Page:Physiological Researches upon Life and Death.djvu/27

Rh found, that the one which possesses the greatest share of sensibility, enjoys also the greatest variety of motions. The age of lively sensations, is that also of vivacity of motion; in sleep, when the first order is suspended, the second ceases, or is only irregularly exercised. Those blind of one eye, who only half see what surrounds them, connect their different motions with a tardiness and caution which would soon be lost, if their external communications were increased.

A double action is exercised also in organic life; the one is incessantly composing, while the other decomposes the animal. Such, in fact, (as the ancients and after them some moderns have observed) is his mode of existence, that what he was at one period he ceases to be at another; his organization remains the same, but his elements are continually changing. The nutritive particles alternately absorbed and ejected, pass from the animal to the plant, thence to the brute, and so on again to the animal.

Organic life is well suited to this continual circulation of matter. One order of functions assimilates to the animal, those substances which are to nourish him; another carries off, what has become heterogeneous to, after having for some time made a part of, his organisation.

The first, which is the order of assimilation, results from digestion, circulation, respiration, and nutrition. Every particle foreign to the body, before it can become one of its elements, receives the influence of these four functions.

When it has thus furnished its portion to the formation of our organs, absorption takes it up and conveys it into the circulatory stream, whence it is thrown out by pulmonary or cutaneous exhalation, and the various secretions by which all the fluids are ejected.

Absorption, circulation, exhalation, and secretion form then, the second order of functions of organic life, or the order of dis-assimilation.