ALIMENTARY ENERGETICS. 121 



chemistry from the time of Lavoisier down to our own 

 day has been to teach us that tlie antecedent of the 

 vital phenomenon is always a cJumical pJienomenon. 

 The vital energies are derived from the potential 

 chemical energy accumulated in the immediate con- 

 stituent principles of the organism. In the same way 

 tfu consequent pJienomenon of tJte vital pJienomenon is in 

 general a tliermal phenomenon. The final form of 

 vital energy is thermal energy. These three assertions 

 as to the nature, the origin, and the final form of vital 

 phenomena constitute the three fundamental prin- 

 ciples, the three laws, of biological energetics. 



Food, a Source of Heat. It is not qua source of Jieat 

 tttatfood is the source of vital energy. The place of 

 vital energy in the cycle of universal energy is com- 

 pletely determined. It lies between the chemical 

 energy which is its generating form and the thermal 

 energy which is its form of disappearance, of break- 

 down, the "degraded form," as the physicists say. 

 Hence we have a result which can be immediately 

 applied in the theory of food namely, that heat is in 

 the dynamical order an excretum of the animal life 

 rejected by the living being, just as in the substantial 

 order, urea, carbonic acid and water, are the materials 

 used up and again rejected by it We therefore must 

 not think of the transformation in the animal organ- 

 ism of heat into vital energy, as certain physiologists 

 always do. Nor must we think, with Beclard, of its 

 transformation into muscular movement ; or, as others 

 have maintained, into animal electricity. This is not 

 only an error of doctrine but an error of fact It 

 proceeds from a false interpretation of the principle of 

 the mechanical equivalent of heat and a misunder- 

 standing of Carnot's principle. Thermal energy does 



