Page:Popular Science Monthly Volume 20.djvu/528

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HEN the science which endeavors to determine the phenomena of life and their connection was enabled to employ more exact expedients for its observations, the influence which the chemical process exerts on that of life became known. The physical apparatus of the body are preserved in the aggregate state and form, which are necessary for the performance of their functions by a definite chemical composition of the organs and the fluids which saturate them; and the source of the power required by the living body for its movements is to be sought for in the destruction of the compounds of which it is composed. This statement is not only justified by the axioms of science, but it is also confirmed by experience. For, even where the best methods of chemistry are deficient, we meet with phenomena, the appearance of which can only be explained by chemical decomposition. The substances of which the muscle is formed and the manner in which they are arranged are still imperfectly known; of the chemical process which takes place in the sarcous elements, when a muscle passes from rest to the contracted state, we know scarcely anything; still, we can not doubt for a moment that the muscle owes its form to its composition, and its motion to a change of the latter. This is shown by the fact that even by a slight change, which we may produce in the chemical constitution, though it be only a change in the amount of water or salt in the muscle, its elasticity, its sensibility, its ability to raise weights, is affected. By comparing the composition of the muscle, recovered after long repose, with that of the muscle tired by exertion, we immediately see that a change has taken place in it. The same may be said of the nerve, which has hitherto offered almost insurmountable obstacles to chemical examination; for how can its tiring be explained except by a chemical change of its mass? All doubt must here be removed on considering the electric change which accompanies every excitation of the nerve, for the differences in the electric tension, which appear in this momentary phenomenon, give distinct evidence of a chemical change.

For a complete understanding of these phenomena, an exact knowledge of the chemical processes in the organism is essential. At present we do not possess this; nevertheless, it is well worth the trouble to examine how far we have advanced in this direction; what requirements are to be fulfilled for further investigations; and in what