"all things are but altered, nothing dies,
and here or there the unbodied spirit flies."
dryden.
the most universal character impressed on all created things that sense allows us to recognize, or philosophical inquiry to demonstrate, is "change."
while nothing is more certain, few things pass less observed; or, when first announced, more stagger conviction.
an old man sees the yew-tree of his boyish days apparently the same. gilpin tells us "eight hundred years is no great age for an oak17!"
the cliff which we left "beetling" seems to beetle still; mountains appear to be everlasting; yet, were seas and rivers to disclose even a small part of their mission, the danube or the volga might tell of millions of tons of soil carried from higher levels to the black sea and the caspian. animals, too, are mighty agents in recording the mutability of the matter of the universe. coral reefs, never spoken of in smaller terms than miles and fathoms, are the vast ocean structures of countless millions of animalcules, which serve, as it were, to link together the two great kingdoms of organic nature—the animal and vegetable creation. the microscopic geologist informs us of whole strata, well-nigh entirely composed of the silicified skeletons of insects. sir charles lyell further impresses on us the reality of continual change, by referring (and, as it would appear, with increasing probability) even42 the stupendous changes demonstrated by geology to the agency of causes still in operation.
animals, however, besides the curious structures which they combine to contribute, are individually undergoing constant change. man is not only no exception, but he is a "glaring" example.
the whole human race are in hourly progress of mutation. "in the midst of life we are in death," is a truth to which physiology yields its tribute of illustration. every moment we are having the old particles of our bodies silently taken away, and new materials as silently laid down. surrounding influences, as air, moisture, temperature, &c. which, during life, are necessary to existence—the moment the breath leaves us, proceed to resolve the body into the elements of which it was composed. in all cases, change may be regarded as the combined result of two forces: the force acting, and the body acted on—that is to say, of certain external agents and certain forces inherent in the thing changed.
animals are no exceptions to this view, and diseases are amongst a multitude of other exemplifications of it; but, in order to distinguish these more clearly, it is desirable that we should be familiar with those more ordinary changes in the body which are constantly going on; and to some of these were abernethy's early investigations directed.
in proceeding to give some account of his works, we must be necessarily more brief than a scientific analysis would require.
to do him full justice, it would be necessary to republish his writings, with appropriate commentaries. we shall hope, however, to do enough to relieve his memory from some of the numerous misconceptions of his principles and opinions; and to endeavour to show his claims to the respect and gratitude of posterity.
in everything abernethy did, we find evidence of the acuteness of his mind, and his general qualifications for philosophical research.
his lectures had gradually attracted an increasing number of students; and he seems, about 1791, to have been desirous of43 prefacing his lectures on anatomy by discussing the general composition of animal matter.
the rapid advance of chemistry had given a great impetus to this kind of investigation. abernethy was not only well up in the chemistry of the day, but also not unskilled in the manipulatory application of it; and he felt interested in observing the great diversity of substances which appeared to be made up of similar elements. boyle has recorded a vast number of facts, many of which would even now well repay a thoughtful revision; and fordyce was certainly one of our most philosophical physicians.
boyle had grown vegetables in water and air only, and found they produced woody fibre. fordyce found that gold fish, placed under similar conditions, not only lived, but grew. abernethy's experiments had for their object to inquire how far organized bodies (animals and vegetables) were capable of deriving their various structures from similar simple elements.
he grew vegetables on flannel, wetted from time to time with distilled water; and then, analyzing them, compared the results with those of the analysis of vegetables grown in the ordinary manner.
other curious experiments consisted in pouring concentrated acids on vegetable structures, with a view to dissolve any alkali or iron which they might contain, and then analyzing the vegetables so treated.
he now found, in the burnt vegetable, lime, iron, &c. which, had they been free to combine, should have been taken up by the acid to which he had subjected the vegetable before he analyzed it; but he found neither in the acid, whilst both were discovered in the vegetables.
