; both kinds have their advantages and inconveniences; which I shall mention in treating of each, and shall conclude with that which I have found by experience to succeed best.

All the different kinds of glue, or ichthyocolla, syths, common glue, &c. dissolved and pretty much diluted, mix easily with the animal-fluids, which is of great advantage, and will pass into very small vessels of a well-chosen and prepared subject, and often answer the intention sufficiently, where the design is only to prepare some very fine membrane, on which no vessels can be expected to be seen so large as the eye can discover whether the transverse sections of the vessels would be circular, or if their sides are collapsed. But when the larger vessels are also to be prepared, there is a manifest disadvantage to the usefulness and beauty of the preparation; for if nothing but the glutinous liquor is injected, one cannot keep a subject so long as the glue takes of becoming firm; and therefore, in dissecting the injected part, several vessels will probably be cut and emptied. To prevent this, one may indeed either soak the part well in alcohol, which coagulates the glue; but then it becomes so brittle, that the least handling makes it crack; and if the preparation is to be kept, the larger vessels appear quite shrivelled, when the watery part of the injection is evaporated: or the efflux of the injection may be prevented, by carefully tying every vessel before we are obliged to cut it; still, however, that does not hinder the vessels to contract when the glue is drying. If, to obviate these difficulties, the glutinous liquor should first be injected in such quantity as the capillary vessels will contain, and the common oily or waxy injection is pushed in afterwards to keep the larger vessels distended, the wax is very apt to harden before it has run far enough; the two sorts of liquors never mix to mix irregularly, and the whole appears interrupted and broken by their soon separating from each other; which is still more remarkable afterwards, when the watery particles are evaporated.

Spirits of wine coloured mixes with water and oils, and so far is proper to fill the very smaller vessels with; but, on the other hand, it coagulates any of our liquor it meets, which sometimes blocks up the vessels so much, that no more injection will pass; then Injection. it scarce will suspend some of the powders that prove the most durable colours; and as it entirely evaporates, the vessels must become very small; and the small quantity of powder left, having nothing to serve for connecting its particles together, generally is seen so interrupted, that the small ramifications of vessels rather have the appearances of random scratches of a pencil, than of regular continued canals.

"Melted tallow, with a little mixture of oil of turpentine, may sometimes be made to fill very small vessels, and keeps the larger ones at a full stretch; but where any quantity of the animal liquors are still in the vessels, it is liable to stop too soon, and never can be introduced into numbers of vessels which other liquors enter; and it is so brittle, that very little handling makes it crack, and thereby renders the preparation very ugly (a).

"The method I have always succeeded best with, in making what may be called subtile or fine injections, is, first to throw in coloured oil of turpentine, in such a quantity as might fill the very small vessels; and, immediately after, to push the common coarse injection into the larger ones. The oil is subtile enough to enter rather smaller capillary tubes than any colouring can; its resinous parts, which remain after the spirituous are evaporated, give a sufficient adhesion to the particles of the sublimate with which it is coloured, to keep them from separating; and it intimately incorporates with the coarser injection; by which, if the injection is rightly managed, it is impossible for the sharpest eye to discover that two sorts have been made use of (b).

"All the liquors with which the vessels of animals are artificially filled, having very faint, and near the same colours, would not all appear in the very small vessels, because of their becoming entirely diaphanous, without a mixture of some substance to impart its colour to them; and where several sorts of even the largest vessels of any part were filled, one sort could not be distinguished from another, unless the colour of each was different; which has likewise a good effect in making preparations more beautiful. Wherefore anatomists have made use of a variety of such substances, according to their different fancies or intentions; such as gamboge, saffron, ink, burnt ivory, &c., which can be easily procured from painters. My design being only to consider those that are fit to be mixed with the injecting liquors proposed to fill capillary vessels, which is scarce ever to be done in any other, except the branches of the arteries and of some veins, I shall confine myself to the common colours employed to these last named two sorts of vessels, which colours are red, green, and sometimes blue, without mentioning the others, which require very little choice.

