ALIMENTARY ENERGETICS. 123 



It follows that heat intervenes in animal life in two 

 capacities — first and foremost as excretum, or end of 

 the vital phenomenon, of physiological work ; and on 

 the other hand, as a condition or primer o( the chemical 

 reactions of the organism ; and generally, as a favour- 

 able condition for the appearance of the physiological 

 manifestations of living matter. Thus, it is not 

 dissipated in sheer waste. 



I was led to adopt these views some years ago 

 from certain experiments on the role played in food by 

 alcohol. I did not then know that they had already 

 been expressed by one of the masters of contemporary 

 physiology, M. A. Chauveau, and that they were 

 related in his mind to a series of conceptions and of 

 researches of great interest, in the development of 

 which I have since then taken a share. 



Two Forms of Energy supplied to Animals by Food. 

 — To say that food is simultaneously a supply of 

 energy and a supply of matter, is really to express in 

 a single sentence the fundamental conception of 

 biology, in virtue of which life brings into play no 

 substratum or characteristic dynamism. According 

 to this, the living being appears to us as the 

 seat of an incessant circulation of matter and energy, 

 starting from the external world and returning 

 to it. All food is iiothing but this matter and this 

 energy. All its characteristics, our views as to its 

 role, its evolution, all the rules of alimentation are 

 simple consequences of this principle, interpreted by 

 the light of energetics. 



And first of all, let us ask what forms of energy are 

 afforded by food ? It is easy to see that there are 

 two — food is essentially a source of chemical energy ; 

 and secondarily and accessorily, it is a source of heat. 



