96 BACTERIOLOGY. 



COH, succinic acid and propionic acid are able 

 to yield this group only by oxidation, i. e., 

 CH 2 + O = CHOH. The former bodies are, 

 as a matter of fact, altogether better food-sub- 

 stances for bacteria than the latter, and, 

 furthermore, the former have nutritious value 

 under all conditions, and especially in anaero- 

 biosis, while the latter can be used for food 

 only in the presence of oxygen. As an ex- 

 ample of the utilization of such substances, 

 both in conditions of anaerobiosis and aerobio- 

 sis, tartaric acid may be instanced (cf. Low). 

 In the absence of oxygen : 



C 4 H 6 O 6 = 2CH 8 O + H 2 + 2CO 2 

 tartaric acid, formaldehyde, hydrogen, carbon dioxide. 



In the presence of oxygen : 



C 4 H 6 O 6 + O = 2CH 2 O + H 2 O + 2CO 2 



Nutritive value depends therefore upon 

 purely chemical properties, and I have here 

 indicated one aspect of the matter. Such 

 bodies as have little nutritive value can be 

 utilized only with the aid of oxygen because, 

 when they break up without oxygen, they can 

 afford neither the chemical components neces- 

 sary for the construction of protoplasm nor the 

 necessary energy for construction of proto- 

 plasm out of other substances. 



I have previously called attention to the 



