his essay on the skin and lungs.

"it is madness and a contradiction to expect that things which were never yet performed should be effected, except by means hitherto untried."—bacon, nov. org. aph. 6.

when we consider the object which the distinguished author had in view, in the immortal work whence we have taken the foregoing simple but instructive aphorism, we cannot but perceive how highly suggestive it is to those engaged in scientific researches, or how necessary to be borne in mind by those who are really aware of the present state of medicine and surgery, and desirous of seeing them become a definite science. nor does it appear inappropriate to the consideration of abernethy's experimental inquiries into the functions of the skin and lungs. an extended investigation—of which his paper on these subjects contains an excellent type, and is in part a practical application—would be a great step towards the creation of a real science, and would certainly fall within the "means untried" of lord bacon.

although the latter part of the last century, and the first half of the present, have been very remarkable for the number of distinguished men who have flourished during that period, in almost every branch of knowledge; yet neither the bar nor the senate, neither literature nor any of the sciences, can boast of greater men, nor lay claim to more positive improvement, than chemistry.

if we only consider that interval between the discovery of oxygen by priestley, in 1774, and the conclusion of sir humphrey davy's labours, chemistry almost seems like a new science; and it continues to advance with such rapidity, and is daily opening62 out so many new questions, that the most accomplished chemist of one year is never sure how much he may have to learn the next; nor, unless he reasons with great caution, how much he may have to unlearn.

to a physiologist, who requires assistance from all branches of science, chemistry must always be an interesting study. when we lay aside all speculations as to what is the abstract nature of life, and study that which is the proper object of philosophy—that to which it seems the faculties of man are limited—namely, the laws in obedience to which the phenomena in nature occur; and apply the knowledge thus obtained to the occurrences which take place in the human body; we soon discover that, whatever the abstraction "life" may be, we live proximately, in virtue of certain changes in various forms of matter; as food, air, the various constituents of our bodies, &c.; and that these consist of multiplied separations and rearrangements of their respective elements, which it is the special province of chemistry to examine.

if we investigate the changes of the living, or the structure of the dead, with these objects,—we shall be in no danger of perverting chemistry to purposes to which it is inapplicable. when, however, we proceed a step further, and seek to give a chemical expression to various uses and relations of different parts of the body, the greatest caution is required.

in the first place, in a machinery which is a practical application of a great many sciences, it is to the last degree improbable that they can be expressed by any one.

again, to estimate the true meaning—the physiological interpretation of many changes which might be in their proximate sense chemical,—a greater familiarity with the phenomena of disease is necessary than usually falls within the inquiries of the most scientific chemist.

to a person acquainted only with the ordinary phenomena of health, or who is not even something also of a philosophical pathologist, chemistry is for ever suggesting tempting analogies, which are constantly tending to mislead him to conclusions on insufficient data; and to examine and rest too much on the chemical facts deducible from one or other function, without sufficiently63 attending to the physiological relations of that function with all others.

in fact, for want of due caution, or it may be of a sufficient range of information, the assistance which chemistry has hitherto rendered to physiology has been attended with so many assumptions, that it is extremely difficult to say on which side the balance lies—of advantage or error. we are aware that at this moment there is a contrary feeling—a kind of furore for chemical solutions of physiological phenomena. we believe the caution we venture on suggesting was never more necessary.

the discovery of oxygen gas by priestley, not only gave a great impetus to chemical inquiries, but affected physiology in a very remarkable manner; when it was found that the more obvious phenomena of all cases of ordinary burning—lamps, candles, and fires of every kind—consisted mainly of the chemical union of charcoal and oxygen (carbonic acid); and again, when it was discovered that animals, in breathing, somehow or other produced a similar change, one may conceive how ready every one was to cry, "i have found it. the heat of animals is nothing more than combustion! we inhale oxygen; we breathe out carbonic acid; the thing is plain. this is the cause of animal heat!"

it has always struck us as a curious thing that chemists should have attached such a dominant influence, in the production of heat in animals, to the union of carbon and oxygen; because nobody is necessarily so familiar as they are with the fact that the evolution of heat is not at all peculiar to the union of these bodies, but is a circumstance common to all changes of every kind, in all forms of matter—there always being either the absorption or the evolution of heat.

