ENERGY IN BIOLOGY. I05 



The laws of biological energetics are three in num- 

 ber. First of all, there is the fundamental principle 

 which we have just developed, and which is, so to 

 speak, laid down a pnori; and there are two other 

 principles, those established by experiment and 

 summing-up, as it were, the multitude of known 

 physiological effects. Of these two experimental 

 laws, one refers to the origin and the other to the 

 terviinatioti of the energies developed in living beings. 



§ 3. Second Law of Biological Energetics. • 



The Oigin of Vital Energy. — Vital energies have 

 their origin in one of the external or common energies 

 — not in any one we choose, as might be supposed, 

 but in one only: chemical energy. The third principle 

 will show us that they terminate in another energy or 

 a few others, also completely fixed. 



It follows that the phenomena of life must appear 

 to us to be a circulation of energy which, starting from 

 one fixed point in the physical world, returns to that 

 world by a few points, also fixed, after a transient 

 passage through the animal organism. 



Or more precisely, it is a transposition from the 

 realm of matter into the world of energy, of the idea 

 of the vital vortex of Cuvier and the biologists. 

 They defined life by its most constant property — 

 nutrition. Nutrition was exactly this current of 

 matter which the organism obtains from without by 

 alimentation, and which it throws out again by ex- 

 cretion ; and the even momentary interruption of 

 which, if complete, would be the signal of death. 

 The cycle of energy is the exact counterpart of 

 this cycle of matter. 



