Differences in Protein Compounds 179 



quite unlike in character. We know also that these 

 groups exist in cattle foods in unlike proportions. 

 For example, a much larger part of the protein of 

 roots consists of amides than is the case with the 

 grains, the protein of the latter being correspondingly 

 richer in albuminoids. If, therefore, albuminoids and 

 amides differ in function or value, we have established 

 one point of unlikeness between cornmeal and turnips. 

 The testimony so far obtained is quite consistent in 

 one direction, and indicates that the flesh -forming 

 function is confined to the true albuminoids. This 

 means that gelatin, amides (asparagin, etc.), extrac- 

 tives (creatin, etc.), cannot supply real muscle-build- 

 ing material. These non-proteids have nutritive value, 

 however. Experiments with gelatin and asparagin 

 have led to the conclusion that their presence in the 

 ration so protects the albuminoids from consumption 

 that the latter may have their maximum use as flesh- 

 and milk-formei's. The extractives seem to have a 

 peculiar place among the nutrients. They are not 

 regarded as flesh -formers, or as fuel, but so far as 

 is known they act merely as stimulants of the nervous 

 system. 



The albuminoids are the only flesh -formers. There 

 are, however, many albuminoids, and they differ among 

 themselves as raw material out of which to construct 

 the primary tissues of the animal body. Can albu- 

 mins do what globulins cannot ? Are nucleins su- 

 perior to albumins for special purposes f Not much 

 that is definite can be said on this point. Because 

 the various nitrogenous feeding stuffs are so generally 



