106 THE MECHANISM OF LIFE 



certain substances will determine the chemical transformations 

 of large quantities of matter, there being' no proportion 

 between the amount of the catalytic substance and of the 

 matter transformed. These phenomena are, however, only 

 particular cases of the general law of energetics that trans- 

 formation requires a stimulus. The catalyzer, or ferment, 

 does not contribute matter to the reaction, but only the 

 minimal energy necessary to liberate the chemical potential 

 energy stored in the fermenting substance. 



We must therefore add a third to the two laws of ener- 

 getics, Mayer's law of conservation, and t'arnot's law of fall of 

 potential. This third law is the law of stimulus, the necessity 

 of the intervention of an external excitatory force capable of 

 setting in motion the current of energy required for a trans- 

 formation. This stimulus is the primary phenomenon, the 

 determinant cause of such transformation. 



Three conditions, then, are required for a transformation or 

 displacement of energy : — 



1. The cause, the intervention of a stimulus which starts 

 the transformation or displacement. 



2. The possibility, the necessary fall of potential. 



.'3. The condition, the conservation of the energy con- 

 cerned, since being indestructible its total quantity cannot 

 alter. 



Every living being is a transformer of energy. The lower 

 animals and man himself receive from food and air the potential 

 energy which becomes actual under the process of oxvdation. 

 This chemical combustion is the source of all vital energy ; the 

 ancients aptly compared life to a flame, and Lavoisier has 

 shown that life, like the flame, is maintained by a process of 

 oxydation. The energy derived from food and air is restored 

 by the organism to the external world in the form of heat and 

 mechanical motion. The celebrated experiments of Atwater 

 show that there i^ an absolute equality between the energy 

 obtained from the oxydation of the various aliments and the 

 sum of the calorific and mechanical energy liberated by a living 

 being. 



Man obtains his supply of energy either directly from the 