he also inquired whether tadpoles and leeches would live when kept only in distilled water, with the admission of air. for example, he placed twelve leeches in two gallons of distilled water, they weighed, in all, twelve scruples. in three months, two had died, but the remaining ten weighed twelve scruples, showing that they had grown. he next inquired whether vegetables, grown in air and distilled water, would admit of further conversion into the structure of animals; and, for this purpose,44 he fed rabbits on vegetables so reared. his rabbits appear to have eaten about six plates at a meal of young cabbages thus reared on flannel wetted with distilled water.
he also experimented on eggs, both before and at the time of incubation.
he wished to ascertain the quantity of lime in the chicken and the egg, respectively; and whether any of the lime was absorbed from the shell, which it appeared not to be.
it is curious to observe the time and labour he gave to these experiments; they evince a very perfect knowledge of the chemistry necessary; whilst the circumstances calculated to interfere with or obscure the conclusions from them are judiciously and clearly stated.
many of his remarks, as well as the ingenious suggestions with which they are interspersed, exemplify the caution with which he reasoned. in speaking of his experiments on leeches and tadpoles, many of which latter had become perfectly developed frogs, he says: "the experiments which i made on this plan (in vessels of distilled water, covered with linen) were made in the summer, when to prevent vegetation was impossible; and, on the other hand, when the vessels were covered over, even leeches died. in the winter, vegetation might cease; but then the torpid state of the animals would render the experiments inconclusive."
he reduced an equal number of eggs and chickens (at the time of incubation) to ashes; sometimes in crucibles, sometimes in retorts. on the ashes he poured some distilled water, and ascertained the salts (as lime, &c.) contained in them. in some experiments, the quantity of these found in the ashes of the chickens greatly exceeded that found in the ashes of the eggs. in other experiments, the quantities were equal.
in some of his experiments, after using the best chemical tests for detecting iron, lime, and the salts, and then washing the residue with distilled water, he burnt it in a crucible, and found more lime and iron; on which he makes the following remarks, which suggest what we apprehend, even at this time, is a very necessary caution:
45
"this circumstance proves to me that the substances found in the ashes of burnt animal matter do not formally exist in the mass before its destruction, but are only new distributions of the same ultimate particles which, under their former mode of arrangement, made the animal substance; but which, being driven asunder by the repulsive power of fire, are left at liberty to form other modifications of matter." page 97. just what happens when animal matter is burned, in the formation of ammonia, by the union of the nitrogen and hydrogen then set free.
he investigated, also, the question of how far the results of the decomposition of animal matter would be identical, if the analyses were conducted by heat, or by putrefactive decomposition. in this experiment, he selected blood; and he found that blood which had been allowed to putrify yielded a much larger quantity of iron and lime.
the whole of the experiments are very suggestive, and full of thought; and not only indicate very forward views of the elementary constitution of organic and inorganic matter, but also moot questions which have not lost any of their interest by the most recent investigations. he concludes by observing that he had undertaken these experiments for the reasons already assigned, and because he had imbibed the idea that the ultimate particles of matter were the same.
he remarks that the progress of chemistry had not been applied, in every respect, to the best purpose; that men's views were becoming contracted by being directed to individual objects; and that they had ceased to contemplate the beautiful and extensive subject of matter and its combinations; and he complains that even fourcroi, lavoisier, and chaptal, either avoid the subject, or do not sufficiently consider it. we must recollect this was said before sir h. davy had made his splendid discoveries. abernethy, after observing that he hopes his experiments will induce others to investigate the subject, concludes thus:
"i know not any thought that, on contemplation, can so delight the mind with admiration of the simplicity and power46 evident in the operations of the creator, as the consideration that, by different arrangement and motion of singular atoms, he has produced that variety of substances found in the world, and which are so conducive to the wants and gratification of the creatures who inhabit it."
dissection of a whale.
section i.
"mors sola fatetur
quantula sint hominum corpuscula."
