(J. J. J.)

MEDICINE.

Medicine, in its most extended signification, may be said to comprehend all the knowledge which can be useful in enabling us to prevent the occurrence of diseases; or which may assist us, when diseases have occurred, in conducting their treatment, with a view to their alleviation or cure. The knowledge subservient to these several purposes (the prevention, alleviation, and cure of diseases) may be comprehended under three general heads: 1st, an acquaintance with the human economy in the state of health;—2d, an acquaintance with the various deviations from the healthy state, or, in other words, the various diseased, morbid, or pathological conditions to which that economy is liable;—and 3d, an acquaintance with those agents or powers which are capable of inducing disease in the economy, when it is in a healthy condition, and with those which are capable, when it is in a diseased condition, of restoring it to a state of health; that is, an acquaintance with what are termed morbific causes and therapeutic agents.

It is necessary to consider medicine both as a science and as an art. To the science of medicine it belongs to collect all the facts that have been ascertained respecting the operations and phenomena of the economy in its healthy and morbid conditions, and respecting the causes and remedies of diseases; to compare these facts with one another, so as to discover their mutual relations; to arrange them in a convenient order, and to deduce from them the general conclusions to which they may seem to lead; and to point out where the knowledge of facts is imperfect, and to suggest the means by which such deficiencies may be supplied. The art of medicine, again, consists in the immediate practical application of the knowledge that has been acquired by observation and experiment, in the several departments enumerated, to the prevention and treatment of diseases.

In the following article it is proposed in the first place to take a brief view of medical science considered in reference to the three departments which medicine has been said to comprehend. A similar view will afterwards be taken of those divisions which convenience and custom have established in medicine considered as a practical art. It is in the susceptibility of the economy to be affected with diseases, and in the influence which certain circumstances and agents exercise in producing their removal, that medicine, both as a science and as an art, has its primary origin. Diseases and their remedies, accordingly, must have been the first subjects of medical investigation that engaged the attention of mankind. The importance of a correct acquaintance with the human economy in a state of health could come to be felt only after these practical branches had made some degree of advancement. It is now, however, well understood that the extent of knowledge which can be acquired respecting the human economy in the state of disease, must in a great measure be dependent upon the knowledge that is possessed of that economy in the state of health; since the very groundwork on which all rational inquiries respecting diseases must ultimately rest, is the knowledge of the circumstances in which the economy that is disordered, differs from the same economy in a sound condition.

I. As the human economy consists of two distinct elements, an organised body and a conscious mind, which, whatever may be the nature of their connection, exercise most important influences on one another; and as both of these elements of the economy are liable to experience deviations from their natural or healthy condition, a knowledge of the body and of the mind, in the healthy exercise of their functions, forms the essential foundation of medical science.

The study of the mind, in its healthy condition, has usually been regarded as constituting a particular department of philosophy (psychology) quite independent of medicine; but we shall afterwards find reason for believing that the consideration of its various phenomena, intellectual and moral, ought to be included under the same department of medical science that treats of the healthy phenomena of the corporeal part of the economy.

The knowledge of the organised body, in the state of health, is of a two-fold nature; first, as it relates to the structure of its several parts; and, secondly, as it relates to the use, purpose, or function which each part performs in the economy, and to the reciprocal dependence of the different functions on one another. The two branches of medical science that treat of the structure and functions of the body, are comprehended, as every one knows, under the names of Anatomy and Physiology; branches which are, no doubt, most closely allied, and in some respects inseparably connected with one another, but which are at the same time sufficiently distinct in their objects and in their means of prosecution, and sufficiently extensive in the field of investigation which each of them presents, to admit of, or rather to require, separate consideration in any view of them tending to be systematic.

To each part of the body capable of performing some particular function or purpose in the human economy, the name of organ is usually assigned; thus the eye is said to be the organ of vision; the stomach and intestines with the liver, pancreas, &c., the organs of digestion; and the muscles, bones and joints, the organs of voluntary motion. In examining the structure of the different organs of the body, it is found that they all consist of different anatomical elements; and whilst some of these elements vary in the different organs that are examined, others of them are met with in all the organs indiscriminately. Thus if we compare the structure of the heart and of the liver, we shall find in the former, layers of muscular fibres of which no trace can be observed in the latter organ; while in the liver, on the other hand, we find a peculiar arrangement of cellular matter, usually denominated parenchyma, to which nothing analogous is discoverable in the heart. In both of these organs, however, vessels, for the conveyance of blood and other fluids, and nervous filaments can be discovered; and these latter anatomical elements, the vessels and nerves, pervade, in greater or less number, all parts of the animal frame. Whilst each bone and each muscle may be said, in some sort, to have a separate existence, independent of every other bone or muscle of the body, every blood-vessel and every nerve, on the contrary, exists only as a part of a general system, all the ramifications of which are connected with one another through the medium of a central organ or part. Those anatomical elements which vary in the different organs of the body, such as muscular fibre, cellular substance, mucous and serous membrane, &c., are denominated textures by anatomists; whilst those which are constant in all the organs, the blood-vessels, lymphatics, and nerves, are regarded as parts of their corresponding systems.

There are several different points of view in which the structure of the human body may be considered. 1st, We may examine the different classes of organs and the different systems separately, confining our attention principally to the relations which the different organs of the same class, or the different parts of the same system bear to one another; the bones, the muscles, the vascular system, the nervous system, &c., each being treated of under a distinct head. It is in this view chiefly that the structure of the body is considered in what has been termed Descriptive Anatomy. 2nd, We may consider the relations which the different organs and systems entering into the composition of any particular region of the body, bear to one another, as, for example, the relations of the muscles, blood-vessels, and nerves of the neck; or the relations of the parts of the perineum to one another and to the lower part of the bladder. It is this kind of anatomical knowledge, (the anatomy of the regions, as it has been termed), which is essential in the performance of surgical operations, and which has hence frequently received the name of Surgical Anatomy. 3d, We may examine into the minute structure of each of the different kinds of organs and parts of systems, as of the stomach, liver, heart, arteries, brain, nerves, &c., and endeavour to ascertain in relation to each, whether it consists of one or of several elementary substances or textures, what is the physical arrangement of each of the textures entering into its composition, and in what manner these are united and combined. To this minute investigation of the structure of the different organs and systems of the body, and of the textures entering into their composition, the name of General Anatomy has been assigned. 4th, We may compare the different parts of the human frame, as the nervous or vascular system, the respiratory or digestive organs, &c., with the corresponding parts of other animals, a comparison which frequently leads to an improvement and extension of our knowledge of the structure of the human body. To this field of inquiry the name of Comparative Anatomy has been given. And 5th, We may enquire into the progressive development which the body and each of its parts undergoes during the embryo and foetal states, from its earliest period of formation to the time of birth; a branch of investigation which has received the name of the Anatomy of Development, and which is equally applicable to man and to the lower animals.

When we reflect on the length of time during which the structure of the human body has been the subject of investigation, the number of persons who have been engaged in the inquiry, and the enthusiasm with which it has been prosecuted, it may appear strange that there should be still many anatomical points respecting which we are aware that our knowledge is very deficient; and that from time to time facts are brought to light, in this department, of which no previous suspicion had been entertained. Anatomical discoveries, as appears from the foregoing observations, may relate to the textures, to the systems, to the organs, or to the regions of the human body; or they may relate to the structure of the lower animals, or to the gradual development of animal bodies during their foetal existence.

1. The anatomy of textures is comparatively a recent investigation, for though it cannot be said to have originated with Bichat, yet unquestionably it received from him the dignity of a separate branch of scientific inquiry; not only from his having contributed materially to its advancement by his own labours, but from his having by the ingenious and philosophical views which he took of the subject, rendered the medical profession more fully aware of the important ad- vantages to be derived from its cultivation. But besides being of recent origin, the anatomy of textures is a subject attended with very considerable difficulties from the minuteness of the objects to be investigated. As illustrating these difficulties, we may refer to the various statements which have at different times been given respecting the primary structure of muscular fibre, of bone, and of nervous substance. And as the principal means by which we are assisted in overcoming them, may be mentioned in the first place, the employment of chemical re-agents, by which, in some instances the parts are rendered more fit for examination by being hardened, as is, for example, the case with the substance of the brain; and in other instances the structure of the part is ascertained by one texture being destroyed whilst another is left entire, as in the case of the bones and nerves. As a second means of overcoming the difficulties attendant on the anatomical investigation of textures, may be mentioned the use of the magnifying glass and of the microscope. The latter instrument, which was invented about 1620, seems to have been first applied to purposes of anatomical investigation by Malpighi, who was followed in this line of research by Hook, Power, Leuvenhoek, and Lieberkun. In later times it has become an essential part of the apparatus of the anatomist.

2. The discoveries relative to the anatomical systems, which have from time to time been made, and which may be expected to be still further extended, refer to the minute ramifications of the vessels and of the nerves; to the modes in which the different kinds of vessels, arteries, veins, capillaries, and lymphatics communicate with one another; and to the connections of the minute filaments arising from different nerves. The prosecution of this department of anatomy, in particular, has been most materially advanced by the invention of the art of injections. "In the latter part of the last century," says Dr. Hunter, in his introductory lectures to his last course of anatomy, "this science made two great steps, by the invention of injections, and the method of what we commonly call preparations. These two modern arts have really been of infinite use to anatomy; and besides, have introduced an elegance into our administrations which in former times could not have been supposed to be possible. They arose in Holland under Swammerdam and Ruyssch, and afterwards in England under Cowper, St. Andre, and others, where they have been greatly improved. And from England, they are of late years spreading to all parts of the British dominions, to France, Italy, and other parts of Europe. I say, from England, because the arts of making fine injections and preparations seem to have been almost peculiar to Holland and England, and the anatomists who have excelled in that way have generally made a secret of their methods and improvements, till within the last thirty years, when all these arts have been constantly taught in public courses of anatomy here."

3. The anatomy of the organs, and particularly of some of the internal viscera, as the brain, the liver, &c., notwithstanding the repeated investigation to which they have been subjected, still presents an extensive field of inquiry; for much remains to be ascertained as to the textures that enter into the composition of each organ, and as to the relations of these textures to one another, and to the ramifications of the systems with which they are more or less largely combined.

