THE THEORY OF ENERGY AND THE LIVING WORLD. 535 



energy peculiar to vitality, or the liviug energy, M. Ohauveau calls 

 physiological work. This we here consider as exchangeable from the 

 point of view of equivalence with the energies of physics, just as these 

 are among themselves. This is the significance of the first law of 

 energetics. 



Energetics teaches us that if chemical energy is the generating form 

 productive of vital energy, heat energy is the form of ejection, or emunc- 

 tory form, which is spoken of as degraded by physicists. Heat is, in 

 the dynamical order, of the same category as urea, carbonic acid and 

 water, the excreta in the material order. It is, therefore, entirely 

 through a false interpretation of the principle of the mechanical equiva- 

 lence of heat, or in ignorance of Carnot's principle, that some physiolo- 

 gists still speak of the transformation of heat into motion, or into 

 electricity, in the animal organism. Heat transforms itself into nothing 

 in the animal organism; it is only dissipated. Its utility conies, not 

 from its energetic value, but from its function in promoting chemical 

 reactions, as has already been explained in speaking of the general 

 characteristics of chemical energy. 



The consequences of these clear and general principles of physiolog- 

 ical energetics are of the greatest importance from a practical as well 

 as from a theoretical point of view. 



First, they show clearly the rank of the phenomena of life in the 

 universe. They are necessary to the understanding of that beautiful 

 harmony between the animal and vegetable kingdoms which Priestly, 

 Ingenhousz, Senebier and the chemical school of the beginning of the 

 century had disclosed, and which Dumas has described with such 

 incomparable clearness and success. Energetics expresses the thing 

 thus: The animal world employs the energy which the vegetable world 

 accumulates. Energetics goes beyond the bounds of life and to the 

 midst of cosmos. It shows how the vegetable world itself draws its 

 activity from the radiant energy of the sun, and how the animal life 

 at last restores the heat thus dissipated. The harmony between these 

 two kingdoms extends throughout nature. It makes a closed system of 

 the whole universe. 



From a more restricted point of view, and considering only the domain 

 of animal physiology, the laws of energetics embrace the function and 

 general principles of alimentation. The aliment is essentially a source 

 of energy, and only in an accessory way a source of heat. Precisely 

 the contrary is usually taught in our medical colleges; and this error, 

 though perhaps of no importance from the point of view of practice, 

 is, on the other hand, highly important as a matter of doctrine. The 

 energy which the aliment brings to the animal is the potential chemical 

 energy which it possesses by virtue of its chemical complexity. It is 

 this requirement of substances far up in the scale of chemical complexity 

 which links the animal to the vegetable, the latter being alone capable 

 of producing these syntheses. The animal activity liberates a part of 



