THE PHYSIOLOGY OF ALIMENTATION. 541 



and second, as a factor to promote chemical reactions. Its dissipation 

 then is not a pure loss. The author drew these conclusions some years 

 since from certain experiments on the alimentary value of alcohol, not 

 knowing that they had already been expressed by a contemporary 

 physiologist (A. Chauveau), and that they were already associated in his 

 mind with other conceptions of great interest, in the development of 

 which the author has since had the good fortune to assist. 



ii. 



To say that an aliment is a bearer of energy as well as matter is to 

 express in brief the fundamental idea of biology, by virtue of which 

 life is no longer thought of as creating any power special to itself. A 

 living being is looked upon as the scene of an incessant circulation of 

 matter and energy which comes from the exterior world and again 

 returns to it. Matter and energy together wholly constitute tbe aliment. 

 All its characteristics, the appreciation of its function, of its evolution, 

 and of the laws of alimentation, follow as the consequences of this 

 principle interpreted in the light of energetics. 



We first inquire what forms of energy are carried by the aliment. It 

 may be readily seen that there are at least two. For it is essentially 

 the source of chemical energy and secoudarily and in an accessory 

 manner a source of heat. Chemical energy alone, as we see from the 

 second law of energetics, is suitable for transportation into vital energy. 

 This is true at least for animals, but for plants it is otherwise. Their 

 vital cycle has neither the same point of departure nor destination, nor 

 does the transformation of energy here follow the same course. 



Again — and this is the third great law governing the phenomena — 

 the energy put in play in life is restored to the physical world in the 

 form of heat. We have remarked that the disengaged heat is employed 

 first to raise the internal temperature of the living being. This is the 

 animal warmth. 



There are therefore two kinds of energy furnished by the aliment; 

 but if it is wished to be very exact and to omit nothing it should be 

 added that they are not the only two but only the two principal and by 

 far the most important forms. It is not absolutely true that heat is the 

 only energy product of the vital cycle. This is the case only for the 

 animal in repose, when it contents itself with mere placid existence 

 without engaging in external mechanical work, such as raising external 

 weights, or even that of its own body. Mechanical work is then a sec- 

 ond possible termination of the vital energy cycle, but is not neces- 

 sarily so, for the motion and employment of force by animals are 

 subordinated to their volition. Again, the vital energy cycle may 

 terminate in the production of electricity, and such indeed is the case 

 with the operations of the nerves and muscles of all animals, and with 

 the operation of the special electric organ in certain fishes, such as the 



