54 MAN, — THE ANIMAL 



reality the Law of Metabolism, is through a study 

 of respiration. Respiration is clearly a vital 

 process that takes place within the living cells in 

 which oxygen reacts on carbon and energy, in the 

 form of heat, is supplied. Oxygen exists in the 

 atmosphere as Oo, molecular oxygen, and in very 

 small quantities as O3, ozone. When these two 

 chemical bodies are brought in contact with living 

 protoplasm, more heat is furnished by O3 than O2. 

 If this difference is computed, there are found to be 

 32,000 more energy units. (Calories.) At first 

 thought this seems to be a very great difference, 

 but if an equal amount of coal is burned with O2 

 and the same amount could be burned with O3, 

 there would result approximately 20 per cent more 

 heat. The percentage of difference is probably 

 much higher in living protoplasm but not as great 

 as one would infer from the figures 32,000. The 

 important fact to be remembered from this illus- 

 tration is that heat is constantly being given off 

 to our bodies as certain groups of molecules under- 

 go simplification. This is the source of the 

 energy, then, that furnishes heat to keep our bodies 

 going. 



The source of the energy for bodily movement, 

 growth and repair of tissues is to be found in the 

 inanimate food molecules which in turn derive 

 their energy from the process by which they are 

 manufactured. Food energy in its relation to 



