ENERGY IX BIOLOGY. 99 



I will therefore grant, as a provisional postulate, 

 the consequences of which will have to be ultimately 

 justified, that the Hying 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: TIic pJienomena of life have 

 t/ie same claim to be energetic metamorphoses as t/u 

 other phenomena of nature. 



This postulate is the foundation of biological 

 energetics. It may be useful to give some ex- 

 planation relative to the signification, the origin, and 

 the scope of this statement. 



Biological energetics is nothing but general physi- 

 ology 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." 



i. ENERGY AT PLAY IN LIVING BEINGS. 

 COMMON OR PHYSICAL ENERGIES. VITAL 

 ENERGIES. 



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, 