there is no doubt that the analogy is very striking between the changes which appear to be wrought in respiration, and those which take place in ordinary combustion. a very little consideration, however, shows that the idea that respiration is the cause of animal heat, or that it is due to any other change of oxygen merely, is not only an assumption, but in the highest degree doubtful. in the first place, the carbonic acid thrown out when we expire, is certainly not made by the immediate union of the64 oxygen inspired with the charcoal expired; secondly, nothing is so obvious that in respiration there is an immense quantity of heat thrown out of the body. but as it is very desirable that the subject of this paper of abernethy's on the skin and lungs should be understood, we will give the reader a simple view of the nature of these important organs; and as one (functionally considered) is as much a breathing organ as the other, we will say a few words first of the lungs.

in all animals19, the blood, or other fluid in which the elements of nutrition are sent to all parts, is exposed to the action of the air; and this is what we call breathing or respiration; and the exposing of the blood to air is so arranged that both fluids are in more or less rapid motion. the staple constituents of the air, so to speak, are about one-fifth oxygen and four-fifths nitrogen gases, with about two parts perhaps in a thousand of carbonic acid; and although, as we too well know, the air is occasionally polluted by many additions, yet, whether we take air from the top of mont blanc, or a cellar in london, the staple principles of oxygen and nitrogen have their proportions unchanged. the air breathed by animals who live in the water is somewhat differently constituted; the proportion of oxygen is considerably greater, probably about as much as one-third or thirty-two parts in one hundred; so that fish breathe a more highly oxygenated air than we do.

now it is found that, when we inhale the air of the atmosphere (that is to say, one-fifth oxygen and four-fifths nitrogen), we expire some oxygen, some carbonic acid, and some nitrogen also; and to ascertain the actual changes which took place, was the object of abernethy's inquiry.

the subject is one of great interest to the public; and, in justice to abernethy, we should remark (that which perhaps a few more years may render it more important to record), that this essay was written more than half a century ago—1793.

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thousands die every year of affections of the lungs; and many diseases of these organs, if not in their nature incurable, have too generally in practice proved to be so. there are not wanting, however, many persons who ascribe these mournful results, not so much to the abstract difficulty of the case, as to imperfect and erroneous views of the functions and relations of these important organs; and who entertain the opinion that the investigation of the subject has been, either from preconceived notions, from a too limited view of the phenomena, or from some other cause, so infelicitously conducted, that the conclusions arrived at have been either merely assumptions, extremely doubtful, or absolutely erroneous.

it is sufficiently obvious that if we are ignorant of the use of any part of a machine, it must be the most unlikely thing in the world that we should know how to set about repairing it when it is out of order; and the matter must be still worse, if we should happen to ascribe to certain parts of it purposes different or contrary to that which they as really fulfil. so, in an animal, if we are ignorant of the use and relations of any organ, it is very improbable that we can understand the nature of its disorders, or treat them in any case successfully, except by the merest accident, which, though it may waken us up to a sense of our ignorance, leaves us so blind to the causes of our success that we have no power of repeating it.

now this is pretty much the actual state of affairs in respect to diseases of the lungs. no investigation of any organ is worth anything, unless it include its relations with other organs in the same machine.

what should we ever learn by looking at the mainspring of a watch, apart from the general machinery to which it belongs? though we should look for ever, and employ a microscope to boot, it is clear we should never arrive at the perception of its true relations.

abernethy's inquiry derived great interest from the investigation of the skin by which it was preceded, and which seems to have formed his primary object. a few words on this wonderful organ may help the unprofessional reader to form some estimate66 of its relations and importance. as, in all animals, it is the surface in immediate contact with external influences—the first which attracts our notice—the first which we instinctively interrogate as to the state of the animal, so it is of all others the first which presents to us the evidence of design and adaptation. we tell the climate an animal inhabits, with moderate certainty, by looking at the skin; and if we occasionally meet with apparent exceptions, further examination usually shows that they exemplify the more strikingly the unity of plan. thus we may find animals who inhabit hot regions furnished with a somewhat warm covering of the skin; as the tiger, for example: but when we examine the eye, and inquire into the habits of the animal, we find that he preys or feeds at night, when the atmosphere is charged with damp and cold.