"Anatomists have, I imagine, proposed to imitate the natural colours of the arteries and veins in a living creature, by filling the arteries with a red substance, and the veins with a blue or green: from which, however, there are other advantages, such as the strong reflection which such bodies make of the rays of light, and the unaptness most such bodies have to transmit these same rays, without at least a considerable reflection of the rays peculiar to themselves; or, in other words, their unfitness to become completely pellucid; without which, the very fine vessels, after being injected, would still be imperceptible. The animal or vegetable substances made use of for colouring injections, such as cochineal, lacquer, rad. acus, brazillwood, indigo, &c., have all one general fault of being liable to run into little knots which stop some of the vessels; their colour fades sooner when kept dry; they more easily yield their tincture when the parts are preserved in a liquor; and rats, mice, and insects, will take them for food; for which reasons, though I have frequently succeeded in injecting them, I rather prefer the mineral kind, such as minium or vermilion for red; of which this last is, in my opinion, the best, because it gives the brightest colour, and is commonly to be bought finely levigated. The green-coloured powder generally used is verdigrase; but I rather choose that preparation of it called distilled verdigrase; because its colour is brighter, and it does not so often run into small knots as the common verdigrase, but dissolves in the oily liquors.

"The method of preparing the injection composed of these materials, is to take for the fine one, a pound of clear oil of turpentine, which is gradually poured on three ounces of vermilion, or distilled verdigrase finely powdered, or rather well levigated by grinding on marble; stir them well with a small wooden spatula till they are exactly mixed, then strain all thro' a fine linen rag. The separation of the groser particles is, however, rather better made, by pouring some ounces of the oil upon the powder, and, after stirring them together strongly, stop rubbing with the spatula for a second or so, and pour off into a clean vessel the oil with the vermilion or verdigrase suspended in it; and continue this sort of operation till you observe no more of the powder come off; and all that remains is granulated. The coarser injection is thus prepared: Take tallow, 1 pound; wax, bleached white, 5 ounces; fallad oil, 3 ounces; melt them in a skillet put over a lamp; then add Venice turpentine, 2 ounces; and as soon as this is dissolved, gradually sprinkle in of vermilion or verdigrase prepared, 3 ounces; then pass all through a clean, dry, warmed linen-cloth, to separate all the groser particles; and, when you design to make it run far into the vessels, some oil of

---

(a) Rigierus (Introductio, in notitiam rerum naturae, &c. 4to, Hagae, 1743, titul. Balamum) gives Ruysh's method of injecting and preserving animals, which, he says, Mr Blumentrost, president of the Peterburgh academy, assured him was copied from the receipt given in Ruysh's own hand-writing to the Czar. According to this receipt, melted tallow, coloured with vermilion, to which, in the summer, a little white wax was added, was Ruysh's injecting ceracia materies.

(b) Mr Ranby's injecting matter, as published by Dr Hales, (Hemast. Ex. 21.), is white rosin and tallow, of each two ounces, melted and strained through linen; to which was added three ounces of vermilion, or finely ground indigo, which was first well rubbed with eight ounces of turpentine varnish. Injection of turpentine may be added immediately before it is used.

"The next thing to be considered, and indeed what chiefly contributes to the success of injections, is the choice and preparation of the subject whose vessels are to be filled.

"In choosing a fit subject, take these few general rules: 1. The younger the creature to be injected is, the injection will, ceteris paribus, go farther, and vice versa. 2. The more the creature's fluids have been dissolved and exhausted in life, the success of the operation will be greater. 3. The less solid the part designed to be injected is, the more vessels will be filled. 4. The more membranous and transparent parts are, the injection shows better; whereas, in the solid very hard parts of a rigid old creature, that has died with its vessels full of thick strong blood, it is scarce possible to inject great numbers of small vessels.

"Therefore, in preparing a subject for injecting, the principal things to be aimed at, are, To dissolve the fluids, empty the vessels of them, relax the solids, and prevent the injection's coagulating too soon. To answer all these intentions, authors have proposed to inject tepid or warm water by the arteries, till it returns clear and untincted by the veins, and the vessels are thereby so emptied of blood, that all the parts appear white; after which, they push out the water by forcing in air; and, lastly, by pressing with their hands, they squeeze the air also out. After this preparation, one can indeed inject very subtilly; but generally there are inconveniences attend it. For in all the parts where there is a remarkable tunica cellulosa, it never misses to be full of the water, which is apt to spoil any parts designed to be preserved either wet or dry; and some particles of the water seldom mix to be mixed in the larger as well as smaller vessels with the oily injection, and make it appear discontinued and broken: wherefore it is much better to let this injection of water alone, if it can be possibly avoided, and rather to macerate the body or part to be injected a considerable time in water, made to warm (c) as one can hold his hand easily in it; taking care to keep it of an equal warmth all the time, by taking out some of the water as it cools, and pouring in hot water in its place; by which the vessels will be sufficiently softened and relaxed, the blood will be melted down, and the injection can be in no danger of hardening too soon; whereas, if the water is too hot, the vessels shrink, and the blood coagulates. From time to time we squeeze out the liquids as much as possible at the cut vessel by which the injection is to be thrown in (v). The time this maceration is to be continued, is always in proportion to the age of the subject, the bulk and thickness of what we design to inject, and the quantity of blood we observe in the vessels, which can only be learned by experience; at least, however, care ought to be taken, that the whole subject, or part macerated, is perfectly well warmed all through; and that we continue the pressure with our hands till no more blood can be brought away, whatever position we put the subject in.