4. In the anatomy of regions, the objects of investigation are on comparatively a large scale, and consequently more easily discovered and appreciated. Yet structural arrangements modifying the progress of surgical diseases, and regulating the performance of surgical operations, still continue from time to time to be brought to light. The improved knowledge that is at present possessed of the anatomy of the parts concerned in hernia, and in the operations of aneurism and of lithotomy, bears honourable testimony to the diligence and skill with which this department has in modern times been prosecuted.

5. Comparative anatomy, though from the name it bears, it obviously originated in the comparison of the structure of the human body with that of other animals, has in its progress come to form a science in itself; and when we consider the number of animals already known, the additions that are from time to time made to these, by those who are engaged in exploring distant regions of the globe, and the increased facilities of obtaining specimens for the purposes of dissection, afforded by voyages of commercial or scientific enterprise, it is not wonderful that this department should every day be presenting a rich harvest of discovery to reward the industry of those who are engaged in its cultivation.

6. The anatomy of development, notwithstanding the zeal with which it has, in modern times particularly, been cultivated, still affords an extensive field for the collection of curious and interesting facts. From the ease with which observations may be made on the eggs of birds, during the progress of incubation, many anatomists have availed themselves of the opportunity thus afforded for studying the development of the fetus and its several organs. But it was not till a very late period that their observation was extended to the formation or evolution of the organs in the other classes of vertebrated animals. It is satisfactory to know that the more the structure of the ova of the different classes of vertebrated animals has been studied, the more perfect has the resemblance between them appeared to be. "Since our acquaintance with the development of the ovum has increased," says a late writer on this subject, "the mode in which the organs of the fetus are produced, has been proved to be analogous, in the different classes of vertebrated animals; and we are induced to believe that a knowledge of the simpler forms of these animals must greatly facilitate our study of the more complicated." We may remark that there are two leading views, in conformity with one or other of which the investigation of this department of anatomy has been prosecuted. According to the one view, the impregnated ovum, or original germ, before the process of development has commenced, contains already formed all the parts which are afterwards to be found in the perfect animal; so that the successive appearance of the organs of the animal, which is observed during the progress of development, is owing simply to the evolution, or coming into sight, of parts which had previously been invisible, in consequence of their small size and of their transparency. According to the other view, the original germ, before development has commenced, is very simple in its structure, and does not, so far as can with the greatest attention be discovered, contain any part that can be compared to the fetal or adult animal, so that during the development of the fetus, its organs are actually formed, and not simply evolved. Those who entertain this opinion accordingly maintain, that several of the organs of the embryo can be seen gradually forming by the apposition of their parts. Closely allied with the anatomy of development is the inquiry relative to the various malformations or monstrosities which animal bodies occasionally exhibit; for according to the notion that may be adopted respecting the primitive condition of the germ, and the changes which it subsequently undergoes, will be the view entertained as to whether the occurrence of monstrosities is attributable to some peculiarity in its original structure, or to some imperfection or irregularity in its development. And in proportion as our knowledge shall be extended, of the relative periods at which the different organs are formed, and of the successive series of changes which they undergo, will we be the better able to analyse and comprehend the modes in which monstrosities are produced.

Besides the consideration of the functions of the corpo-Physiology. real part of the economy. Physiology comprehends likewise, as has been already hinted, that of the phenomena of mind. All these phenomena, or operations of the human economy, corporeal and mental, it has been found convenient to arrange under three classes of functions, designated by Galen, the Natural, the Vital, and the Animal. Under the Natural are included those functions which are performed by all organised beings, plants as well as animals, and which are essential to the preservation of the individual, and the continuance of the species; the functions, namely, of nutrition and reproduction. The Vital class of functions comprehends two, which, in the higher orders of animals at least, cannot be suspended for more than a very short space of time, without putting a stop to life; the functions of circulation and respiration. The Animal functions are those by the exercise of which the animal creation is particularly characterized, but which vary in their degree and perfection, according to the place the animal occupies in the scale of existence; the functions of sensation, thought, and volition.

On an analysis of all the phenomena which these several functions exhibit, it will be found that these phenomena are of three kinds. In the production of some, corporeal organs only are concerned; others are wholly of a mental character; and others, again, are partly mental and partly corporeal. The corporeal operations of the human economy, as regards their results, are physical or chemical, that is, they consist in changes in the relative situation of sensible particles, unattended with change in their composition; as when the blood is conveyed from the heart throughout the whole fabric of the body, and again returned to the central organ of circulation; or they consist in changes in the combinations and arrangements of elementary particles; as in those changes of deterioration and purification which the blood undergoes during its progress through the greater or systemic, and the lesser or pulmonic circulation. There are several operations of the economy, of which the present state of our knowledge does not enable us to determine whether they be properly of a physical or of a chemical character; as, for example, those processes by which various fluids are separated from the blood, in the different organs of secretion. As regards their causes, the corporeal phenomena of the animal economy seem to be partly dependent on the common properties of inorganic matter, as gravity, weight, elasticity, chemical affinity, &c.; and partly on vital properties peculiar to animal bodies, more particularly the irritability of the muscular fibre, and the energetic influence of the ganglionic system of nerves.

With respect to the phenomena of the human economy that are wholly mental, "there is," as was well observed by the late Dr. Thomas Brown, "a physiology of the mind as there is a physiology of the body; a science which examines the phenomena of our spiritual part simply as phenomena, and from the order of their succession, or other circumstances of analogy, arranges them in classes under certain general names; as in the physiology of our corporeal part, we consider the phenomena of a different kind which the body exhibits, and reduce all the diversities of these under the names of a few general functions." A knowledge of the intellectual and moral powers, though their investigation forms the peculiar province of the metaphysician and moral philosopher, is essentially necessary to the physiologist, both from their own importance as parts of the constitution of man, and from the powerful influence which they exercise over his bodily functions. It is obvious, likewise, that a knowledge of the mind in its healthy exercise must be equally necessary to a proper understanding of mental diseases, as is a knowledge of the body in the state of health to the understanding of its diseases. It is gratifying, therefore, to find that medical men are becoming more and more aware of the importance of acquiring such a knowledge of the operations of the intellectual faculties and moral feelings as may serve as a groundwork for the scientific study and humane treatment of mental diseases. The most interesting point of view, certainly, in which the mental phenomena present themselves to the consideration of the physiologist, is in their connection with the nervous system. It is well known that while some physiologists are content with recognizing a general connection between the faculties of the mind and the brain, others have endeavoured to establish a more especial relation between particular mental powers and particular parts of the cerebral organ.

Of the phenomena of the economy in the production of which the mind and body are both obviously concerned, a part, those, namely, of sensation, originate in the body and are concluded in the mind; whilst another part, those, namely, of voluntary motion, originate in the mind, and are concluded in the body. In each of these two functions, the nerves seem to serve as the medium of communication between the brain, as the more immediate organ of the mind, and the different sensory and motory organs of the animal frame.

The progress of physiology is necessarily dependent on its sources the advancement of other collateral sciences, particularly of improvements of anatomy and of chemistry, as well as on experimental research. A few illustrations of the advantages that have accrued to physiology from the improved and extended cultivation of each of these departments, may serve to place this dependence in a clear point of view.

1. As to the influence of anatomy on the advancement of physiology, we may observe, that to know the action or operation of a machine, it is essential to know its mechanism or structure; and to those conversant with this kind of inquiry, nothing in many instances is requisite but a knowledge of the relative situation and the connection of parts, to enable them to comprehend the general effect which will result from their combined action, and the particular share which each part contributes towards its production. There can be no doubt that the circumstance which first directed the attention of the illustrious Harvey to those investigations which terminated in the discovery of the circulation of the blood, the most important physiological discovery certainly that has ever been made, was his desire to ascertain the use of the valves of the veins, the existence of which had been pointed out to him by his distinguished teacher in anatomy, Fabricius ab Aquapendente. It is obvious, too, how great a difference in the knowledge possessed of the function of assimilation must have been produced by the discovery of those absorbent vessels, the lacteals, as they have been termed, that convey the digested food or chyle from the intestinal canal along the mesentery, to the common trunk named the thoracic duct, which ultimately discharges it into the venous system. It was not till 1622 that the lacteal vessels were discovered by Gaspard Aselli at Cremona, and twenty-five years elapsed subsequently to this before Pecquet of Dieppe discovered, at Montpellier, the thoracic duct. Previously to that time it had been supposed that the chyle is conveyed by the veins of the mesentery from the intestines to the liver, and that it is the peculiar function of this organ to convert that fluid into blood.

2. Many illustrations might be given of the lights which chemical science has in modern times thrown upon the phenomena and functions of the animal economy. The reciprocal changes which the atmospheric air and the blood produce upon one another within the lungs, in respiration; the changes which the food undergoes from the action of the different fluids with which it comes in contact in its passage through the alimentary canal; and the composition of the different products of secretion, as the gastric juice, the bile, and the urine, are amongst the more remarkable objects of physiological inquiry, to the advancement of the knowledge of which chemistry has powerfully contributed.

3. Every function of the body furnishes a host of in- stances in which our knowledge of its mode of performance and of its reciprocal dependence upon, and influence over, the other functions, has been advanced by experimental researches. None of these researches, perhaps, are more important in the conclusions to which they have led and still promise to lead, or have been prosecuted with greater diligence and sagacity, than those which relate to the dependence of particular functions upon particular portions of the nervous system.

II. Such, then, are the two points of view in which it is necessary for the purposes of medical science to consider the human economy in the state of health; first, in relation to the structure of the body and its several parts; and second, in relation to the actions or functions of these parts, or the corporeal and mental phenomena of which the human economy is the field of operation. But it is in precisely the same points of view that it is necessary for us to consider the economy in the state of disease. There is a department of Morbid as well as of Healthy Anatomy, and a department of Morbid, as there is one of Healthy Physiology. These two departments considered separately, and in their relations to one another, constitute the branch of medical science denominated Pathology. As it is the object of Healthy Anatomy to make us acquainted with the structure, forms, dimensions, and connections of the several textures, systems, and organs of the body, in the state of health; so it is the object of Morbid or Pathological Anatomy to make us acquainted with the changes in all of these respects, to which the different parts of the body are liable in the state of disease. And in like manner, as it is the object of Healthy Physiology to make us acquainted with all the several phenomena, corporeal and mental, that are taking place in the human economy in its healthy condition, to trace the causes from which they originate, the mechanism by which they are accomplished, and their reciprocal dependence and influence on one another; so it is the object of Morbid or Pathological Physiology to ascertain to what deviations the several corporeal and mental phenomena are subject in the state of disease, and to discover what new phenomena are developed in that state, and by what powers or agents these deviations are occasioned.