?
juv.
amongst a multitude of examples, which teach us how little we can infer the importance of anything in nature from its size, or other impressions which it may convey to mere sense, we might adduce the wonderful little tubes, certain relations of which were the objects of this paper. those constant mutations in animal bodies which are every moment in progress, are, in great part, due to a very curious order of vessels, of such extreme minuteness and tenuity, that, being in the dead animal usually empty and transparent, they are very commonly invisible, and thus long eluded discovery. there is one situation, however, in which circumstances combine to expose them to observation. transparent though they be, they are here usually rendered visible; first, by being loaded with a milk-like fluid; and secondly, by being placed between the folds of a membrane, itself beautifully transparent (the mesentery). this fluid they have just taken up from the digestive surfaces on which their mouths open, and they are now carrying it off to pour it into the blood-vessels, that it may be added to the general stock of the circulation.
in the situation above mentioned they were at length discovered, about the commencement of the 17th century. every thing destined to support the body with new material, as well as the old, which is to be taken away, must first be sucked up by the myriads of47 inconceivably minute mouths of these vessels, which, from their office, are called the absorbents. these absorbents may therefore be regarded as the sentinels of the body. they are very sensitive and excitable; but, besides this, there are placed in the course of their journey, from the surfaces whence they bring their contents, and the blood-vessels to which they are carrying them, a number of douaniers, or custom-house officers (the glands, or kernels, as they are popularly called), whereby, as we have every reason to believe, the fluids they are importing are subjected to rigid examination; and, if found to be injurious, to some modification, tending to render them more fit for admission into the system.
if the contents are very irritating, these vigilant guards—these kernels—become very painfully affected, and sometimes inflammation is set up, sufficient even to destroy the part; as if, faithful to their trust, they perished themselves, rather than give entrance to anything injurious to the body.
we should never advance, however, in our story, if we were to tell all the interesting peculiarities of these curious vessels.
when first discovered, and the office assigned to them could no longer be disputed, the general distribution of them was still doubted. as it was usual to render them visible by filling them with quicksilver, so, with a kind of reasoning which has too often characterized mere anatomical research, when they could not be made visible, it became the fashion to doubt their existence. amongst other structures, bone was formerly one in regard to which people found a difficulty. how could such delicate vessels exist in such an apparently dense structure? but mr. abernethy, who, like bacon, had always opposed mere eye-reasoning, used to observe, with equal simplicity and good sense, that, for his part, he could see no more difficulty in an absorbent taking up a particle of bone, than he could in comprehending how a vessel could lay it down, which nobody doubted. we now know that bone is not only supplied with all the vessels which characterize a living structure, but so liberally, that, in comparison with some other structures of the body, we regard it as a part of high organization.
nevertheless, the extreme minuteness and transparency of48 these absorbent vessels naturally led persons to regard with considerable interest any magnified view of them, such as that afforded by larger animals. in the paper before us, which was published in the "philosophical transactions" for 1793, mr. abernethy gives the account of his examination of the absorbents in a whale; and his object was to help to determine a question long agitated, whether the glands or kernels were composed of cells, or whether they were merely multiplied convolutions of vessels. he selected the absorbents from the situation to which i have already referred. he threw into the arteries which carry blood to nourish the gland, a red solution containing wax, which of course became solid on cooling; and into the veins which return the blood from all parts, a similar solution, only coloured yellow. he filled the absorbents with quicksilver.
he found, in filling the absorbents, that wherever the quicksilver arrived at a gland, there was a hesitation—its course became retarded, and that this retardation was longest at those glands which were nearest the source whence the vessels had drawn their contents, viz. the alimentary canal: as if the surfaces over which the fluid had to pass were more multiplied where most necessary, or, recurring to our metaphor, as if the more strict douanier had been placed on the frontier. he says that he found that some of the absorbents went over the glands, whilst others penetrated these bodies. that he found that the melted wax which he had thrown into the vessels had formed round nodules of various sizes. he then extended his examination of these vessels to those of horses and other large animals; and the result of his investigation was, that it inclined him to the conclusion that the glands were not merely made up of convolutions of vessels, but were of a really cellular structure.
the paper is very modestly put forth, and he concludes it by observing that he offers it merely for the facts which it contains, and not as justifying any final conclusion; but "as all our knowledge of the absorbents," he continues, "seems to have been acquired by fragments, i am anxious to add my mite to our general stock of information on the subject."
it may not be uninteresting to some unprofessional readers49 to know that the glands here alluded to are the organs which are so seriously diseased in those lamentable conditions popularly expressed, i believe, by the term mesenteric disease, or disease of the mesentery.
section ii.
curious cases published in the "philosophical
transactions," 1793.
