NUTRITION. 215 



logical work. The excreta bear witness to a certain 

 organic demolition. Generalizing this teaching of 

 experiment the illustrious biologist divined the 

 fundamental law of energetics before the idea of 

 energetics had made much way in France. Every 

 act which expends energy, which produces heat or 

 motion, any manifestation whatever that may be 

 looked upon as an energetic transformation, neces- 

 sarily expends energy, and that energy is borrowed 

 from the substance of the organism. These sub- 

 stances are simplified, broken up, and destroyed. 

 Now the functional activity of the muscle produces 

 heat and movement in warm-blooded as well as in 

 cold-blooded animals. The functional activity of 

 the glands produces heat, as has. been shown by the 

 celebrated experiments of C. Ludwig on the salivary 

 secretion, and as is also shown by the study of thermal 

 topography in the vertebrates. The functional activity 

 of the nerves and the brain produces a slight quantity 

 of electricity and heat, as most observers have agreed. 

 The functional activity of the electrical and of the 

 photic apparatus also expends energy. Finally, the 

 eye which receives the photic impression destroys the 

 purple matter of the retina, and that purple matter, 

 as we well know, is recuperated in the dark during 

 the repose of the organ. Everything that is expressed 

 objectively, everything that is a phenomenon in the 

 living being — with the exception of growth and 

 formation, which are generally slow phenomena, and 

 of which we can only get an idea by the comparison 

 of successive states — all these energetic manifestations 

 suppose a destruction of organic matter, a chemical 

 simplification, the source of the energy manifested. 

 And that is why material destruction does not merely 



15 