No department of medical science, probably, ever received so large an accession of materials for its elucidation, in so short a period of time, as morbid anatomy has done, since medical men became fully aware of the benefit which Theoretical and Practical Medicine is capable of receiving from the investigation of those various morbid alterations of structure that occur in the different organs of the human body. There are three principal points of view in which the knowledge obtained by necropsical examinations may be considered; and were we to trace the history of Pathological Anatomy, it would be easy to show that the consideration of that knowledge in these different points of view marks the successive epochs in the progress of this department of medical science.

1. Pathologists may endeavour to ascertain the various morbid alterations that occur in the structure of the different textures, systems, and organs of the body, in the progress of particular diseases, as of fevers and febrile eruptions, of tetanus or locked jaw, or of consumption, &c. The Observationes Medicae Rariorum de Schenckius, published at Frankfort in 1600; the Sepulchreum sive Anatomia Practica or Caudaevisus morbo denatis of Bonetus, published at Geneva in 1679; and the Epistle de Sedibus et Causis Morborum per Anatomiam indagatis of Morgagni, published at Venice in 1761, though differing widely from one another in importance and merit, may be regarded as all belonging to this first period of Pathological Anatomy, seeing that they all consist, for the most part, of individual cases of disease, arranged in a systematic order according to the part of the body which had been principally affected.

2. They may consider each particular texture, system, or organ of the body, (as, for example, serous membrane, the heart and blood-vessels, or the stomach and intestines), separately, and without reference to individual cases of disease, in relation to the various morbid changes of structure which it is liable to undergo, (such as inflammation and its consequences, morbid degenerations and new growths,—and with a view to the effects which these changes produce on the performance of the functions of the particular texture, system or organ. As illustrations of this mode of considering Morbid Anatomy we may refer to the systematic works of Ludwig, Baillie, Couraud, Voigtel, and Otto. The recent investigations respecting the morbid alterations of structure that occur in the different portions of the nervous system, in the heart and blood-vessels and in the organs of respiration, are most creditable proofs of the diligence and success with which this department has been prosecuted in the course of the present century.

3. They may consider each particular kind of morbid structural change, (as inflammation, tubercle, cancer, &c.), as a separate subject of examination, in respect of the general characters which it exhibits from its first development till its termination or the death of the individual, in all the parts of the body in which it is liable to occur, and the modifications it exhibits in each particular texture or organ. It is by the greater degree of attention bestowed upon this department, that the pathological anatomy of the present day is more particularly distinguished from that of former times. But though great additions have recently been made to our knowledge of morbid structures, as for example, in what relates to the development of tubercle, by the works of Bayle, Laennec, and their followers; to the distinctions between scirrhus and fungus hematoide, or hard and soft cancer, by the writings of Hey, Burns, and Wardrop; and to the existence of morbid structures not previously known, such as melanosis; a great deal still remains to be accomplished before this branch of medical science can be considered as placed upon a satisfactory footing.

The means by which our knowledge of morbid structure has been extended, and may be expected to be still further advanced, are the same as those upon which the progress of healthy anatomy depends; frequent dissection of the dead body, and the employment of those physical and chemical aids to which we had formerly occasion to refer.

A circumstance which has materially assisted in diffusing a knowledge of the morbid alterations of structure which the different textures, systems, and organs of the body are liable to undergo, has been the formation in anatomical museums, of collections of specimens of diseased parts. These collections seem to have consisted at first, chiefly or solely, of such substances as could be preserved in a dry condition, such as macerated bones, calculi, &c.; but their value has been greatly increased in later times, by the collectors availing themselves of the art of making wet preparations. Within a still more recent period an important advancement has been made in the application of the pictorial art to the illustration of pathological anatomy. It is long indeed since it has been customary to represent in engravings, detached specimens of diseased parts, particularly of those which exhibit considerable change of form on the external surface of the body; and some valuable works had been published, in which particular branches of pathological anatomy had been considerably advanced by illustrations of this description. The "Series of Engravings, intended to illustrate the Morbid Anatomy of some of the most important parts of the human body," which was published by Dr. Baillie at the beginning of the present century, is alike distinguished by the sound judgment displayed in the selection of the subjects, and by fidelity and beauty in their representation. But it has been of late years only that pathologists have called in the aid of colouring to assist in conveying an idea of the changes which disease induces, not only on the surface of the body, but in each of its different textures, systems, and organs. And when it is considered how important an element colour forms in the characters by which the different morbid alterations of structure are distinguished; and how seldom it is possible to preserve any traces of it in preparations, it must be obvious how much coloured delineations are calculated to aid in communicating a knowledge of pathological anatomy, by conveying to the mind, speedily and precisely, through the medium of the eye, appearances of which the most lengthened verbal descriptions can enable the reader or hearer to form only a very imperfect conception.

Of the light which the improved knowledge of morbid alterations of structure has thrown upon diseases and their treatment, we shall afterwards have occasion to speak; at present we may remark, that as morbid anatomy has been promoted by the gradually improving acquaintance with the anatomy and physiology of the body in the state of health, it has in its turn materially assisted in elucidating many obscure and difficult points in these two departments of medical science. The processes of disease, indeed, not unfrequently fulfil the same purposes as the experimental measures to which anatomists and physiologists are wont to have recourse, in prosecuting their respective investigations. Of this many striking illustrations might be found in the injuries and diseases of the different portions of the nervous system.

As an importantly of pathological anatomy, in the investigation of disease, it is proper to mention pathological chemistry, or the application of the knowledge that has been acquired, respecting the composition of the different solids and fluids of the body, to the discovery of the morbid changes which they are liable to undergo. Our knowledge of the results of morbid action has already received very considerable and valuable additions through the means of this department of scientific research. Amongst the benefits for which we are indebted to it, may be mentioned the replacement of the vague and conjectural art of Uromancy, by a body of precise information relative to the various morbid changes which the urinary secretion experiences in the diseases of its own peculiar organs, or in those of other parts of the body.

Before proceeding further in this general view of that department of medical science which relates to disease, it may be proper briefly to state the import of two terms of which we shall have frequent occasion to make use, namely, symptom and proximate cause, and to point out the principal varieties of symptoms and proximate causes, as they present themselves to the consideration of the pathologist. By a symptom, then, is meant any phenomenon or circumstance which leads us to infer that some one or other of the functions of the economy is not exercised in its ordinary or healthy manner. Of these circumstances a knowledge may be acquired in three ways: 1st, through the information of the patient; 2d, by direct observation; or, 3d, by experimental investigation. Of each of these modes of recognizing or discovering symptoms, we shall offer a few illustrations.

1. We know that a person in health sees objects single, and does not experience any sensations of sound unless his ear be exposed to atmospheric vibrations. But if a patient tells us that he sees objects double, and has ringing in his ears,

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1 Professor Lerdat de Montpellier, in his Essai sur l'Anatomie Medicale, ou sur les Rapports d'utilité entre l'art du Dessin et l'étude de la Maladie (1836), has given a brief but interesting outline of the connection which has subsisted between anatomy and the fine arts, particularly painting and engraving, in the successive periods of their progress; and has with great justice represented the art of engraving as having most powerfully contributed to advance the knowledge of anatomy. M. Lerdat has thrown out some ingenious reflections, too, on the applicability of painting to the representation of what may be called the phaenomenon of disease; that is, the changes it produces on the outward appearance of the frame. He does not, however, seem to have even dropped an incidental allusion to the applicability of delineation to the illustration and advancement of pathological anatomy. The advantage that might result from the application of coloured delineations to the representation of diseases was fully pointed out by Professor Delius, in his Meditatio de Iconibus Pathologico-Anatomiae ad Notarum pictis, published at Erlangen in 1782, along with his treatise De Cholelithia, in which he gives a coloured plate representing gall-stones. According to the former of these views then, a disease consists in a determinate group of symptoms observed to occur, in combination or succession, in a number of individuals; according to the latter a disease consists in a determinate deviation of some part of the economy from its healthy structure or function, in some determinate proximate cause.

Much has been said and written lately, in some medical schools, of the great superiority of the plan of investigating diseases with a view to the pathological conditions on which they depend, over that which principally occupies itself with the examination of the symptoms which they exhibit. It does not appear to us, however, that there is either necessity for, or justice in, depreciating the one branch of inquiry in order to exalt the other. It must be the object of an enlightened cultivator of medical science to obtain every information in his power respecting diseases considered both in reference to the symptoms which they exhibit, and to the pathological states, morbid conditions or proximate causes on which they depend. However great the difficulty may be of accurately marking the symptoms of diseases, that of referring them to their proximate causes is infinitely greater, and it is not therefore to be wondered at, that these two branches of inquiry are not equally advanced. But because we have become more sensible of the importance of being acquainted with those elementary changes in structure and function on which deviations from the healthy condition of the economy depend, we are by no means entitled to speak slightingly of the labours of those, who by their diligent and accurate examination of diseases, in reference to the more or less regular combinations and successions of symptoms, have demonstrated the necessity of, and prepared the way for, this other branch of medical inquiry.

In pathology, or the investigation of diseases, as in the Progress of other departments of inductive philosophy, the order in investigations which those proceed who attempt to extend the limits of human knowledge, and that which is followed by those who are endeavouring to communicate to the uninformed the acquisitions that have already been made in this branch of medical science, are essentially different. In their original investigations, pathologists seek to advance from the knowledge of individual facts respecting morbid structure and morbid function, to the establishment of general principles; whilst in their instructions they commence with the exposition of general principles, and descend from these to the enumeration of the particular facts which these principles connect, or which, to use the ordinary language, they serve to explain.

If we carry ourselves back in imagination to the earliest ages of medicine, we shall be sensible that it was only in the examination of individual cases of disease that the pathological studies of the practitioners of those days could consist. But by comparing the cases that fell within their observation, they would be led to notice various circumstances in which they resembled or differed from one another. If we could suppose them to have attempted to record the histories of these cases, they must have found that the work involved them in a great deal of repetition, from the similarity of the symptoms which presented themselves in a number of different individuals; a similarity that must have appeared the greater to these early observers, from its being only the outstanding or prominent features of the cases to which their attention would be given. On the observation of such a similarity amongst individual cases, must have been founded the recognition of particular diseases, such as ague, rheumatism, apoplexy, pleurisy, and dysentery, a specific name being given to every combination or series of morbid phenomena that was observed to occur with considerable regularity in a number of different persons, just on the same principle as a specific name is given to every other group of objects which exhibit a general correspondence in their qualities or characters. It must have been in this way that the transition was made from the consideration of individual cases of disease to that of particular diseases, and that the pathologist of those early times, instead of confining himself to drawing up an account of each single case in all its minutest details, would be led to generalize the results of many similar cases; first, perhaps, in relation to particular circumstances of their history, and afterwards in relation to their whole course or progress, so as ultimately to produce a delineation exhibiting those more prominent and more important characters in which the whole group of cases agreed, without its being overloaded with the trivial and accidental circumstances peculiar to each.

