Page:Physiological Researches upon Life and Death.djvu/25

Rh thing more is necessary than to display upon this canvas the external organs proper to establish its different relations.

It hence results that the functions of the animal form two very distinct classes. The one is composed of a continual succession of assimilation and excretion; by these it is incessantly converting to its own substance the particles of surrounding bodies, and again ejecting these particles when they have become heterogeneous. It lives within itself only, by this class of functions; by the other, it exists, as it were, out of itself: it is the inhabitant of the world, and not, like the vegetable, of the spot which gave it birth. It feels and perceives what surrounds it, reflects its sensations, moves voluntarily according to their influence, and most generally has the power of communicating by voice, its desires and its fears, its pleasures or its pains.

The assemblage of the functions of the first class, I call organic life, because all organized beings, vegetable or animal, enjoy it in a greater or less degree, and because organic texture is the only condition necessary to its exercise. The united functions of the second class form animal life, thus called, because it is the exclusive attribute of the animal kingdom.

Generation does not enter into the series of phenomena of these two lives, they having relation to the individual, while that regards the species only: nor is it connected, except indirectly, to most of the other functions. It begins its exercise only after the others have been long in action, and is extinct long before they cease to act. In the greater part of animals its periods of activity are separated by long intervals of rest; in man, in whom its remissions are less durable, its relations to the functions are not more numerous. The subtraction of those organs which are its agents, is almost always followed by a general increase of nutri-