we know that the animals whence we obtain our furs inhabit cold regions. the changes in the same animal are not less instructive. animals placed in certain circumstances, in which they require greater warmth, have increase of covering, and vice versa. again, the tendency to become white, in those inhabiting cold regions, is a very interesting adaptation, although i am not aware that it has been satisfactorily explained. two things, however, are certain: that they are placed in different circumstances as regards the relation to heat, and would reflect a great quantity of light, which, in its intensity in snowy regions, might be prejudicial, as there is no doubt of the influence of this principle in animals. again, it is a very common arrangement that animals should take the colour of the ground they occupy; and this is sometimes very curiously exemplified. i have observed in the common hunting-spiders which inhabit some palings in a garden in the country, that they are of different shades, but they all more or less resemble that part of the old paling on which they are found. those which we see on the ground are generally of some dark colour. birds exemplify in a very remarkable manner the adaptation of their external coverings to the requisitions which their habits establish. all animals may be said to be surrounded by an atmosphere of their own, and they are not therefore, strictly speaking, in contact with the atmosphere; but67 when they are exposed to air in motion, this stratum is blown aside, and the atmosphere is brought in contact with the surface. its refrigerating influence is now felt; and, just as a boy cools his broth by blowing on it, a fresh stratum of cold air is constantly brought to the surface.

the power of resisting or limiting this refrigerating influence is somewhat differently conferred in different animals: in the healthy human subject, by increased activity of the vessels of the skin, which induces greater heat. birds, in their rapid flight, and especially in the more elevated regions of the atmosphere, are exposed to intensely refrigerating influences. these are met by the surface being clothed first by fine feathers, the worst of all conductors of heat, and these are overlapped, where they meet the atmosphere, in such a way that the bad-conducting property of the feathers is increased by the mechanical arrangement of them. again, the respiration of birds, which (as we contend) is a refrigerating process, is very restricted; although, for want of due consideration of all the circumstances, and especially of certain analogies afforded by insects, very opposite views have been entertained. domestic animals (birds inclusive) impressively suggest the refined adaptation of colour even, of the whole surface, to the altered position of the individual. nothing is more striking than the general uniformity of colour in wild animals—few things more familiar than their infinitely varied hues when domesticated. now it is certain that these differences have a meaning, and that their relations are important; but when we extend these thoughts from the coverings of animals to the consideration of surface, whether of animals or vegetables, what wonderful things occur to us. every variety of colouring which we observe in domestic animals, every spot on an insect's wing, every pencilling on a a flower, places the individual in a different relation, so far, to light, heat, and other powerful agents in nature.

or if we look from another point of view—we cannot walk by a hedge-row in summer without observing how very small the differences of light and aspect are, which seem on the same soil to confer on the same species of flowers such numerous varieties68 of colour. i have most frequently observed this in the common cranes-bill, or wild geranium.

in order to estimate correctly the value of these surfaces to the animal or vegetable, it is obviously of great importance to us to know what they do; and if they give off any thing, to ascertain its nature. that either animal or vegetable may be healthy, the processes of nature, whatever they are, must be carried on; and we may be assured, that the fragrance of the rose is just as necessary an exhalation from the plant, as it is an agreeable impression to us.

but all animals may be said to breathe quite as much by their skin as by their lungs. leaves, too, are the breathing surfaces of vegetables; and, therefore, to ascertain the facts in the one, without inquiring into those observable in the other, would be likely to fog our reasoning and falsify our conclusions. the first impression we obtain from all animals is from external form and appearance—from, in fact, its outward covering. it was the first organ to which abernethy devoted his most particular attention; and here again his investigations show how little those knew of his mind who imagined that his thoughts were restricted to any one set of organs.

in whatever light we view it, the skin is, in all animals, a most important organ; and so much so, as—drolly enough—with the exception of the human subject, to have been long popularly so considered. yet so imperfect have been the investigation of its functions, that we are at this moment chiefly indebted to the early experiments of abernethy for what we know that is positive on the subject. the original experiments of sanctorius were quantitative and, as general truths, of sufficient importance to have excited more attention. cruikshank's were highly acceptable; but they were less numerous and less varied than those of abernethy; whilst the labours of edwards, though exhibiting great industry and zeal, were by no means so conclusive as those of abernethy. edwards' experiments served to strengthen and confirm, by the analogy afforded by other animals, conclusions drawn by abernethy from the more secure premises furnished by the observation of corresponding functions in man.