To designate that branch of pathology which is occupied with the detailed description of particular diseases, (the Prima Medicina see Historia Morborum of Baglivi,) no more suitable term perhaps has been invented than that of Nosography, employed by M. Pinel. The marking of those phenomena and circumstances by which particular diseases are especially characterised, has long been considered as a peculiar branch of medical inquiry under the name of Diagnosis.

But the processes of comparison and contrast which were necessary for establishing and describing particular diseases, must have called the attention of medical men to a number of points in which different diseases correspond with or differ from one another; and thus have opened up to them views of disease extending not only beyond the consideration of individual cases but even beyond that of particular diseases. Thus, when it was found that the same individual symptom, such as quickness of pulse, headache, cough, vomiting, or purging, may occur in several diseases, which in other respects differ very essentially from one another, this observation would suggest an inquiry as to the different conditions of the economy in which each particular symptom of disease may occur; and in this manner would be established a general doctrine in medical science, having for its object to consider individual symptoms of disease in all their various relations; a department of inquiry to which the names of Semeiology or Symptomatology have been assigned.

To the friends of the sick it is naturally an object of great anxiety, at as early a stage of their malady as possible, to be able to anticipate its ultimate result as well as general progress, and the more striking phenomena which it will exhibit in its course; and the skill of the medical practitioner is in a great measure estimated by the bystanders, according to the accuracy of his predictions on these subjects, or, as it has been termed, of his prognostics. To be able particularly in the early periods of diseases, from the contemplation of the present to anticipate the future, when to the unpractised eye every thing seems involved in general obscurity and doubt, has accordingly been at all times a very favourite object with medical men; and those who are acquainted with the writings of the father of medicine must know how large a share of them is occupied in laying down rules to guide the practitioner in the formation of his prognostics, principally founded on the results of his own extended observation. No portions of his writings, indeed, more fully justify, than those which relate to Prognosis, the eloquent observation of M. Prunelle, that "the works of Hippocrates present the most striking application of that philosophic method, which, creating axioms out of observations, and transforming the results of particular facts into general rules, furnishes the human mind with the most active instrument for perfecting the sciences." The anticipations of the medical practitioner respecting the future progress of individual cases of disease must, it may be remarked, be founded on the occurrence of particular single symptoms, or of particular combinations of symptoms, and must be influenced in many cases by the constitution of the individual affected, or by the external circumstances to which he has been or is subjected, such as the prevailing atmospheric constitution, or the character of the reigning epidemic.

It must soon have been found that it is not individual symptoms only that are liable to occur in several different diseases; but that certain determinate combinations of symptoms may be common to diseases which nevertheless are marked as different from one another by the other symptoms with which, in each of them, these common phenomena are combined. Such, for example, are the particular groups of symptoms by which fevers, inflammations, haemorrhagies, dropsies, &c., are characterised, each class comprehending a number of diseases, which all correspond to a certain extent in the symptoms by which they are accompanied, and at the same time all differ widely from one another in other respects, according to the particular organ which may be the more immediate seat of disease. The observation of such general analogies or resemblances in the symptoms of different diseases, and the employment of general terms to designate them, would suggest to medical men the idea of classing diseases in more or less numerous families or groups, such as those which we have just named. Other grounds of classification would be found in the resemblances or differences of particular diseases in regard to their general course and ultimate result, suggesting such distinctions of diseases as those into acute and chronic, continued and intermittent, mild and malignant, &c. It has been, however, in comparatively recent times, that the classification of diseases, combined with their nomenclature and definitions, has been erected into a separate department of medical science under the title of Nosology.

In watching the various preternatural phenomena which proximate the several functions of the economy are liable to exhibit in cases, the state of disease, medical men are naturally led to consider what the changes in the internal conditions of the corresponding organs of the body can be, which give rise to those deviations from the ordinary exercise of the functions, that constitute the symptoms of diseases. The attempt to ascertain the internal conditions of the economy on which the external phenomena or symptoms of diseases depend, or, in other words, to ascertain the proximate causes of diseases, though it has unquestionably involved medicine in much unprofitable, or rather injurious speculation, is as legitimate and necessary a subject of investigation as any other department of the science. It has been in the attempts of medical men to arrive at extensive generalizations of the proximate causes of diseases, whilst their observations were still too imperfect and too inaccurate to serve as a foundation for such attempts, that the various systems of medicine have had their origin, which have at different times been proposed. A very slight analysis of these various systems, would, we believe, be sufficient to shew that however great may be the diversity of opinion which they seem to embrace, they are all founded upon a few leading assumptions which may perhaps be expressed in the following propositions:

1. That diseases depend upon morbid changes in the general chemical composition of the different parts of the body, and theories of particularly of its fluids. This principle forms a prominent feature in the doctrine of the four humours entertained by Hippocrates; in that of salt, sulphur, and mercury, adopted by Paracelsus; in that of ferments, suggested by Van Helmont; in that of acid and alkali, maintained by Sylvius; and of those other doctrines founded upon the more accurate knowledge of chemical elements that has been obtained in modern times, which have been proposed by Baumes and others.

2. That the physical conditions of the solids and fluids of the body, furnish the proximate causes of diseases. This has served as the principal groundwork for the doctrines of the medico-iatro-mathematicians, Borelli, Bellini, Bag- Disease. livi, &c.; but it may be traced back to a much earlier origin in the Methodic school of medicine, founded on the corpuscular or atomic system of philosophy; in the hypothesis of Asclepiades respecting the dependence of disease on the relative proportions of the pores and of the circulating fluids; and in that of Themison, who regarded all diseases as depending on a lax or a strict condition of the solids of the body.

3. That the primary agents in the production of morbid phenomena are those peculiar vital powers different from the physical and chemical properties of inorganic matter, with which the living animal economy is endowed; sensibility, irritability, and an influence supposed to be exercised by the nervous system over the organs by which the natural and vital functions are performed, which some have designated animal power, cerebral action, or energy of the brain, and others innervation or innervatory influence. Of this doctrine Hoffmann seems first to have opened up the leading principles. The researches of Haller and of Whytt, and the pathological speculations of Cullen and Bordeu, gave it a still farther extension; and in the hands of Brown it received, what it has in some medical schools retained, the form of an exclusive system.

4. That in addition to its known vital, and to its physical and chemical properties, there is implanted in the animal economy one great, superintending, independent power or principle which regulates all its actions both in the state of health and of disease. Such has been supposed to be the principle denominated nature or innate heat by Hippocrates; pneuma, or spirit, by Athenaeus and the other members of the Pneumatic school; archeus, by Paracelsus and Van Helmont; and vital principle by Mr. Hunter in this country, by M. Barthez in the school of Montpellier, and by their respective followers.

It is not easy to say whether we ought to include under the last of these assumptions the animistic doctrine of Stahl, or to consider it as resting upon a separate and fifth assumption, viz., that the phenomena of the human economy, in the state both of health and of disease, are under the immediate government or control of the soul. When the term soul is employed as synonymous with the rational mind, as it seems to be by Stahl, the animistic doctrine must obviously be considered as distinct from all the other assumptions; but when the soul is spoken of as governing the functions of the body without the exercise of reason, the doctrine seems to ally itself with the principles mentioned under our fourth proposition.

Respecting the different theories of disease, it may be remarked, that each of them has varied in its outline and details at different periods, according to the general state of knowledge and the prevailing system of philosophy. It must be kept in recollection, also, that whilst in some systems one of the assumptions above enumerated serves as the sole basis or foundation of the doctrine, in other systems two or more of them are combined. Thus Hippocrates united in his system the doctrine of nature or innate heat with that of the four humours; Athenaeus that of the four elements with the pneuma; Paracelsus that of the body being composed of salt, sulphur, and mercury, with the doctrine of the archeus; and Hoffmann the influence of the nervous system, with the doctrines of the iatromathematicians. "In reviewing," says Buffalini, "the different theories or systems of pathology that have successively prevailed during the long period that has elapsed from the age of Hippocrates to our own time, we cannot fail to be struck by two circumstances; the first, that almost the whole of these systems are founded not on observations relative to the animal economy, but for the most part on the prevailing doctrines of the schools of philosophy; the second, that all of them (perhaps without exception) have had their origin in a very small number of fundamental errors, which, from being differently clothed and adorned, give the appearance of great variety, where in fact there exists a great similarity, of opinions."

The ancient systems of medicine are now very generally regarded as being so many attempts, founded on very partial and often erroneous observation, to reduce the whole physiological and pathological phenomena of the economy to a few primary principles; a simplification which it is hopeless to expect to attain, at least till these phenomena are much better understood separately, and in their relations to one another, than can for a long period be expected. The more correct views that at present prevail respecting the peculiar properties of animal bodies, for which medical science is so much indebted to the labours of Haller; and the extended knowledge that has been obtained respecting the morbid changes liable to occur in the physical and chemical conditions of the solids and fluids of the body, have certainly tended much to introduce a greater degree of precision than was formerly judged necessary, into the notions which pathologists entertain relative to the proximate causes of diseases.

It is in an order of advancement such as we have endeavoured now to trace, as having necessarily been followed by the early cultivators of medicine in regard to the deviations of the economy from its healthy condition; that is, in advancing from the consideration of individual cases to that of particular diseases, and from these, again, to general views of disease, that those must proceed who seek to improve the science of pathology. But where the object is to convey to others the results of the acquisitions that have already been made in the knowledge of disease, the order that may be most advantageously pursued is directly the reverse of this. Our view of diseases should commence with explaining the general principles that have been established respecting morbid structure and morbid function, considering each change of structure or function as constituting in itself a specific object of investigation, in all its possible effects, and in all its possible modes of production. It is in this way that we should be prepared to enter on the consideration of those combinations of symptoms which constitute or rather which mark particular diseases; to view each disease in respect of the course which it runs, the symptoms which it exhibits in its successive stages, and by which it is characterised and distinguished from other particular diseases; the nature and seat of the morbid actions, and of the morbid alterations of structure from which it may arise, or which it is liable to produce; and the circumstances which indicate a favourable or unfavourable termination to it. With a knowledge of particular diseases, in these various relations, such as is to be acquired from books and from lectures, the student is prepared for being conducted by an experienced practitioner to the bedside of the sick, and for having his attention directed to the phenomena of diseases as they present themselves in individual cases.