"When the syringe, injections, and subject, are all in readiness, one of the second sort of pipes is chosen, as near to the diameter of the vessel by which the injection is to be thrown as possible; for if the pipe is too large, it is almost needless to tell it cannot be introduced. If the pipe is much smaller than the vessel, it is scarce possible to tie them so firmly together, but, by the wrinkling of the coats of the vessel, some small passage will be left, by which part of the injection will spring back on the injector in the time of the operation, and the nearest vessels remain afterwards undisturbed, by the loss of the quantity that oozes out. Having chosen a fit pipe, it is introduced at the cut orifice of the vessel, or at an incision made in the side of it; and then a waxed thread being brought round the vessel, as near to its coats as possible, by the help of a needle, or a flexible eyed probe, the surgeon's knot is made with the thread, and it is drawn as firmly as the thread can allow; taking care that it shall be sunk into the circular notch of the pipe all round, otherwise it will very easily slide off, and the pipe will be brought out probably in the time of the operation, which ruins it.

"If there have been large vessels cut, which communicate with the vessels you design to inject, or if there are any others proceeding from the same trunk, which you do not resolve to fill, let them be all carefully now tied up, to save the injected liquor, and make the operation succeed better in the view you then have.

"When all this is done, both sorts of injections are to be warmed over a lamp, taking care to stir them constantly, lest the colouring powder fall to the bottom and burn (e). The oil of turpentine needs be made no warmer than will allow the finger to remain in it, if the subject has been previously well warmed in water; when the maceration has not been made, the oil ought to be scalding hot, that it may warm all the parts which are designed to be injected. The coarse injection ought to be brought near to a boiling. In the mean time, having wrapped several folds of linen round the parts of the syringe, which the operator is to grip, and secured the linen with thread, the syringe is to be made very hot by sucking boiling water several times up (r), and the pipe within the vessel is to be warmed by applying a sponge dipped in boiling water to it (g).

"After all is ready, the syringe being cleared of the water, the injector fills it with the finer injection; and

(c) Ruyfch orders a previous maceration for a day or two in cold water; which must have a better effect in melting the blood than warm water has.

(d) When Ruyfch intended to inject the whole body, he put one pipe upwards, and another downwards, in the descending aorta.

(e) Ruyfch melts his tallow by the heat of warm water, into which he puts the vessel containing the injection.

(f) He warms his syringe by laying it on hot coals.

(g) He warms his pipe, by putting the body, after the pipe is fixed in the vessel, into hot water. When this and then introducing the pipe of the syringe into that in the vessel, he presses them together, and either with one hand holds this last pipe firm, with the other gripes the syringe, and with his breast pushes the sucker; or, giving the pipe in the vessel to be held by an assistant, in any of the ways mentioned in the description of these sorts of pipes, he gripes the syringe with one hand, and pushes the sucker with the other, and consequently throws in the injection, which ought to be done slowly, and with no great force, but proportioned to the length and bulk of the part to be injected and strength of the vessels. The quantity of this fine injection to be thrown in is much to be learned by use. The only rule I could ever fix to myself in this matter was to continue pushing till I was sensible of a stop which would require a considerable force to overcome. But this will not hold where all the branches of any vessel are not injected; as for instance, when the vessels of the thorax only are to be injected: for the aorta bears too great a proportion to the branches sent from it, and therefore less fine injection is requisite here. As soon as that stop is felt, the sucker of the syringe is to be drawn back, that the nearest large vessels may be emptied. Then the syringe is taken off, emptied of the fine injection, and filled with the coarser, which is to be pushed into the vessels quickly and forcibly, having always regard to the strength and firmness of the vessels, bulk, &c. of the part. Continue to thrust the sucker, till a full stop, or a sort of push backwards, is felt, when you must beware of thrusting any more, otherwise some of the vessels will be bursted, and the whole, or a considerable share of the preparation you designed, will be spoiled by the extravasation, but rather immediately stop the pipe by the turn-cock, and take out the syringe to clean it, and allow sufficient time for the coarse injection to coagulate fully, before any part is dissected. Ruysh, immediately after throwing in the injection, put the body into cold water, and stirred it continually for some time, to prevent the vermilion to separate from the tallow."