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mr. abernethy's inquiry was first directed to ascertain what the skin actually gave off from the body; and secondly, what changes took place in the air which we draw into the lungs (inspiration). we will endeavour to give some idea of these experiments. they were very simple—they involved no cruelty, like those of edwards—and they were many of them such as the public might repeat without difficulty.

very useful would it be, if persons who have leisure would sometimes engage in physiological inquiries. they would find them to be extremely interesting; and a series of facts would be easily collected, from which the physiologist might obtain the most valuable information, but which, engaged as most of us are in applying physiology to the correction of disordered functions, we can seldom collect for ourselves, except in a few hours stolen from those occupied in an arduous profession, and perhaps by the sacrifice of paramount duties.

mr. abernethy's experiments were very numerous, and commenced in the summer of 1791; but the winter's cold obliging him to desist, they were renewed in the spring of 1792. having referred to the experiments of ingenhous and cruikshank, together with an allusion to a paper (not then made public) by lavoisier, he proceeds to describe his own.

having a trough containing a large quantity of quicksilver, he filled a glass jar (sufficiently capacious to contain his hand and wrist) with that metal. he inverted it into the trough in the usual way of proceeding in collecting gases. he fixed the glass jar in a sloping position, that he might introduce his hand the more readily beneath the quicksilver. in this way, whatever was given off from the skin of the hand, rising through the quicksilver to the top of the glass, and of course displacing a proportionate quantity of quicksilver, could be made the subject of analysis.

he describes his first experiment as follows: "i held my hand ten minutes in the jar beneath the surface of the quicksilver, and frequently moved it in that situation, in order to detach any atmospheric air that might accidentally adhere to it, and afterwards introduced it into the inverted jar. the quicksilver70 soon acquired a degree of warmth which rendered it not unpleasant. minute air-bubbles ascended to the top of the quicksilver, more speedily in the beginning of the experiment, more tardily towards the conclusion. after an hour had elapsed, i withdrew my hand; the bubbles of air, which now appeared on the top of the quicksilver, were, i suppose, in bulk equal to one scruple of water.

"in sixteen hours, i collected a half-once measure of air, which makes fifteen grains the average product of an hour. no kind of moisture appeared on the surface of the quicksilver. some sucking-paper was put up, which was withdrawn unmoistened. my hand was always damp when taken out of the quicksilver. whatever aqueous perspiration was produced, adhered to its surface, whilst the aeriform ascended to the top of the jar. to the air i had thus collected, i threw up some lime-water20, when about two thirds of it were rapidly absorbed; to the remainder, i added a bubble of nitrous gas21; but could not discover any red fumes, nor any diminution of the quantity. i repeated this experiment six times, with similar though not uniform results. i believe it will be found that the air perspired consists of carbonic acid gas, or fixed air, a little more than two thirds; of nitrogenous gas, a little less than one-third. in one experiment, the nitrogen made only one-fourth part of the air collected; in another, i thought it exceeded one-third."

he then made a series of experiments of the same kind, but substituting water for the quicksilver, sometimes heating himself previously by exercise. the results of these were not materially different from those in which he held his hand in quicksilver; but they are less clear, because the carbonic acid gas given off seemed absorbed by the water. in the next series of experiments, he held his hand and arm in atmospheric air. in this case, he found that, in addition to the giving off of carbonic acid, a portion of the oxygen of the air became absorbed. this is71 exactly what happens in the lungs. now, as the carbonic acid, when given off, is in both cases coincident with the disappearance of oxygen, and as carbonic acid is composed of oxygen and carbon, it had been usually conceived that the oxygen taken in, contributed to form the carbonic acid given off; and the idea is still entertained very generally.

the experiments of abernethy, however, presently to be adverted to, in regard to the skin; and those of edwards, long after, in regard to the lungs; satisfactorily prove, we think, that the carbonic acid is not at all derived in the manner supposed22.

to test this matter, mr. abernethy confined his hand and arm in various gases containing no oxygen—as hydrogen, and then in nitrogen; but he found the carbonic acid gas still given off as before. he then placed his hand in a gas (nitrous oxide) containing oxygen; and lastly, in oxygen itself, to see if it increased, or otherwise affected the elimination of carbonic acid; but in neither of those experiments was the carbonic acid thrown off, increased, or in any way affected by it.

in a subsequent part of the paper, he remarks on the idea that physiologists entertained of the carbonic acid given off by the lungs being made by the oxygen inspired; but he says, very justly, that the quantity of oxygen is too small for the formation of so much carbonic acid gas as we find given out by those bodies; and that his experiments on the skin clearly prove that the exhaling vessels of the skin emit carbonic acid in a state of complete formation; and then adds, what it is difficult to estimate the merits of, without recollecting that it was said half a century ago (and before the experiments of edwards), "and, doubtless, those of the lungs perform a similar office."

