Page:Life and death (1911).djvu/113

 I will therefore grant, as a provisional postulate, the consequences of which will have to be ultimately justified, that the living and inanimate world alike show us nothing but transformations of matter and transformations of energy. The word phenomenon will have no other signification, whatever be the circumstances under which the phenomenon occurs. The varied manifestations which translate the activity of living beings thus correspond to transformations of energy, to conversions of one form into another, in conformity with the rules of equivalence laid down by the physicists. This conception may be formulated in the following manner:—The phenomena of life have the same claim to be energetic metamorphoses as the other phenomena of nature.

This postulate is the foundation of biological energetics. It may be useful to give some explanation relative to the signification, the origin, and the scope of this statement.

Biological energetics is nothing but general physiology reduced to the principles that are common to all the physical sciences. Robert Mayer and Helmholtz gave the best description of this science, and laid down its limits by defining it as "the study of the phenomena of life regarded from the point of view of energy."

§ 1.

Our first object will be to define and to enumerate the energies at play in living beings; to determine their more or less easy transformations from one to another,