II. The injection of the lymphatic system is much more difficult than that of the sanguiferous, on account of the extreme smallness of the vessels; so that till very lately it was almost quite impracticable. Methods indeed had been attempted for this purpose; but by reason of the improper form of the instruments, and the inferior skill of anatomists in former times, we may justly look upon this as one of the most modern improvements in anatomy.

The first thing to be considered, when the lymphatics are to be injected, is a proper method of discovering them; for this is by no means an easy matter, on account of their smallness and transparency.—To find out these vessels, the subject must be viewed in a proper place, where the light is neither very strong nor very weak. Mr Sheldon, who has written a treatise upon this subject, recommends a winter forenoon from ten to two; it being chiefly in the winter season that anatomical preparations are made, and because at that time of the day the light is more clear and steady. He says also from his own experience, that the light passing through the glass of a window is better for this purpose than the open air, as the vessels are more distinctly seen. The injecting of the vessels is likewise rendered more difficult in the open air by the ease with which the humidity is evaporated from them. It will likewise be necessary to incline the part in various ways to the light, as some of the vessels are most easily discoverable in one position and some in another. The lacteal trunks under the peritoneal coats of the intestines, and the lymphatics on the external surface of the liver, &c. particularly require this method. He disapproves the use of magnifying glasses. "I am persuaded (says he), that those who attempt to find them through this medium, will not acquire that visus eruditus which is obtained to a surprising degree by those who have been much experienced in injecting lymphatic vessels. A lateral light is likewise preferable to an horizontal, or even to an oblique sky-light.

The subjects must be laid upon a table of sufficient height, which might be contrived with a ledge fixed to the table in such a manner as to be water proof; which would be useful for preventing the quicksilver, which is almost always necessary for injecting these vessels, from being lost. The surface of the table should likewise be hollowed, so that the mercury which falls may be collected in the middle, where an hole with a stopper may be made to take out occasionally the quicksilver which collects. Such a table would also be convenient for holding water for the purpose of steeping membranous parts which are frequently to be injected; and which, from being exposed to the air, become dry; which also it is inconvenient and hazardous to move into water during the time of operation. Even a common table with a hole cut in the middle may answer the purpose: the hole may be round or square according to the fancy of the anatomist; but the table must be constructed of such materials as are not liable to warp in warm water. Should the anatomist not be provided with either of these tables, the parts must be laid in a tray or earthen dish, that the quicksilver may be saved."

The materials for injecting these vessels are only quicksilver, and the ceraceous or coarse injection of anatomists; the former being always used in injecting the lymphatics and lacteals, it being almost impossible to fill them with another fluid in the dead body. The ceraceous injection is chiefly used for the thoracic duct; and in some particular instances, where the lymphatic trunks have been found larger than the ordinary size, a coarse injection has been made use of.

Injections of the lymphatics may be made even while the animal is alive, and that without any great cruelty, by feeding it with milk previous to its being strangled. Of all the barbarous methods of opening the animal while alive, the most useful seems to be that of Mr Hunter, who directs to perforate the small intestines, and throw in starch-water with solutions of musk, or indigo and starch water. "In a word (says Mr Sheldon), any gelatinous fluids rendered opaque with such colours as will be absorbed, are extremely useful for experiments of this kind; for much more may be seen by examining the vessels distended with a coloured fluid from natural absorption, than by anatomical

This to be done, a cork ought to be put into the pipe, to prevent the water getting into the vessel that is to be injected. Injection. tomical injection practised in the dead body." Liber- kuhn first discovered the ampullae by feeding chil- dren in whom the lacteal glands were obstructed pre- vious to their death with milk; by which means not only the lacteal trunks became distended with chyle, but likewise the ampullae. Thus absorbing mouths of the lacteal vessels were discovered by Liber- kuhn; and in a similar manner Afellius discovered the lacteals themselves. Thus also Eustachius discovered the thoracic duct in a horse; and Mr Hewson traced the lacteal vessels, lymphatics, and thoracic duct, in birds, by making ligatures on the root of the melon- tery, and other parts, which had been previously fed with barley. Mr Hunter likewise was enabled to ob- serve the lacteals of a crocodile when distended with chyle.