this is one of those bold, and, we believe, successful reasonings from analogy which were very characteristic of abernethy.72 the truth is, that even the experiments of edwards, some of which were, a long time since, repeated by ourselves, with the same results, are not, i conceive, so conclusive as the analogy of abernethy. it is true, they consisted of placing frogs and other animals in gases not containing oxygen, when it was found, notwithstanding, that there was no diminution in the quantity of the carbonic acid produced, and which therefore could not have been compounded of any oxygen in the gas. but even here many possible sources of fallacy suggest themselves. the previous expulsion of all the oxygen from the animal is obviously a matter of uncertainty. there are, besides, those sources of fallacy which are inseparable in some form or other from all experiments on animals which disturb their natural habits, especially when these disturbances are so great as to amount to suffering. from all such experiments abernethy instinctively shrunk. his repulsion to them seems not to have rendered it necessary to him to have shown that they were as physiologically inconclusive as they were morally questionable. at all events, his present experiments were not obscured by any such sources of fallacy.

still the idea of the carbonic acid exhaled by the lungs, being made up of the union of the carbon exhaled with the oxygen taken in, continued to be very extensively entertained. we can only say that to us it seems entirely a child of the imagination; what horace calls

"mentis gratissimus error;"

and shows not only how few people can find leisure to investigate, but how few venture to observe or think for themselves. abernethy also experimented by holding his hand in carbonic acid, when he found that in about nine hours, three ounces, by measure, of carbonic acid were absorbed by the skin; and in the remaining gas, a considerable quantity of other gas which had been given off, which appeared to be nitrogen.

desirous of ascertaining the quantity of carbonic acid gas given off by his hand, in different gases in a single hour, he introduced his hand into various gases. in the experiment with

73

? drs.

nitrous oxide, there came off 6

hydrogen 4

atmospheric air 3

the test for the carbonic acid was, as before, in all cases, lime-water. he also found that the skin absorbed oxygen much more readily than most other gases. one remarkable experiment we will notice, to show how laborious all these investigations were, and for the interesting nature of the result. he placed his hand alternately in vessels containing each twenty-four ounces, by measure, of nitrogen and oxygen gases. after eight hours' exposure in each, two-thirds of the oxygen had disappeared, whereas only one twentieth of the nitrogen was absorbed. indeed, there is no one feature of these experiments perhaps more interesting than those which suggest the stronger aptitude of the skin to absorb oxygen in comparison with other gases. for example, abernethy found that the skin absorbed, by measure,

? ozs.

of oxygen gas, in eight hours 8

of nitrous gas, in five hours 3

of hydrogen, in five hours 1?

of nitrogen, in eight hours 1

mr. abernethy then made some experiments on his own lungs, after the manner that mr. cruikshank had done, to find the quantity of water exhaled, by breathing into glass jars filled with and inverted in quicksilver, and by other methods, and also to ascertain the change produced in the air by respiration. these are all interesting; but we can only give general results, referring to the work itself, as full of material for thought and future observation. he considered that, on the whole, the change in the air was, that in one hundred parts, consisting of

? parts.

nitrogen 80

oxygen 18

carbonic acid 2

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about three parts of the oxygen were absorbed, whilst about twelve parts of carbonic acid were exhaled, the nitrogen being little altered, or even receiving some small addition. the quantity of inspired oxygen which disappeared varied in different experiments, probably depending on the depths of the inspiration, and the duration between it and the following expiration—the time, in fact, during which it was retained in the lungs. the smallest quantity which disappeared was one-twelfth; the largest, one-sixth. the moisture (water) exhaled, he found to be about three drachms in an hour.

these experiments, for the particulars of which we must refer to the book itself, contain a calculation of the extent of surface of the body, which he estimates at about two thousand seven hundred square inches—that is, about thirty-eight times that of the hand and wrist, on which he experimented. thus, if we multiply any of the results he obtained by thirty-eight, we shall obtain some idea of the prodigious power of this wonderful organ, and of the vast influence which its various conditions must exert on the whole animal economy. the whole of the experiments in the paper are just as interesting as ever, and would, we are well persuaded, be found amply to repay further investigation.

they exemplify in every line his clearness of thought, and his care in deducing no other conclusion from the premises than that which they logically justify. the observations which he has annexed to his paper also are just, and of great practical value; they discuss the bearing that the whole has to the relation which exists between the skin and lungs, and the influence of this on the causes of that fell destroyer, popularly known under the title of consumption.

they are a portion of that investigation of relation between various organs, on which anything like the formation of a definite and practical science must ultimately depend. we shall endeavour, in the sequel, to explain the ulterior consequences which necessarily arise out of such considerations, when they are duly followed out. we shall endeavour to point out the share they had, in conjunction with other considerations, in leading to those75 beautiful and simple principles which mr. abernethy was led more especially to advocate; and show how far he went, as describing the starting point of those who have endeavoured at a fuller development of the consequences of his views.