From this sketch, slight and imperfect as it has been, it is apparent that the consideration of the economy in its divided states, or the department of pathology, presents itself pathology, to the cultivator of medical science under three general aspects: 1st, that of the general doctrines of morbid structure and function, or general pathology, a branch of medical science which, though too long kept in the back-ground in the medical schools of this country, in consequence of its having been associated, in the courses of instruction, with other very interesting and very extensive departments, is now beginning to vindicate its due share of attention; 2d, that of the history of particular diseases, nosography or special pathology; and, 3d, that of the examination of individual cases of disease, or clinical medicine. And whilst the business of the teacher commences where that of the original investigator terminates, in the consideration of general principles, it terminates where that of the original investigator commences, in the investigation of individual cases of disease. Besides an acquaintance with the human economy in its healthy and in its morbid conditions, we have said that the science of Medicine includes an acquaintance with Morbific causes and Remedial powers. The advancement of medical men in the knowledge of these two classes of agents, and their modes of considering them respectively, must have kept pace with their progress in the investigation of diseases.

1. Whilst the attention of the pathologist was confined to the examination of individual cases of disease, he would naturally be led to inquire into the morbific agents, single or combined, by the operation of which each individual case had been produced; and in like manner, in combining groups of similar cases under general denominations, so as to establish particular diseases, it would be noticed that each disease, beside corresponding in the phenomena which it presented to the observer, in the different individuals in whom it occurred, also corresponded very generally in respect of the cause or causes by which it had been excited. On further investigation, however, it would be found that different diseases may arise from the same cause, as that rheumatism and pleurisy may both be produced by the operation of cold; and that different causes may produce the same disease, as that intense heat and intense cold may equally excite inflammation and gangrene. Medical men would then naturally be prompted to inquire what are the circumstances of correspondence and difference among the different causes of disease upon which it depends, that in their operation on the economy, similarity or identity of effect may arise from diversity of cause, or diversity of effect from similarity or identity of cause; and a foundation would thus be laid for the consideration of morbific causes, or what is usually termed Etiology, as a general doctrine in medical science.

It is the province of etiology, therefore, to ascertain what are the various powers that are capable of exercising an injurious influence on the human economy; to arrange these powers according to the most commodious classifications; to inquire into the channels through which those of them that are exterior to the body find their way into it; to ascertain upon what part of the constitution each of them primarily acts; and what is the nature of the change or changes in the economy, organic or functional, to which each of them gives rise. The study of etiology presents, indeed, a very wide field of investigation; for there is scarcely any agency in nature, material or mental (not excluding even those agents by which, under ordinary circumstances, the economy is maintained in a state of health, and those by which it is restored from a morbid to a healthy condition) that may not, under some circumstances or other, contribute directly or indirectly, immediately or more remotely, to induce the state of disease.

Independently of the material morbific agencies, physical, chemical, and vital, by which the human body is surrounded, and of the injurious influence which mental emotions may exercise upon it, there are frequently inherent in its own constitution, conditions that exert very important influences in the production of diseases and in the determination of their characters; conditions which, as marking deviations from the healthy standard, might be in some degree regarded as proximate causes of disease, but which, from the deviations being too slight to manifest themselves by any symptoms sufficiently characteristic of their existence, pathologists are wont to consider not as actual states of disease, but only as predispositions to disease. It is to this head of predispositions that medical men refer the diversities of temperament, constitution, or diathesis which different individuals exhibit, and which appear in some instances to be born with them, and in others to be acquired in the progress of life.

As the pathologist regards the symptoms of diseases as the consequences or effects of deranged conditions of certain portions of the economy, so he regards those morbid conditions in their turn, as the consequences or the effects of the operation of morbific agencies; and as the term proximate causes is employed to designate the morbid conditions, structural or functional, which give rise to the symptoms of diseases, so the term remote causes is used to denote the agencies by which these morbid conditions or proximate causes are themselves produced. The agency of the remote in exciting the proximate causes of diseases, must ever be a leading object of investigation to the scientific physician; since it is obvious that his power of arriving, in particular instances, at a knowledge of the proximate cause of a disease, must be materially aided, if, in addition to the judgment which he forms as to its nature from a consideration of the existing symptoms, he can also form a judgment upon this subject from a consideration of the causes by which it has been induced. Thus, for example, an acquaintance with the various effects which mental emotions are liable to induce in the economy, frequently enables the medical practitioner, (as in the case of affections of the heart), to correct the judgments which, from a consideration of the symptoms alone, he would be disposed to form of the nature of the diseases with which his patients are afflicted.

The extent of the difficulties that are experienced in endeavouring to trace the influence of morbificagents in inducing disease, may be inferred from the many points which, as is well known even to unprofessional persons, are still matters of doubt and controversy, relative to the origin or production, and to the diffusion or propagation of those two morbific powers which have been denominated specific, viz. terrestrial miasm or malaria, and human contagion. That an acquaintance with the laws which regulate the operation of the other agencies or influences that induce disease (the general or common morbific causes) must be still more difficult of attainment, may reasonably be presumed; since, whilst each of the specific agents uniformly produces, whenever its operates, one determinate or specific form of disease, each of the common exciting causes, on the contrary, may produce various forms of disease, according to the degrees and combinations in which it is applied to the human economy, and according to the particular circumstances in which the economy may at the time exist.

The term Hygiene has long been used as synonymous with Hygiène, the art of preserving health, to designate the consideration of the means which ought to be employed for maintaining the economy in a sound condition. It was justly remarked by Dr. Cullen, however, that there is truly no other means of preserving health, but what consists in the prevention of diseases; and that this again can be effected only by the avoidance of their exciting, or by the correction of their predisposing causes. Etiology, as treating of the sources of the exciting causes of diseases, and of their modes of action, is the necessary foundation of that part of hygiène which relates to their avoidance; whilst the correction of predispositions is really and truly, as Dr. Cullen observed, the removal of diseases; and the means of accomplishing it are no other than the remedies we employ in curing diseases, so that they may with propriety be comprehended under the title of therapeutics.

It is on the consideration of morbific agencies, as acting Medical upon large masses of men, that Medical Statistics are founded; this branch of investigation having for its principal object to ascertain the influence which peculiarities of climate, of diet, of occupation, &c., exercise on the populousness of different regions; on the liability of mankind to disease; on the characters of the maladies to which they are subject; and on the age to which they attain. To a country like this, holding such extensive colonial possessions in very different quarters of the globe, and having its own population engaged in so many kinds of employment, civil and military, agricultural, manufacturing, commercial, and maritime, medical-statistical inquiries are both interesting and important. 2. In considering the action of Remedial powers, the attention of medical men, it may be supposed, would first be directed to the effects produced by particular remedies in individual cases of disease. When they had advanced to the recognition of particular diseases, they would be encouraged to make use of those remedies which had proved beneficial in one case, in the treatment of other cases of what they regarded as the same disease; and lastly, when they had formed some notions of the internal morbid conditions, or proximate causes, on which different diseases depend, they would extend the employment of those remedies which seemed to have assisted in removing a particular proximate cause in one disease, to all diseases in which there seemed reason to suspect the existence of similar pathological conditions.

The measures which are in use for the prevention, cure, or alleviation of diseases, may be referred to three heads: First, those which relate to the management or regulation of those circumstances that are included under the head of regimen, such as the diet of the sick, the temperature and other qualities of the atmosphere in which they live, their clothing, and their exercise, bodily and mental,—comprehending, obviously, what used, in the language of the schools, to be called the non-naturals; second, the various operations requiring manual skill or dexterity, which it is necessary to perform for the relief either of internal or external diseases, such as the application of bandages, the operation of blood-letting, &c.; and, third, those substances which by experience have been found, when introduced into the system, to exert some influence on the economy that tends to restore it from some one of its diseased states to a healthy condition; as, for example, those substances which remove spasm and allay pain, (anti-spasmodic and narcotic medicines, as they are termed), and those which increase the alvine or the urinary evacuations, either when the action of the organs by which these evacuations are effected is deficient, and it is desired to restore them to their natural vigour, or when it is wished to increase their activity beyond its ordinary degree, laxative or purgative, and diuretic medicines.

An acquaintance with the substances which exercise beneficial influences on the diseased economy is obviously of essential necessity to the practitioner of physic. Of these substances some are derived from the vegetable, others from the mineral, and a few from the animal kingdom; and hence arises, in part at least, the importance to the medical practitioner of being acquainted with the sciences which treat of these several departments of natural history. But whilst some medicinal substances are employed as they exist in nature, or after undergoing some slight and unimportant manipulation, others can be obtained only by long and elaborate processes, many of them involving a knowledge of the principles of chemical science; and here again we see, in part at least, the cause why chemistry, since its earliest dawns, has been regarded as essentially allied to medical science. "Every substance," as was observed by the late Dr. A. Duncan, jun., "employed in the cure of diseases, whether in its natural state, or after having undergone various preparations, belongs to the materia medica, in the extended acceptation of the words. But in most pharmacopoeias the materia medica is confined to simples, and to those preparations which are seldom prepared by the apothecary himself, but commonly purchased by him as articles of commerce, from druggists and chemical manufacturers." It is the province of Pharmacy to consider the preparation which medicinal substances require in order to fit them for the purposes of the medical practitioner; whether these changes shall be of a mechanical or chemical nature; whilst the consideration of the effects which medicines and other remedies are capable of producing on the different systems and organs of the economy, constitutes that department of medical science usually denominated general Therapeutics. All these various kinds of knowledge relative to medicines, their natural history, their pharmaceutical preparation, and their therapeutical powers, it has been by some proposed to include under the general title of Pharmacology.