The coarse injection for the lymphatics is made of mutton-fat and yellow resin, in the proportion of two thirds of resin to one of fat. If required of a thicker consistence, we may add a small quantity of pure wax; if of a softer quality, we may augment the quan- tity of fat: Orpiment or king's yellow is generally made use of; though others are equally proper, provi- ded they be fine enough.

The instruments necessary for injecting the lympha- tic vessels are the injecting tube and pipes, lancets, blow-pipes, knives, scissors, forceps, needles, and thread. The old injecting tube has been found in a manner en- tirely useless, the pipe being fixed in a glass tube two or three feet long; which is one of the reasons why, before the time of Hewson, so little of the lymphatic system could be injected. Tubes of such a length are entirely unmanageable by one person, and it is impos- sible to perform the operation properly with two. To perform it in the best manner, the instrument should be held in the hand like a pencil or pen. The instru- ments used by our author are tubes made either of glass or of brass; which, when filled with mercury, may be held in the hand like a pen: a glass tube, however, is preferable to the metallic one. It is some- what in the shape of a trumpet; six inches and an half in length, an inch and an half broad where broadest, and three eighths of an inch where narrowest. A collar of steel half an inch broad and three quarters of an inch long is cemented to this pipe, and a smaller tube of the same metal is screwed upon the end of the collar; the whole terminating in a capillary tube about an inch in length. This last is the most difficult part of the whole work to execute; it should be drilled out of a solid piece of metal, and not made of a thin bit of plate soldered, as these are apt to turn ragged in the edges, and the folder is also liable to be destroyed by the mercury. Those used by Mr Sheldon were made by drilling a small hole lengthwise through a bit of well-tempered wire. It is cleaned by means of a very small piece of steel-wire capable of passing through the bore of the tube. This ought to be annealed lest it should break; in which case the broken bit could not easily be got out. Very small tubes may be made of glass drawn out as fine as we choose; and though very apt to break, they are easily repaired. They ought to be very thin, that they may be easily melted. Some- times it has been found convenient to fit the collar with a steel stop-cock.

The brass tube represented by our author is about nine inches and an half in length, and half an inch wide where widest. The collar is a full quarter of an inch broad, and three quarters of an inch long; a steel piece and capillary tube being screwed to it as in the other.

The lancets are to be exquisitely sharp, in order to cut into the lymphatic vessels. The latter are easily inflated by the small silver blow-pipes usually put up in the dissecting cases by the London mathematical in- strument makers; dissecting knives, fine pointed scissors, accurately made dissecting forceps, with straight or crooked needles, are likewise substituted with ad- vantage, as not being affected by the quicksilver.

We must next consider the proper subjects for injec- tion. Mr Sheldon recommends, that they should be as free from fat as possible; he has always found in the human subject those who died universally dropful, or of an affections or anaerobic, to be the best, for the following reasons, viz. in such there is little or no animal oil, and but a very small quantity of red blood; both of which, when they occur in great abundance, very much impede the discovery of the lymphatic ves- sels; but when the cellular vessels are loaded with wa- ter, the absorbents are more readily traced, and with less risk of wounding them in dissection: the prepa- rations also, particularly the dried ones, are more lasting. This circumstance is found to be of most conse- quence in preparing the absorbent vessels of the trunk and extremities of the human subject. Of all the vis- cera in young subjects, only the liver and lungs can be injected with success; and these may be successfully injected even in the fetus. It will be most pro- per to begin the operation upon the subject imme- diately after death, as lymph or chyle will then be more readily found in the vessels, than when we wait a longer time. In preparing the lacteals, previ- ously distended with milk in the living subject, it is proper to have the intestines and mesentery plunged (with the ligature upon the root of the latter) into rectified spirit of wine. This process will coagulate the chyle; and the fluid being opaque, the vessels will be beautifully seen when we mean to prepare the parts, by preserving them in proof-spirit as wet specimens: "In this way" (says Mr Sheldon) I have made in the dog one of the most natural preparations that can be seen of the lacteals injected from their orifices by the natural absorption." We may also prepare the lacteals by the method used by Mr Hunter, already mentioned; by which they will be very conspicuous, by the indigo absorbed from the cavity of the intestines. By tying the thoracic duct near its insertion into the angle formed between the subclavian and jugular veins on the left side, or by tying these veins on both sides, we may distend almost all the absorbents of the animal. Thus we are enabled to pursue these vessels in many parts where they have not yet been discovered, where they can scarcely be traced by injection, and even in some parts where it is utterly impossible for the injec- tions to reach them.

