18 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



nature. On account of the definiteness and impor- 

 tance of the evidence so obtainable I prefer to risk 

 the introduction of some unfamiliar facts rather than 

 the exclusion of highly significant evidence. 



The cells of the animal body are mainly nourished 

 by taking up three kinds of foodstuffs which are 

 widely different in their chemical character. These 

 foodstuffs are, first, the nitrogen-holding complex 

 compounds which we call proteins; second, fats; 

 and third, the carbohydrates. When acted on by 

 certain enzymes or ferments, the substances belong- 

 ing to these groups are split into somewhat smaller 

 molecules and take up the elements of water. This 

 process is known to chemists as hydrolysis, and the 

 products of the splitting are called hydrolytic prod- 

 ucts. Oxidation in the animal body relates mainly 

 to the hydrolytic products of the proteins, the fats, 

 and the carbohydrates. It is from the oxidation 

 of these substances that the living animal organism 

 derives most of its energy. 



How are theser various oxidations in the animal 

 body to be explained ? The remarkable thing about 

 them is that they go on so energetically at the low 

 temperature of the animal body. It is obvious to 

 anyone who thinks at all on the subject that the free 

 oxygen of the air does not oxidize any of the common 

 foodstuffs when these are exposed to its action. It 

 is true that there is some evidence that the fat 

 deposits of Egyptian mummies show a moderate 

 degree of oxidation, which can probably be attrib- 