The improvements that have been made, or that remain sources of improvement, in the department of materia medica, may consist either in making additions to, or subtractions from, the number of substances employed for medical purposes. Additions may be made to the number of medicines either from the discovery in substances already known, of powers or virtues which they were not known to possess, or from the discovery of entirely new substances possessing therapeutic powers. The baneful influence of spurred rye in producing gangrene has been long known, but it is only of late that attention has been particularly called to the power which that substance is by some alleged to possess of exciting the contraction of the muscular fibres of the uterus. The noxious influence of the different acetates of lead, when internally administered, has likewise been long known, and particularly their effect in exciting colicky pains, but it is only of late only that their influence in suppressing excessive intestinal evacuations, and in restraining haemorrhages, has particularly attracted the attention of medical men. Iodine, on the other hand, may be mentioned as an instance of a substance which within a short time after its discovery, acquired a high character in the estimation of many practitioners, for its therapeutical virtues. The history of the croton oil, the powerful action of which upon the intestinal canal is now familiar to every one, affords a remarkable example of a medicine the knowledge of the powers of which has been very slowly diffused among medical practitioners. It would appear that the seeds of the croton tiglium have been in use among the natives of the East from time immemorial, and that they were formerly known in Europe as a drastic purgative, under the name of grana molucca or grana tiglii. They had fallen, however, into oblivion, when the attention of the profession was again called to them by the observations in Sir White-law Ainslie's Materia Medica of Hindostan, that gentleman having been induced to point out this medicine to the particular notice of the medical men of India, from finding that it was highly prized by the Hindoo doctors, and extolled in various satirisms or professional tracts. It appears, moreover, that the oil, in which the purgative virtue resides, was first prepared and used in medicine by the Dutch surgeons in India, about a century ago, a single drop taken in Canary wine being employed as a common purgative. It is only, however, within these few years that the use of the croton oil has been introduced into Europe.

The difficulty that is experienced in arriving at a sound judgment with regard to the medicinal powers of the remedies which every now and then are obtruded on public notice, with lofty and but too often exaggerated panegyrics, renders it very necessary to rid the pharmacopoeia from time to time of inert and useless substances. The expulsion from our pharmacopoeias of a great many substances of this description within the last century, and the much greater degree of reserve with which new substances are admitted into them, than was formerly practised, afford a gratifying proof of the steady advancement of correct discrimination in this department of medical science.

The progress which has recently been made in chemical knowledge has contributed very materially to improve the department of pharmacy. This improvement is particularly conspicuous in the preparation of vegetable medicinal substances. The employment of steam instead of fire in the preparation of vegetable extracts, presents an elegant though simple illustration of a pharmaceutical process improved upon chemical principles. The separation from many vegetable substances of the principles on which their medicinal virtues depend, so as to allow of these being administered free from a quantity of useless and possibly hurtful matter, (as the separation, for example, of quinine from bark), affords Remedies, an illustration of a still more elaborate and not less important application of chemistry to pharmaceutical science.

If it be reasonable to expect that medical men are to be aided in the treatment of diseases by an improved knowledge of their nature, therapeutics cannot fail to derive benefit from every advancement that is made in pathological science, and particularly in the knowledge of the proximate causes of diseases. But the action of remedies in restoring health is so dependent upon, and so mixed up with, the natural or spontaneous operations of the economy, as to render it at all times a matter of the utmost difficulty, for the most careful and candid observer, to determine or even conjecture what part of the result is attributable to the one, and what to the other of these joint influences. It must be confessed, indeed, that we are still far from knowing what nature accomplishes in different diseases by her own unassisted efforts towards the restoration of the diseased body to a sound or healthy condition; what she accomplishes when judiciously assisted by medical art; and what she does not effect either singly or with all the aid that medicine is able to render her. These are the great problems in therapeutics, for the solution of which it must be the main object of scientific practitioners to furnish the necessary materials. There can be no doubt that morbid anatomy, by the light which it has thrown upon the proximate causes of diseases, has contributed very much to correct and extend the views of medical men as to what is curable and what is incurable in disease, as well as to guide them in forming their therapeutical indications. Thus, it may be remarked, that to the success of medical practice, nothing is more important than the power of discriminating when a stimulant or repleteing, and when an antiphlogistic or depleting mode of treatment ought to be pursued. The knowledge that has been obtained, by means of dissections, of the circumstances under which inflammatory affections are liable to develop themselves in the different organs and textures of the body, in the progress of various diseases in which their occurrence is apt to be overlooked, has been of great use in assisting medical men to discriminate the cases in which these two plans of treatment are respectively to be preferred.

In reference to the progress and present state of therapeutical science, it deserves to be noticed, that in proportion as medical men have become better acquainted with the operations of the economy in its healthy and morbid conditions, the number of medicinal agents reputed to be possessed of specific therapeutical powers, that is, to be capable of exercising a beneficial influence in curing particular diseases, without any external manifestation of their immediate mode of operation, on which their beneficial influence may be supposed to depend, has gradually diminished. This may be attributed, perhaps, in part to medical men having been able to ascertain the particular actions which these supposed specific medicines exert upon the economy; and partly to their being less credulous in admitting the efficacy of remedies, of whose mode of operation they are unable to form any conception.

Such is a slight view of the three departments into which we have said that medical science admits of being divided;—that which considers the human economy in the state of health; that which considers the same economy as affected with disease, and that which investigates the powers or agents by which health may be banished and disease produced, or on the other hand, disease dispelled and health restored. But besides those branches of knowledge that are to be regarded as more strictly medical, there are others, an acquaintance with the principles of which is most important or even essential to the cultivator of scientific Medicine. It is to these that the well-known observation of Celsus is applicable, "Quanquam multa sint ad ipsam artem proprie non pertinentia, tamen eam adjuvant, excitando artificis ingenium;" itaque ista quoque naturae rerum contemplatio, quamvis non faciat medicum, aptorem tamen medicinae reddit." Amongst the sciences auxiliary or accessory to medicine may be justly reckoned natural or mechanical philosophy, chemistry, and natural history.

A knowledge of mechanical philosophy is indispensable to Medical men; a right understanding of the actions of several of the organs of the body in the state of health, and consequently of surgery; as well as of the deviations from the healthy state to which these organs are liable in disease; and this knowledge is necessary also to the right comprehension of the action of several external agents upon the body, both in the state of health and of disease.

Though the higher phenomena of the human body arise from its being endowed like the bodies of other animals with peculiar vital properties, and from its being associated with a rational mind, yet it must still be regarded as a piece of mechanism of the nicest and most elaborate construction; and it is impossible to arrive at correct or enlarged notions with regard to its structure without possessing an adequate knowledge of the principles of mechanics. Hence it is, indeed, that the language of anatomy is replete with terms derived from mechanical science. The study of animal mechanics, or what may be termed structural physiology, that is, the consideration of the mechanical contrivances discoverable in the construction of the different parts of the body, a branch which furnishes so ample a field of illustration to the student of natural theology, essentially requires to be combined with the study of anatomy; since without it the latter would be only a dull and uninteresting record of names, forms and dimensions. Thus, for example, to give an interest to the study of that extensive portion of the animal frame which is subservient to voluntary motion, it is essential that each muscle, bone and joint should be considered in its mechanical relations; and nothing certainly can be more calculated to excite admiration than, in contemplating the arrangements of these parts in reference to the properties of the lever, as constituting respectively the moving power, the resistance and the fulcrum, to become sensible of the advantages that are obtained in respect of elegance of form and rapidity of movement, by the sacrifice of a portion of that force with which the muscular fibres have been so largely endowed.

It would be easy to adduce many illustrations to show how essential a knowledge of mechanical principles is to the comprehension of the vital and natural functions of the animal economy. The inquiry as to what the powers are by which the blood is moved through the body, is one which cannot be properly prosecuted without an acquaintance with the laws of hydraulics. It is to the too frequent ignorance on the part of physiologists, of the principles of mechanical science, that must be attributed much of the doubt which still prevails on many points relative to the function of circulation, and, particularly as to whether the motion of the blood depends wholly upon the propelling powers of the organs within which it is immediately contained, or with which these are themselves surrounded; or whether it be not partly attributable to the pressure of the atmospheric air over the whole surface of the body, acting in co-operation with the production of a vacuum at the central organ of circulation. From finding themselves unable to refer all the various motions that are observed to occur in the solid and fluid parts of animal bodies, to the known properties of inorganic matter or of organic structure, some physiologists have been led to imagine that there exists in these bodies a secret or unknown principle capable of giving rise to various physical motions, as well as of producing other phenomena, in the economy; and to this principle they have given the name of the vital power. It seems reasonable, however, to hope that in proportion as we shall obtain a more precise knowledge of the motions that actually occur in animal bodies, and of the principles or Accessory sources of motion that are in operation throughout organized and unorganized nature, the occasion will cease for employing this ambiguous and unconstructive term. It is proper indeed to keep in mind that within no very great length of time, several different kinds of motions occurring in organic bodies have been brought to light, which probably exercise considerable influence on the functions of organized beings. To these may be referred the motions performed by extremely minute particles of solid matter, whether obtained from organic or inorganic substances, when suspended in pure water or in some other aqueous fluids; and which from their irregularity and seeming independence, resemble in a remarkable degree the less rapid motions of some of the simplest animalcules of infusions. We have another example of a recently discovered principle of motion in endosmosis and exosmosis, or that power or property in virtue of which there takes place a reciprocal transmission through all organic membranes and some inorganic laminae, of fluids which are in contact with their opposite surfaces, and which differ from one another in certain physical conditions. An analogous principle of motion has also been found to operate in the case of gases and to regulate their diffusion. It would be out of place to inquire here what particular phenomena in the animal economy have received, or may receive, elucidation from these or other sources of physical motion of which we have recently arrived at the knowledge. But it is obvious, that besides these, there may be yet undiscovered sources of physical motion, operating in the production of those phenomena in the economy of living beings, which physiologists, from not being able to refer them to any of the known sources of motion, have been wont to regard as the effects of a peculiar vital principle.