Another method sometimes successfully used by our author, was first practised by Malpighi. In this the part is to be steeped in water, and the liquid changed as long as it appears tinged with blood; suffering the parts afterwards to remain in the same water till the putrefaction begins. As soon as this begins to take place, the air which is extricated will distend the lym- phatics, phatics, so that they may be easily seen, and then injected with quicksilver. It is, however, remarkable, that this method will not in general answer so well in the human species as in quadrupeds; the air having never passed by putrefaction into the human lacteals in any of the subjects which Mr Sheldon tried, though it will take place in those of the horse or ass, and many other animals; drawing of the lacteals may likewise be made in this method to very great advantage.

In some parts of the human body also, this method may be employed to advantage; as the liver, heart, &c. It may likewise be useful to make ligatures on the large trunks of the vessels previous to the maceration, that thus the air may be confined as soon as it is extricated from the coats by putrefaction. Our author adds, that if ligatures were made upon the wrists and legs in articulo mortis, or immediately after death, the lymph would be stopped in the vessels, the latter would become distended, and might be injected with the greatest facility by the common method after taking off the ligature. Mr Sheldon in such a case recommends the tourniquet. "I have reason (says he) to believe, that absorption goes on as long as muscular irritability remains; which last continues a considerable time after the general life of the animal is lost." On this, however, we cannot forbear to remark, that making ligatures for such purposes upon a human creature in articulo mortis, or even immediately after death, savours so much of barbarity, that we cannot think it will be often practised. In some cases, even in the dead subject, ligatures are useful; as when we are searching for the lymphatics in the fingers and toes. In these it is useful to stroke up the parts with the finger, by which means the small quantity of lymph remaining in the vessels will be forced upwards, and stopped by the ligature; after which the vessels may be easily injected with quicksilver, as already mentioned.

To inject the vessels, we must open one or more of them, directing the point of the lancet almost always towards the trunk or trunks of the vessels, and taking care not to carry the incision through the opposite side. If the vessels happen to lie under the peritoneum as the lacteals, or under the pleura as the lymphatics of the lungs, we may cut into their cavity through these membranes. In injecting those of the extremities, however, and in many other parts of the body, it is absolutely necessary to dissect the vessels we design to fill away from the fat and reticular substance before we attempt to open them with the lancet. The tube with the pipe affixed to it is previously to be filled with mercury: the anatomist then inflates the vessel by means of the blow-pipe, takes the tube from the assistant, and introduces the small tube into the puncture. In this operation it will be found necessary not to carry the tube farther into the vessel than is sufficient to give the mercury a free passage; for if we introduce it farther, the passage of the mercury will be impeded by the pipe being pushed against the side of the vessel. Should not the fluid be able to effect a passage, it will then be necessary to press upon the surface of it in the tube with our fingers. If it descend freely, and without any of it passing between the side of the vessel and small pipe, we have only to fill up the tube with mercury as the latter descends; but if it gets out, we must then tie the vessel. This, however, should always be avoided if possible; because, if not very dexterously performed, the operator will be apt to separate the tube from the vessel; and on this account the puncture ought always to be very small, no larger indeed than is necessary to allow the pipe to get in with difficulty. As the injection proceeds, the pressure upon the surface of the quicksilver must be carried on higher and higher in the course of the lymphatic, till we come near the gland or glands into which the vessels terminate; otherwise we shall seldom get the cells of the glands, or the vessels emerging from the opposite side of the glands, well injected. In injecting the lymphatic vessels of the extremities, it will be useful to raise the part where the pipe is inserted higher than the other end of the limb, and to make the assistant press with his hands along the skin in the course of the vessels, which will favour the progress of the injection. When the vessels are sufficiently filled, which may be known by the swelling of them, and by the resistance the mercury meets with, the assistant passes a ligature about the vessel and ties it above the puncture before the anatomist withdraws the injection pipe.

The method of injecting the larger trunks or thoracic duct with the coarse injection is exactly similar to that already described for the sanguineous vessels. Mr Sheldon, however, recommends the use of some pipes of a particular construction invented by himself. The improvement consists in shaping the ends of the pipes like a pen; taking care to make the edges and point blunt, to avoid cutting the vessel when we introduce them. Thus much larger tubes than those commonly in use may be admitted; and there is no occasion to make any bulb or rising near the extremity of these small pipes to prevent the thread from slipping off; for this will certainly hinder us from inserting pipes of such diameter as might otherwise be done.