"the universal cause
acts to one end, but acts by various laws."
pope.
however paradoxical it may appear, it is not the less true, that nothing more teachingly impresses the inquirer into nature with the actual presence of general laws than the apparent exceptions to them. finite capacities in dealing with the infinite must of course encounter multitudes of facts, the meaning of which they cannot interpret—portions of the divine government, as butler has said, which they do not as yet understand.
in philosophical investigations, these are properly regarded as facts which, in the present state of knowledge, cannot be made to fall under any of our very limited generalizations.
at one period, departures from the ordinary structure or form in animals were simply regarded as unintelligible abstractions, and no more philosophical expression was given to them than "lusus natur?"—sports of nature. progressive science, however, has thrown considerable light on such phenomena, and invested many of them with a new interest.
physiologists have not arrived at the explanation of all such facts; but much has been done by comparative anatomy to show that many of them are merely arrests of development, and cases of interference with the ordinary law.
that, in fact, they show the mutual harmony and connection50 of the laws of nature to be such, that the development of any one law implies the concurrence, so to speak, of some other, just as the successful incubation of an egg, or any other familiar fact, implies the presence of certain conditions. we cannot boil a drop of water without the concurrence of various laws: we say it boils ordinarily at 212° of fahrenheit; but how many conditions this involves!
until understood, how few could have guessed that mechanical pressure could have so modified the degree of heat necessary, as to exalt it to more than double, or reduce it to less than half; and again, how few would have looked for the force which, under common circumstances, governed the point at which water was thus converted into steam, in the pressure of the atmosphere; yet so mutually influential are these conditions—namely, heat and a certain pressure in modifying this change of form or matter—that some of faraday's most interesting results in experimental chemistry (we allude to his reducing several gaseous bodies to the liquid form) were obtained by abstracting heat and increasing pressure.
it is of very great consequence to remember these interferences in relation to disease, because most diseases may be regarded as examples of them. considered as "abstract wholes," as entities—diseases are necessarily unintelligible: but when looked at as natural processes obscured by interferences (if the inquiry be conducted with strict observance of those principles which are essential in all philosophical researches), they either at once become intelligible, or, at least, as open to investigation as any other facts in natural philosophy.
when we investigate the laws of nature with a view to the development of the sublime objects of natural theology, the concurrence of the various conditions, necessary to the most ordinary phenomenon, inclose the most irresistible proofs, from natural evidence, of the unity of the creator.
regarded in the light of facts which we as yet may not be able to generalise, the cases here recorded by abernethy are very interesting; although it is to be regretted that both cases were bodies brought in for dissection, in times when the circumstances51 baffled, if they did not forbid, any inquiry into the histories of them. it is lamentable to think of the state of the law with respect to anatomy at that time.
any surgeon who was convicted of mala praxis, resulting from ignorance of anatomy, was severely fined, perhaps ruined; and yet so entirely unprovided were the profession with any legitimate means of studying anatomy, that they could only be obtained by a connivance at practices the most demoralizing and revolting.
bodies were, in fact, chiefly obtained by the nightly maraudings of a set of men, who, uninfluenced alike by the repulsions of instinct or the terrors of law, made their living by the plunder of grave-yards.
many a tale of horror, no doubt, might be told on this subject.
graves were very commonly watched; and severe nocturnal conflicts occurred, which were conducted in a deadly spirit, not difficult to imagine. we believe all this has passed away; there is no necessity now for such revolting horrors. the public began to think for themselves, the real remedy for abuses. but to our cases. both were curious; the one was the body of a boy, who did not appear to have been imperfectly nourished, but in whom the alimentary canal was found to be less than one-fourth of its natural length, and in which also the relative length of its two grand divisions was reversed. the smaller in diameter, usually very much the longer, was so unnaturally short, as not to exceed in length more than one half of the more capacious but normally shorter division of the canal.