There are many problems in pathology also, for the solution of which it is absolutely necessary to appeal to the principles of mechanical science. Thus it has been of late only that pathologists have sufficiently turned their attention to the physical considerations which it is necessary to keep in view in any explanation that may be attempted of the conditions of the encephalon, (that is, of the brain and the solids and fluids connected with it,) upon which the production of coma or insensibility depends, viz., first, the unyielding nature of the cranium, or bony case of the encephalon; second, the exemption of the encephalon, so long as its bony case remains entire, from the pressure of the atmosphere, except in one direction, the aperture at the base of the skull, through which the spinal marrow passes; and third, the impossibility of the entire encephalon or any of its parts, undergoing a sensible degree of compression from any force to which they can be subjected during the continuance of life. Again, in surgical pathology, we have an illustration of the benefits to be derived from a knowledge of mechanical principles, in the light which they have thrown upon the variations in the effects produced by penetrating wounds of the chest, according to the proportion between the size of the wound and of the aperture of the glottis; and according as the substance of the lungs has or has not itself been injured, so as to allow of air passing from the respiratory cells into the cavity of the pleura. Those who require more immediate illustrations of the applicability of mechanical science, to practical purposes in the removal of disease, may find many such in the contrivance and application of surgical instruments and apparatus. The advantages to be derived in many diseases from the observance of the horizontal posture, and from bandaging, simple as these means appear, would probably be more duly appreciated than they are, were medical men more in the habit of considering the physical influences to which the body is subjected.

Chemistry. Of the applicability of chemistry to the several branches of medical science, notice has been taken in speaking of each of these branches successively. We need not repeat how important an acquaintance with chemistry is to the practitioner of pharmacy. The anatomist derives assistance from chemistry in the prosecution of his researches. The physiologist finds that many of the phenomena occurring in the animal economy depend on processes of combination and decomposition; and are as strictly of a chemical nature as any which are conducted in the laboratory of the chemist on unorganized substances. The pathologist has learned that from various circumstances these chemical processes are liable to be deranged, so that the products are different from what they should be; and the therapist has hence been led to enquire what are the appropriate remedies by the administration of which the natural composition of the products may be restored. From the light which has been already derived from this branch of science, since it was first applied to the investigation of the phenomena of the animal economy in health and disease, we are warranted in anticipating that it will still powerfully contribute to elucidate many points in medicine which are at present involved in obscurity. "The imperfection of pathological chemistry," says M. Prunelle, "obliges us to refer to the vital forces, a host of diseases which necessarily depend on lesions of mixture. A great number of physiological and pathological phenomena which we consider at present as dependent upon the vital forces, will pass under the domain of the chemical and the organic forces, in proportion as the laws of these forces shall be better known and more generalised."

With regard to the applicability of a knowledge of natural history to purposes of medical science, it may be remarked, that whether we consider the human economy in the state of health or of disease, or turn our attention to the operation which morbific or therapeutic agents exert upon it; in each department important aid may be derived from an acquaintance with the three kingdoms of nature.

How much assistance we receive in attaining an accurate knowledge of the structure and functions of the human body, from tracing through the successive series of animals, the instruments that are subservient to their several functions, and the manner in which these functions are exercised, there has already been occasion to remark. It seems reasonable to expect, that as the study of the lower animals has contributed to improve our knowledge of the anatomy and physiology of man, so, in like manner, much benefit should accrue to pathology from similar comparative investigations. Morbid anatomy, for example, ought certainly to be prosecuted to much advantage in the inferior animals, not only from the parts being, in some cases at least, upon a larger scale, but from our having an opportunity, by putting the animals to death, to trace the effects which the action of different morbific causes produces upon the structure of their different textures and organs; as well as to examine the changes which diseases induce in the successive stages of their progress. The experiments and observations that have been made with regard to the development and progress of cysts and tubercles in the lungs and other organs of some of the lower animals, besides suggesting some interesting views respecting the series of changes that occur in morbid structures, have given rise to important considerations respecting the circumstances under which these morbid changes of structure are most liable to take place. The liability of animals kept in confinement to undergo diseases from which they are exempt, or to which they are less subject in their natural condition, suggests another hint that may prove serviceable in the study of morbific causes. A very direct source of interest in veterinary medicine arises to the physician, from the fact that some of the diseases depending on specific contagions, to which the lower animals are liable, are capable of being communicated to the human subject. It is to the observation of a fact of this kind that we are indebted for that most invaluable discovery, the protection against small-pox afforded by having Accessory passed through a disease which, whatever may be its primary source, is best known as occurring upon the udder of the cow. The other diseases which are liable to be propagated from brute animals to the human species, such as hydrophobia, glanders, pustule maligne, &c., we know only by the injurious effects which they produce.

From the correspondence of many of the diseases of the lower animals with those of man, it seems obvious that animals may be made the subjects of therapeutical as well as of physiological and of pathological experiments. The use of the cautery, for example, particularly in diseases of the joints, has probably been advanced in surgical practice from the experience which veterinary surgeons have obtained of the beneficial effects of firing upon the horse.

It may be remarked too, that whilst a large portion of the animal kingdom is rendered subservient to mankind in the way of food, and a few animals supply remedial agents, there is a considerable number which produce, in various ways, noxious or poisonous effects upon the economy. Certain animals secrete, when in the state of health, noxious fluids which serve them as means of attack and of defence, on account of which power they are designated under the common name of venomous animals. These animals, of which the mammalia and birds do not present any species, are found principally among the serpents, insects, and zoophytes. It has been alleged that some fishes also are capable of communicating a venomous character to the wounds which they inflict with their pricks. But fishes and some species of mollusca are better known for their poisonous qualities when employed as articles of food. Of poisonous fishes, again, there are some which are essentially poisonous, that is to say, they are so at all times, although they are not distinguished by any anatomical character from those which are most salubrious; whilst other fishes which are in general more or less healthful and agreeable as articles of food, become hurtful only accidentally; whether their noxious character then depends, as some have supposed, upon the season, or, as others have imagined, upon their having made use of a particular kind of nourishment; or, as others again have conjectured, is attributable to a particular morbid state, and the consequent formation of a poison sui generis, that is diffused over the whole substance of the animal.

It is sufficiently obvious that for the acquisition and extension of this species of knowledge, and for the power of turning it to account in the different circumstances in which they may be placed, medical men must be dependent on an acquaintance with zoology.

The most important benefit, certainly, which medicine derives from the knowledge of the vegetable kingdom is in relation to the purposes of the materia medica, and to the investigation of poisons. Botany, however, is not without its use in the elucidation of the functions of the animal economy. In plants we have an opportunity of witnessing the performance of two classes of functions, those essential to the preservation of the individual, and those necessary for the continuance of the species, under the most simple conditions in which they can be executed. And, independently of any resemblances that might be traced in the functions of circulation and secretion as performed by plants and by animals, those which have been ascertained to exist between the chemical processes attendant upon germination and vegetation in plants and on respiration in animals, afford a very interesting analogy between the operations of these two classes of organised beings.

The benefits to be derived in scientific medicine, from the investigation of the inorganic kingdom of nature, are not less than those which result, as we have endeavoured to shew, from the study of the other two kingdoms. The connection between epidemic diseases and particular kinds of weather, whether as occurring regularly at particular periods of the year, or as varying in different years without any fixed rules, is a subject of medical consideration which may be expected to receive some light from the science of meteorology. The influence of climate upon the human economy, and particularly in the production, modification, and removal of diseases, confers a great share of importance on the investigation of all those circumstances upon which the character of a climate depends; the atmosphere, the soil, and the waters which flow from it, or with which it may be surrounded. A knowledge of the principles of meteorology and of geology is essential therefore to any correct views of Medical Topography.

The fascination exercised over many minds by those various branches of natural knowledge, which we have here represented as the auxiliary sciences of medicine, have led some to regard with much jealousy, invitations or recommendations to medical men to engage in their study. This jealousy, however, seems to arise from a total misconception as to the manner in which they ought to be prosecuted when considered as branches of a medical education. To acquire a knowledge of the details of any one of them is probably sufficient to occupy the time of a person of ordinary application; and would consequently be to most persons inconsistent with the prosecution of studies of a more strictly medical character. But without the sacrifice of any knowledge essential to his profession, a medical man may attain a competent acquaintance with the general principles of these auxiliary sciences sufficient to enable him to understand their bearings upon medicine. In possessing a knowledge of these principles, he holds an instrument in his hand by which he may be able to work out any part of the details of these sciences that may seem capable of throwing light upon any point of medical doctrine or practice to which his attention may happen to be particularly called. To the extent that we have hinted, therefore, a medical education cannot be considered as complete which does not comprehend an acquaintance with these several auxiliary sciences. "It is not possible," says an intelligent author, whose country is apparent from his illustrations, "that a medical man should know botany like De Jussieu or Richard; chemistry like Vauquelin, Thénard, and Bouillon La Grange; physics like Biot and Gay-Lussac; mineralogy like Haüy; and natural history like Cuvier and Dumeril: but a knowledge of the elements of these sciences is indispensable to him; and immense as is the domain of medicine alone, he may very well, if he chooses, find time to make some excursions on neighbouring territories."

In the exercise of Medicine as a practical art, the second Medicine point of view in which we have said it must be considered, as an art, three branches of the profession independently of pharmacy or the preparation of medicinal substances, have long been recognised: surgery, physic, and midwifery. To the domain of Surgery have been referred, besides injuries produced by agents operating on the external surface of the body, those diseases which, in addition to the ordinary means of cure, require the assistance of the hand, and are thence called surgical or surgical diseases; and to that of Physic, those diseases which may be cured, without the employment of manual operation. An attempt has been made to identify this division of diseases into surgical and medical, with those into local and constitutional, and into external and internal diseases. But it must always be remembered that the different textures, systems, and organs of which the human body is composed, are arranged so as to form an entire whole, the various parts of which act on, and are reciprocally acted on by one another. Although, therefore, some morbid affections occurring on particular parts of the external surface of the body, and consequently regarded as surgical, may produce no disturbance of the general economy, or attended with constitutional symptoms too slight for observation, yet there are external or local diseases which Practice, often produce constitutional effects of the most alarming and fatal nature. Symptomatic and hectic fever, locked-jaw, convulsions, and epilepsy, may be mentioned as some of the more remarkable constitutional affections which are produced by the action of local diseases. And on the other hand, internal and constitutional diseases, which are consequently regarded as falling under the province of the physician, occasionally become attended in their progress with external or local affections requiring surgical interference; as when abscesses occur in the progress of fever, or fistula in the progress of consumption; or when pleurisy terminates in empyema, or disease of the liver in ascites or edema. "It is in the knowledge of these and of similar diseases, that the boundaries which divide physic from surgery meet and are lost in each other; for whatever distinctions convenience or custom may have introduced among the practitioners of the healing art, there is no foundation for these distinctions either in the nature of diseases, or in the knowledge that every medical practitioner should possess of the appearances which different diseases exhibit, and of the means by which they are to be removed. Division of labour may, indeed, in medicine as in the other practical arts of life, be attended with many advantages to society; but in learning and in teaching the elements of physic and of surgery, it must never be forgotten that they are branches of the same art, have had the same origin, are governed by the same principles, and pursue entirely the same object." It is not, indeed, in the kind or in the extent of their knowledge, that the physician and surgeon of the present day are to be distinguished; but in the latter's being possessed of, and accustomed to exercise those powers of head and hand upon which the skilful performance of difficult or dangerous operations must depend.