Having thus shown the method of injecting the lymphatics, our author next proceeds to describe the method of dissecting and preparing them either for immediate demonstration, or for preservation for any length of time. In the dissection, great care is requisite, on account of the exquisite thinness of their coats; but if this should happen by accident, it will then be necessary to introduce the pipe at the ruptured part; and having secured it above and below with ligatures, to fill it again as before directed. Our author recommends, for the purpose of dissection, such knives as are made use of by the Germans and French in tracing the nerves. They must be made thin in the blade like lancets, and not much larger. A variety of different shaped blades, some single and others double-edged, will be necessary for various parts of the body; the fault of the common dissecting knives being that they are too thick in the blade, which makes them soon blunt, and occasions the trouble of perpetual grinding, which is not the case with those just recommended. A sharp-pointed forceps is necessary, in order to lay fast hold of the smallest portion of cellular substance; but they ought not to be so sharp as to endanger the puncturing of the vessels; nor should they by any means be bowed or stiff in the spring, to prevent the fingers of the operator from being wearied in the operation. They should also be made in such a manner as to hold large as well as small portions of reticula. Injection. ticular substance. For dissections of this kind, fine-pointed scissors and lancets fixed in handles are sometimes necessary; and it is frequently of use to plunge the parts into water, in order to loosen the reticular membrane connected with the outside of the coats of the vessels; by which means they may be dissected more easily, and with less danger of wounding them. The blood may be extracted by frequently changing the water. After being injected with quicksilver, the parts should not be allowed to remain long in the water, because the volatile alkali formed by putrefaction is apt to change the colour of the mercury.

The dissection being performed, the preparation is then to be preserved either in a wet or dry state, according to its nature. Preparations of the larger parts, as the trunk or extremities, should be preserved dry; and to dry them effectually, they should be exposed to a free current of air, but not to the rays of the sun; and the vessels should be displayed in their natural situation. When fully dried, they ought then to be varnished over with transparent spirit or copal varnish; which will not only preserve them from insects, but render them more beautiful, and the vessels more conspicuous. They should then be inclosed in glass cases, where they are to be placed in a horizontal position, and handled as little as possible.

To make preparations of the thoracic duct, we must in the first place fill the aorta, vena cava superior, and vena azygos or intercostalis, with coarse injection; then fill, with the same, the vessels below the right crus or little muscle of the diaphragm. The duct is sometimes prepared with quicksilver; but Mr Sheldon recommends to anatomists to make drawings of anything new or remarkable in their preparations of the lymphatic vessels with quicksilver; as most of those specimens, particularly such as are dried, become at last totally useless by reason of the drying of the vessels and the escape or blackening of the mercury; or from the varnish growing more and more opaque with age. The quicksilver injection, however, in some cases is very useful. Thus, for instance, if we wish to demonstrate the valves in the thoracic duct, or any other large absorbent vessel, we need only inject the vessels with quicksilver, dissect and dry them, then cut them open, and let the mercury run out; after which the valves will appear by making sections in the coats of the vessels. This may be done still better by varnishing the vessels three or four times before the sections are made; because the varnish will strengthen the sides of the vessel. In wet preparations the valves in the cavities of these parts may likewise be demonstrated by opening them; or by inverting the vessels and suspending them in proof malt-spirits. Thus the valves that cover the terminations of the thoracic duct on the inside of the angle formed between the jugular and subclavian veins on the left side, and those which terminate the lymphatics on the right side of the neck, arm, and lungs, may be beautifully demonstrated. Specimens of the lacteal vessels, of the absorbents of the heart, lungs, liver, spleen, diaphragm, kidneys, &c., may be kept wet or dry, according to the particular nature of the preparation or view of the anatomist. Some preparations are the better for being dried and afterwards immersed in vials full of oil of turpentine; by which means the flesh will be rendered transparent, the vessels distinctly seen, and the vessels appear extremely beautiful. The only disadvantage of this method is, that the parts on which the vessels pass, do not at all preserve their natural bulk by reason of their shrinking up; and as the wet preparations are free from this inconvenience, Mr Sheldon does not hesitate at assigning them a decided superiority over the dry ones.—Sometimes it is necessary to fix the preparations upon stiff paper or pasteboard, on account of their weight after being injected with mercury. The paper or pasteboard on which they are fastened ought to be of various colours, according to the nature of the preparation, in order to form a proper ground for showing the lymphatic vessels. Such small preparations as are preserved in spirits, or oil of turpentine, may be kept in bottles well closed with stoppers; and the larger in common preparation glasses. Our author describes a simple method of stopping the mouths of these preparation glasses, by which means the stopper is rendered nearly as durable as the glass itself. "In order to execute it, let the anatomist take care to have the upper surface of his bottles made plane, by desiring the workmen at the glass-house to flatten them in the making. This they will easily do in forming the round ones, but the flat bottles are attended with considerable difficulty. The right way to make them, I believe, would be to blow them in moulds of various sizes; the workman should likewise form the bottoms of the bottles perfectly flat, that they may stand upright and steady. Bottles of this form being provided for the larger preparations, we grind the upper surface of them on a plain plate of lead, about a quarter of an inch thick, and two feet in diameter; first with fine emery and water, then with powdered rotten stone, or putty first wet with water and at last dry; so that the surface may be reduced to an exact horizontal plane, and of as fine a polish as plate-glass. This will soon be done, as the manoeuvre requires but little dexterity; and the anatomist should be provided with a considerable number of these glasses prepared as above directed. To the top of each bottle a piece of plate-glass, cut by a diamond, is to be adapted so as completely to cover, but not project over, the edge of the bottle. When these two smooth surfaces are put upon each other, with a drop of water between, the attraction of cohesion is so considerable, that it requires great force to separate them."