the other case presented a no less curious departure from the ordinary arrangement of parts than a reversed position of the heart; which, instead of being placed with its point as usual on the left side, was found to have that part situated on the right. in the natural condition of things, there is a difference on the two sides of the body, in the manner in which the large vessels are given off to supply the head and upper extremities. these differences existed, but were reversed; the arrangement of vessels52 ordinarily found on the right, being here on the left side, and vice versa.
in all this, there would be nothing to prevent the heart from pumping the blood to all parts in the natural way. but another very singular arrangement was found in relation to the liver. to the unprofessional reader we should observe, that usually, whilst all other things are made, or secreted as we term it, from the purer or arterial blood; in the human body, the bile is secreted from a vein which enters the liver for that purpose.
now, in the case before us, this great vein never entered the liver at all; so that here the bile was separated, like other animal fluids, by the arteries. the arteries going to the liver were found much larger than usual.
mr. abernethy examined the bile by submitting it to various tests; and comparing the results with those obtained from ordinary bile, he found them to be the same. his remarks are, as usual, ingenious and to the point, and very characteristic of the penetrative perception with which he seized on the proximate and practical relations of facts. "when we see the unusual circumstance," says he, "of secretion taking place from a vein18, we are apt to conclude that the properties of such a secretion require that it should be made from venous blood. but, in this case, we see that bile could be prepared from arterial blood; and we are led, therefore, so far to modify our conclusion as to infer, not that venous blood is necessary, but that it can be made to answer the purpose."
we must not omit that these remarks are supported by comparative anatomy. as we descend in the scale of creation from the more complicated organizations to those which are more simple in their structure or their relations, the arrangement which i have stated as usual in man no longer obtains, but the bile is secreted from the arteries as the other fluids of the animal—showing, in fact, that the inference drawn by abernethy was the legitimate conclusion.
53
since the discovery of this case, one or two others have been observed; and the opinions of several eminent men, in relation to the bearing such cases have on the ordinary sources of bile, are described in mr. kiernan's interesting paper on the anatomy and physiology of the liver, in the "philosophical transactions." it is very interesting, particularly to a professional reader, to peruse that discussion, in order to estimate mr. abernethy's comparatively simple, ready, and, as it would seem, correct view of the subject.
one other thing we learn from these cases—the extreme importance of examining bodies whilst their histories and symptoms can be recorded. it might have been highly useful to science, had the histories of these cases been known; and the circumstance should be mentioned, as, in some measure, tending to counterbalance in the public that not unnatural but (as regards their real interest) not less to be lamented aversion to the inspection of the dead—a branch only, it is true, but a very important one of physiological inquiry. it is the only means of which we can have the comfort of knowing that, however unable we may have been to arrest disease, we were at least right in the seat we had assigned to it; but it is infinitely more valuable in disclosing to us affections of organs which had given no sign, and in thus impressing on us the necessity of taking a wider range in our investigations, and comprehending in them all those injurious influences which have, at various periods, acted on the body; for we thus obtain an insight into the nature of disease which no mere present symptoms can ever afford us.
the repulsions which the public have to overcome are admitted; but let us not, in common justice, forget those sacrifices of time, labour, and too often of health also, which are made by the profession. nor is it immaterial to mention that it is a service for which they seldom receive any remuneration, the only incentive being one which, if it excite no sympathy, is at least entitled to respect—namely, the desire to improve their knowledge of their profession. there is no doubt of the deep and common interest which the public and the profession have in this question; and it is from that conviction that i have ventured on these few54 remarks. abernethy, when he introduced any subject in his lectures, was accustomed to say at once all that he intended to remark on it. i beg, in the foregoing observations, to follow his example, which i trust the reader will accept as an apology for the digression.