No topic ever gave rise to more acrimonious controversies, than the question as to the necessity or expediency of physic and surgery being practised as separate and distinct professions; and, where such a separation has been made, as to the proper relation of the practitioners of these professions, to one another. But, whilst the practitioners have been engaged in discussing, the public has settled the matter on its own judgment, and in the manner best suited for its own convenience. Everything seems to intimate that at the present day there exists a strong disposition on the part of a large portion of the public, to entrust the charge of their health, and of that of their families, under whatever kind of malady they may suffer, to some one practitioner in particular; and in the event of there appearing obscurity, or reason for apprehension in the complaint, then to avail themselves of the additional advice or assistance of some person or persons supposed to have directed their attention in a particular degree to cases of a similar description. Accordingly, it is only in cities that are the residence or the resort of large numbers of people, that any medical men can attempt to confine their practice to the treatment of medical or surgical cases exclusively; and, even in such situations, the great bulk of practitioners must, like their brethren in smaller towns and rural districts, to a greater or less degree, combine the exercise of all branches of practice. It is by having sagaciously perceived, and judiciously availed themselves of this disposition on the part of the public, that the apothecaries of England have obtained so extensive and firm a footing in medical practice in that country.

Under the department of Midwifery, is included everything connected with the process of child-bearing, and the diseases to which women are subject, both during gestation and after parturition: and as the class of practitioners who occupy themselves especially with the practice of midwifery, are favourably circumstanced for becoming acquainted with those diseases peculiar to women, which are unconnected with child-bearing; as well as with the diseases of infants; it has become usual to include these diseases also in systematic views of this department of medical practice.

It is satisfactory to find that the medical corporations of this country have at last extended the right hand of fellowship to the practitioners of midwifery. Nothing, indeed, could be more ridiculous than the grounds upon which they have hitherto held its exercise to be a disqualification for corporate association. If there be any class of practitioners, of whom, more than another, it is desirable that to great practical skill, and to an extended acquaintance with all departments of medical science, they should unite the greatest delicacy of feeling, and refinement of manners, it certainly must be those engaged in this branch of the profession. It would be strange, therefore, if the public, for the gratification of some absurd notion of professional etiquette relative to manual operation, were to sanction with its approbation the affixing a stigma to a profession in which such qualifications are desirable.

In reference to medical practice considered as an object of legislative regulation, it may not be out of place to remark here, that there are two principal modes in which legislatures have endeavoured to improve the profession of medicine. The first of these has been by making arrangements for the conferring of distinctions upon persons, who, from the education they have received, and the examinations they have undergone, may be considered as competent to exercise the different branches of the art. The second mode, and that which it has hitherto been the great object of all plans of medical reform in this country to enforce, has been the suppression of unlicensed and incompetent practitioners, by penal enactments. That the pointing out the competent is a just and expedient interference on the part of the legislature, does not seem to admit of doubt. But the suppression of the incompetent seems not only questionable in respect of justice, but incapable of being enforced in a country politically constituted like this, so long as there exists a taste for quackery in the public mind. It is as regards the employer rather than the employed, that the justice of this interference may be doubted; for there seems no good reason why, if a person prefers the doctor of nature, as the quack is supposed to be, to the doctor of the schools, the legislature should control him in his choice. It has usually been pretended, indeed, that the object of such enactments has been the protection of the poor and the ignorant against the unskilful. But the exception generally made in favour of gratuitous practice, suggests a doubt whether those at whose instigation the legislature has sanctioned such enactments, may not have been influenced in demanding them by other less ostensible motives. Experience seems to have shown that the prosecution of quacks, particularly when this has been conducted at the instance of medical corporations, so far from suppressing has rather had a tendency to strengthen the public taste for quackery. The only mode in which it can be expected that this taste will be overcome, is by disseminating among the community sound views of health, disease, and remedies, so as to enable them to appreciate the pretensions of those who profess to accomplish things which it requires only a little information to know to be impossibilities. So long, however, as the taste shall continue to prevail, it is surely much better that it should find vent in the employment of professed quacks, than be directed to the corruption, we would say prostitution, of regular practitioners. The legitimate means by which unlicensed practitioners may be discouraged, by the legislature, are, first, their not being allowed to hold public appointments; second, their having no legal claim to remuneration; and, third, their being punished in case of their assuming a title which they have not legitimately acquired. Further than these measures, it is not to the legislature that the medical profession should look for assistance in suppressing quackery and quacks. It is impossible to allude to the interference of the legislature in matters relating to medical education and practice, without congratulating the medical profession and the public in general, on the very full inquiry recently instituted into these subjects under the authority of the House of Commons. The number of contending interests, real or supposed, requiring to be consulted, and the jealousy felt by some of the parties, of undue partialities being entertained in influential quarters, in favour of their competitors, rendered it proper to receive a mass of oral and written evidence of so great extent that some time has necessarily been consumed in its digestion. We venture to hope that the intelligent and indefatigable chairman of the committee, (to whose extraordinary perseverance in expediting information, and patience in receiving what was offered, we have much pleasure in hearing our humble testimony,) will ere long propose a system of medical legislation in which the principles shall be fully recognised, that whatever distinctions or divisions, political or medical, may formerly have existed, or there may still in some minds be the wish to maintain, the different branches of medicine form only one science, and the different parts of the British dominions only one empire.

In the intercourse of society, many questions arise which, though not bearing immediately on the treatment of diseases, are yet so connected with the consideration of the human economy in its healthy or diseased states, that the advice and opinions of medical men are very frequently required respecting them. Of these, some relate to the means of detecting crimes; others to the capability of individuals for discharging the social or civil functions of life; others to the means of preserving the public health, and so forth. It is the object of Medical Jurisprudence to explain at least the general principles by which medical men should be guided in forming their opinions on the particular points that may be referred to their decision. For the proper cultivation of this branch of study, there is no single department of medical science a knowledge of which is not necessary. Chemistry, materia medica and pharmacy, anatomy and physiology, surgery, physic and midwifery, must all contribute their several lights for the elucidation of many of those medico-legal questions on which the medical man is called to pronounce a judgment; and we have but too often reason to lament the deep and painful obscurity in which, notwithstanding all possible assistances, many of these questions are still left involved.

No branch of medical jurisprudence has made more rapid progress than that which relates to the power of detecting, by chemical reagents, the presence of poisonous substances, not only in the various media in which they may be administered, but also subsequently to their introduction into the body, and their diffusion through its different fluid and solid parts. But whilst toxicology, or the consideration of poisons, has been thus greatly advanced by the improvement and extension of chemical knowledge, it has likewise received most important contributions from branches more strictly medical. The symptoms to which poisons give rise during life, and the changes which they produce upon the surfaces with which they come immediately in contact, as well as on more remote organs, and which are discoverable after death, have been investigated with great attention, with a view to their discrimination from similar symptoms and changes occurring as consequences of disease.

Morbid anatomy has rendered important services to medical jurisprudence by directing attention to those appearances in the different textures and organs of the body, which are the consequences of changes occurring subsequently to death or immediately previously to it; and by teaching medical men to distinguish these pseudo-morbid appearances from those that are the genuine products of disease, or of injury inflicted during life.

To surgery medical jurisprudence looks for a determination as to the amount of external violence of different kinds by which death may be occasioned; and particularly for ascertaining the circumstances upon which it may depend, that injuries apparently trivial in their degree may give rise to most injurious or even fatal consequences. It is the province of the surgeon also to endeavour to judge, in cases of injury depending on external violence, as to the nature of the means or instrument by which the injury had been produced.

The medico-legal questions which fall more particularly under the consideration of those who are engaged in the practice of midwifery, are many of them of an extremely delicate nature in a moral point of view, and extremely difficult of determination. As illustrations of these may be mentioned the questions as to the variations in the length of time during which gestation may continue in the human species; as to the earliest period of its uterine existence at which a human fetus can live, when separated from its mother naturally or by artificial means; and as to the marks by which it can be determined whether an infant found dead, had or had not survived the period of its birth.

No class of medico-legal questions proves more frequently perplexing than those in which it is necessary to pronounce a judgment on the mental sanity or insanity of an individual; to determine whether he labours under such a degree of mental weakness or aberration, as to be incapable of managing his own affairs, or unfit to be trusted with the control of his own actions, or as to render some restraint upon his proceedings proper or necessary for the safety of others. The difficulties in cases of this kind are most materially increased by the circumstance that the mental aberration may implicate only one small portion of the intellect, the individual speaking and acting rationally except in so far as he may be misled by a single hallucination; and they are greatly augmented also by the circumstance, that persons thus insane upon particular topics, not unfrequently possess the power, when suspicious of being objects of attention, of concealing the particular delusion under which they labour.

So far as medical jurisprudence bears on the preservation of the public health, it must, like hygiene, of which, indeed, when viewed in this light, it forms a part, be dependent on the study of etiology. The circumstances under which human contagions or terrestrial miasmata are engendered; the laws according to which their diffusion is regulated, and the means best suited for preventing their propagation; the influence which other effluvia exert upon the economy, as, for example, those produced in the operations of manufactories of different kinds; the circumstances under which particular provisions become unwholesome or poisonous;—these and many other etiological questions, medical men are constantly liable to have referred to them by the public authorities, either with a view to the adjustment of private rights, or to the preservation of the health of communities.

The whole range of Medicine, it thus appears, may be divided into two parts; the scientific or theoretical, and the empiric or practical. The theoretical part again naturally divides itself, so far as regards the study of the human economy, into four branches: 1st, a knowledge of the structure of the body in the state of health, or Anatomy; 2d, a knowledge of the functions of the economy in the state of health, or Physiology; 3d, a knowledge of all that relates to diseased structure and diseased function, or General Pathology; and, 4th, a knowledge of the powers of remedies, or General Therapeutics. The practical part of medicine may also be marked out into four divisions: the 1st, comprehending Surgery, or the consideration of external diseases and injuries; the 2d, Physic, or the consideration of internal diseases; the 3d, the principles of Midwifery; and