he remarks, justly enough, on the determination to the lungs consequent on the repression of the surface, and the necessary additional duty thrown on those important organs engaged in a common function with the skin, where the duty of the latter is not performed; and on the elements thus supplied for disease, especially in persons of restricted chest; relations, be it remembered, which exist between the various other organs of the economy, and which exemplify in a single case truly, what has been, we trust, since shown in regard to organs generally; how the organ, which may be the seat of the disease, may not be the seat of the original cause, but really a secondarily affected organ—a hint which, when followed out, is of immense practical importance.

the skin is by no means the only organ which has a community of function with the lungs, or through which these important parts become affected; but if this be so, and diseases of the lungs be treated as an integral thing, it requires no great penetration to see how diseases so handled must be incurable; since the real cause may never be ministered to.

again, if a case should be successfully treated, by means which afford all possible relief to the lungs, whilst the primarily affected organ is also properly treated, it by no means follows that the treatment should be the same in every case; for the primarily affected organ may be different in different cases. there is, in fact, no organ of the body which, when subjected to disordering influences, may not secondarily affect the lungs.

the liver is especially apt to affect them. it is engaged, like the lungs, in throwing off large quantities of carbon or charcoal from the system, and has been not very improperly termed the "abdominal lung." it is constantly also sending through the medium of the heart a large quantity of blood to the lungs. now, if this blood have not the proper quantity of carbon extracted from it by the liver, or if even the blood be excessive in76 quantity, why the lungs must have more to do; and many diseased lungs have been produced in this manner in cases where the chest has been well formed.

there are, however, many intimate relations between organs which do not depend on mere community of function. it is very important that the public should have clear views on this subject; and if they would only give a little of that attention which they so often bestow on things infinitely more difficult, there is no doubt many lives would be saved that are irremediably damaged, as abernethy says, sometimes even before any symptoms have suggested that there is anything the matter.

but if there be a shadow of truth in mr. abernethy's views, and still more in those extensions of them to which they have naturally led, we may learn how necessary is that discrimination which traces disease to primarily affected organs; and how little success we may expect by treating the lungs, as the integral seat of disease, by specifics, or such remedies as tar, naphtha, cod-liver oil, various gases, &c. which come in and go out of fashion in a manner sufficiently significant of the claims they can have in a scientific point of view.

mr. abernethy also remarks on the comparatively restricted influence of scrofula in constituting consumption. "at one time," he observes, "i examined the bodies of many people who died of consumption." after describing other appearances which he found, he says, "the greater number were bestudded with larger or smaller tubercles, or made uniformly dense (consolidated)." he says, this disease (consolidation) is very insidious, that it is often established beyond the possibility of removal before it is suspected; but, he says, he thinks it might be known, for the capacity of the lungs is diminished; and suggests that this should be tested, by allowing a suspected case to breathe into a glass vessel over water, by which the quantity of air they can receive is rendered perceptible.

his remarks, too, on the treatment are highly interesting and discriminative, and will not only well repay attentive perusal, but that study which is necessary to the perception of their full force and beauty. when we have to sum up the various influences77 of the views of abernethy, we may probably find space for a few facts on that which they exert on the treatment of the lungs and skin; and this not merely as affecting the health in general, but also complexion, and other conditions of these curious and important organs.

we are unwilling to dismiss this paper without directing attention to the illustration it affords of the erroneous views of those who imagine that abernethy's investigations were confined to the digestive organs, and still less, of course, to one of them (the stomach). it would, on the contrary, be difficult to find any paper on physiology so comprehensive in its views, so simple and clear as to its object, so cautious and logical in its reasonings, so free from any bias, or with so little reference, either directly or indirectly, to what are usually understood by the digestive organs. on the other hand, it is an investigation which (as regards the relation which exists between two organs having a common function) is an exact type of what physiological investigation should be. for we have only to extend the idea of a relation which exists between two organs, to those which exist between all organs; to regard as their combined functions, the sustentation of the life and health of the individual, just as we have been regarding respiration, the common function of the skin and lungs; and we thus arrive at what must be the basis of any sound or comprehensive inquiry into the true relations of the various parts of the economy; by which alone we can interpret the phenomena of health and disease.

moreover—however presumptuous the assertion may appear on the one hand, or however humiliating the view it implies of the present state of medicine as a science on the other—we must regard this investigation, in every philosophical sense of the term, as still among the "means untried" of the illustrious author whose words we have ventured to place at the head of this chapter.