General Anatomy, Applied to Physiology and Medicine, Vol. 1 (of 3)

by Xavier Bichat

VIII. Remarks upon the classification of functions.

The plan that I have followed in this work, is not the most favourable to the study of the functions. Many of them, such as digestion, respiration, &c. would find no place here, because they do not belong especially to the simple systems, but to a combination of them, an union of many systems, and even of many organs. Thus what I have said upon the functions, is introduced only incidentally in this work, the particular object of which is the analysis of the different simple systems that form the compound organs. However, as some would wish to connect the different facts of physiology that it contains, with a physiological classification, I will now explain that which I have adopted in my course of lectures.

We know how different the kinds of classification are. The ancient division, into animal, vital, and natural functions, rests upon so weak a foundation, that a methodical superstructure could not be raised upon it. Vicq d'Azyr has substituted one for it which offers hardly any more advantages, as it separates phenomena that are connected, and changes into functions, properties, such as sensibility, irritability, &c. Since this author, others have made divisions which are not more methodical, and are equally removed from the natural arrangement of the phenomena of life.

I have endeavoured, as far as possible, in classing the functions, to follow the path marked out by nature herself. I have laid, in my work upon Life and Death, the foundations of this classification, which I pursued before I published this work. Aristotle, Buffon, &c. have seen in man two kinds of functions, one which connects him with external bodies, the other, which serves for his nourishment. Grimaud brought forward again this idea, which is as great as it is true, in his course of physiology and in his memoir upon nutrition; but by considering it in too general a manner, he did not analyze it with sufficient exactness, he ranked among the external functions, only sensation and motion, he did not describe the brain as the centre of these functions, nor place the voice among them, which is however one of the great means of communication, with the bodies that surround us. He did not analyze more accurately the internal functions. He did not point out their connexion in the elaboration of nutritive matter, where each works in its turn, if I may so express myself; nor show the distinctive characters, which separate generation from all the other functions relating to the individual alone. Besides, the distinction of internal and external functions was only presented as a general sketch in his Memoir upon Nutrition, and not as a means of classification. He did not avail himself of it, in the division of the functions, in his lectures, of which many manuscripts arranged by himself, are to be met with at the present time; in these he examined, 1st. osteogony, which was treated at much length; 2d. the action of the muscles; 3d. the action of the vessels or the circulation; 4th. generation; 5th. the action of the organs of the senses; 6th. the action of the brain and nerves; 7th. digestion; 8th. secretion; 9th. respiration, &c. From this it may be perceived, that Grimaud, like preceding authors, mixed together all the functions without referring them to certain general heads.

In reflecting upon the division pointed out above, I soon saw that it was not only one of those general views, one of those great outlines, that are oftentimes made by men of genius who cultivate physiology, but that it might become the permanent basis of a methodical classification. To come at this classification I observed that it was necessary at first to refer all the functions to two great classes, one relating to the individual, the other to the species; that these two classes had nothing in common, but the general connexion that unites all the phenomena of living bodies; but a variety of distinctive attributes characterize them, which cannot be separated from them.

These two first classes being rigorously defined, and their limits established by nature, I sought to discover in each, orders equally natural; this was easy in the functions relating to the individual. In fact, this was the place for the general outline of Aristotle and Buffon; but it was not to be presented in too general a manner; the nature and connexion of the functions peculiar to each order, were to be accurately assigned.

I called the order of functions that connects us with external bodies, animal life, thus indicating that this order belongs alone to animals, that it is more with them than with vegetables, and that it is the addition of these functions that particularly distinguishes them from vegetables. I called organic life, the order that serves for the constant composition and decomposition of our bodies, because this life is common to all organized beings, vegetables as well as animals; and because the only condition of enjoying it is organization; so that it forms a boundary between organic and inorganic bodies, as animal life serves to separate the two classes that form the first.

Animal life is composed of the action of the senses which receive impressions, of the brain which perceives them, reflects, and wills, of the voluntary muscles and larynx that execute this volition, and of the nerves which are the agents of transmission. The brain is truly the central organ of this life. Digestion, circulation, respiration, exhalation, absorption, secretion, nutrition, calorification, compose organic life, which has the heart for its principal and central organ.

I place calorification here, because it is evident from what I have said under the article upon the capillary systems, that it is a function analogous to secretion, exhalation and nutrition. It is truly a separation of combined caloric, from the mass of blood. It is, if the expression is preferred, a secretion or exhalation of that fluid in every part of the body. I have not even at present given this place to heat in my physiological classification: but in reflecting upon the method of its production, it will be seen that it ought to have it.

The two orders of the first class being established, it was easy to assign those of the second, which are three in number: 1st. functions belonging to the male; 2d. those belonging to the female; 3d. those arising from an union of the two sexes and the product of this union; these are the three orders.