Many preparations of the lymphatics, and other parts preserved in bottles, do not require any strings to suspend them; particularly when fixed on pasteboard or paper; such as require suspension should be tied to strings fixed to the preparation below, and to small holes drilled in the substance of the glass at the bottom of the neck; or to small bits of glass that may be fixed on the inside of the same part. The preparation is thus suspended in limpid proof malt-spirit, the bottle being almost completely filled; the upper and polished surface of the bottle, and the plate of glass, are to be wiped clean and dry; a drop of solution of gum arabic is to be put on the polished surface of the bottle, the top strongly and steadily pressed upon it, so as to bring the two surfaces into as close contact as possible; after which the bottle is to be placed in a cool airy place to dry. A piece of wet ox-bladder, freed from fat, and soaked in water till it becomes mu-

G g z ciliaginous, is then to be placed over the top, the air pressed out from between it and the glass; after which it must be tied with a pack-thread dipped in the solution of gum arabic. The bladder being cut off neatly under the last turn of the thread, is then to be dried, the string taken cautiously off, and the top and neck painted with a composition of lamp-black mixed with japanners gold size: this soon dries, and leaves a fine smooth glossy surface, from which the dirt can at any time be as readily wiped off as from a mirror. By this method large bottles are as easily and effectually secured as small ones; and it is found to answer as well as the hermetical sealing of glasses, which in large vessels is altogether impracticable. If the bottoms have any inequalities which prevent them from standing steady, they may be easily made perfectly flat by grinding them with emery on the plate above mentioned. The tops, if well gummed, will even remain perfectly fixed on the glasses without the bladder: though in the common upright ones it may be advisable to put it on as a defence. Our author informs us, that since his making this discovery, he has used glass faucets; with flat tops gummed on. In these vessels the preparations, by reason of their horizontal posture, appear to great advantage. Thus he has exhibited very early abortions in their membranes, and some other preparations that cannot be suspended or viewed conveniently in the perpendicular direction. Some very delicate preparations, particularly those intended to be viewed with the microscope, those of the ampullae lacteae of Liberkuhn, and of the valves of the abortive, may be preserved either in spirits or dry in tubes closed in the manner just mentioned, and will appear to great advantage. Some of the dry ones may also be advantageously placed in square oblong boxes, made of pieces of plate or white glass neatly gummed together, with narrow slips of white or coloured paper, and the objects may be conveniently viewed in this manner. With respect to the stopper bottles, which are very convenient for holding final preparations, our author advises the stoppers to be perfectly well ground; that they pass rather lower down than the neck of the bottle for the convenience of drilling two holes obliquely through the inferior edge of the substance of the stopper, opposite to each other, for the convenience of fixing threads to hold the subject; for if the threads pass between the neck and stopper, a space will be left; or if the stopper be well ground, the neck of the bottle will be broken in endeavouring to press it down. On the other hand, if any space be left, the thread, by its capillary attraction, will act from capillary attraction, raise the spirits from the bottle, and cause evaporation, which will likewise take place from the chink between the stopper and neck.