Part 2

Blumenbach, Chausier, Dumas and Bichat, treat of circulation before absorption, on which it depends, and even before mastication, deglutition and digestion, on which, in general, even absorption itself chiefly depends.

If the arrangement of Chausier in particular, who, in this respect, is as accurate as any of them, were to be considered as indicating the relation and dependence of the functions, so absurd is it, that absorption instead of the cause, would be the result of nutrition, generation the result of absorption, and digestion the result of generation. Thus, by arranging effects in the place of causes, they confound the relations of the functions, and reverse the very order of their dependence.

The division of the functions into external and internal, as anciently proposed by Aristotle, and afterwards successively adopted and improved by Buffon, Grimaud and Bichat (the last of whom substituted for them the terms organic and animal) is still more faulty.

Anatomy, I divide into three parts, namely that which considers the mechanical or loco-motive organs, that which considers the vital organs, and that which considers the intellectual organs.

Under the mechanical or loco-motive organs, I class, first, the bones which support the rest of the animal structure; second, the ligaments which unite them; and third, the muscles which move them.

Under the vital organs, I class, first, the organs of digestion, the absorbent surfaces, and the vessels which absorb from these surfaces; second, the heart, lungs and blood-vessels, which derive their contents (the blood) from the absorbed lymph; and third, the organs of secretion, which separate various matters from the blood. Then follow the generative organs, which, though generally formed into a distinct class from the vital, ought not by any means to be so reckoned. For it is evident, that they form, as it were, the sequel of the vital organs, being dependent on secretion—the last of the vital functions, and destined merely to propagate vitality, and to communicate it to a new series of beings.

Under the intellectual organs, I class, first, the organs of sense, where impressions take place; second, the brain or organ of judgment, where these excite ideas; and third, the nerves, where volition results from the last.

This is a natural arrangement of the anatomy of animals, and its peculiar simplicity is illustrated by its involving, in application, that of minerals and vegetables, and by its being capable of instant adaption to physiological science.

In order to arrange Animal Physiology, it is only necessary to substitute the term “functions” for “organs;” and that science will likewise involve, in application, the physiology of mineral and vegetable bodies, and be, in its turn, capable of instant adaption to medical science.

Thus, the functions also are divided into Mechanical, Vital and Intellectual.

The mechanical functions are subdivided into that of support, that of connection, and that of loco-motion.

The vital functions are divided into that of absorption, that of circulation, and that of secretion.

The intellectual functions are divided into that of sensation, that of mental operation, and that of volition.

A circle of functions, I may observe, thus exists in animals, which exists not in minerals or vegetables, because volition, the last of the intellectual functions, connects itself to the mechanical ones, by rendering them subservient to it in loco-motion. Thus the first and the last of these functions are as intimately connected as any of the intermediate ones, and a beautiful circle of organic function and organic influence is formed.

The plan of the course will, therefore, be precisely the same with that which I have proposed for Anatomy and Physiology in general.

I. In that part of the course which relates to the mechanical organs and functions, will be explained the structure and uses, 1st, of the bones which support the rest of the animal machine; 2dly, of the ligaments which unite it; and 3dly, of the muscles which move it.

II. In the first part of the course which relates to the vital organs and functions, will be explained the structure and uses, 1st, of the organs of mastication, deglutition and digestion, of the absorbent surfaces, and of the vessels which absorb from these surfaces; 2dly, of the heart, lungs and blood-vessels, which derive their contents, (the blood), from the absorbed lymph; and, 3dly, of the organs of secretion, which separate various matters from the blood. Throughout this division in particular, the analogies from vegetables will be explained.

III. In that part of the course which relates to the intellectual organs and functions, will be explained the structure and uses, 1st, of the organs of sense which receive impressions from external objects; 2dly, of the brain, where these impressions excite ideas; and, 3dly, of the spinal marrow and nerves, where volition results from the last. In this division, will be also explained, as founded upon original observations, certain criteria of the various degrees of the sensitive, perceptive and voluntary powers possessed by different animals, as well as the nature of sensation, perception and volition themselves.

As in physiological enquiries, comparative anatomy and comparative views alone can destroy an hypothesis or transmute it into a theory, I shall throughout the course introduce all its principal facts.

The machines, says Cuvier, which are the object of our researches, cannot be demonstrated without being destroyed. We have no means of discovering what would result from the absence of one or several of their parts, and consequently we remain ignorant of the operation of each of these parts in producing the total effect.

Fortunately, nature herself seems to have prepared for us the means of supplying that want which arises from the impossibility of making certain experiments on living bodies. The different classes of animals exhibit almost all the possible combinations of organs. We find them united, two and two, three and three, and in all proportions; while at the same time it may be said that there is no organ of which some class or some genus is not deprived. A careful examination of the effects which result from these unions and privations is therefore sufficient to enable us to form probable conclusions respecting the nature and the use of each organ, or form of organ.

In the same manner, we may proceed to ascertain the use of the different parts of the same organ, and to discover those which are essential, and separate them from those which are only accessary. It is sufficient to trace the organ through all the classes which possess it, and to examine what parts constantly exist, and what change is produced in the respective functions of that organ, by the absence of those parts which are wanting in certain classes.

Thus, says Richerand, the cellular structure of the lungs which cannot be clearly demonstrated in man, on account of the excessive tenuity of their smallest lobuli, evidently displays itself in the vesicular lungs of salamanders and frogs; in the same manner, the scales covering the bodies of fish and reptiles, or the claws of birds, give us a just idea of the structure of the epidermis, and of the disposition of its small laminæ that are laid over each other on a part of their surface, &c.

Vegetable life, justly, says the same author, compared in its resources and effects with animal life, would throw very great light on several phenomena, which, at present, it is difficult for us to conceive and to explain.

The medical treatment of vegetables, which is almost entirely surgical, would be equally benefited by these researches.

Thus the wounds of vegetables, like those of the human body, are much less dangerous when their surface is smooth, than when their edges are rough, lacerated, or contused. Trees cut down with a saw bud with difficulty, whilst those felled with an axe vegetate more briskly.—The saw tears the vegetable structure and produces a greater or less alteration in organization. The unequal surface of a tree thus cut down retains humidity, as destructive to the trunk, of which it induces a rottenness, as too great a quantity of pus, that so habitually moistens the surface of an animal wound, destroys granulation and prevents cicatrization.

In considering the application, or rather the relation of physiology to philosophy in general, the philosophy of mind will be particularly dwelt upon.

In considering the application of physiology to the fine arts, the error in the construction of the antique statues, and of those of Michael Angelo, both with regard to the individual muscles supposed to be brought into action, and with regard to a hitherto unobserved principle of attitude, will be carefully pointed out.