236 NUTRITION AND METABOLISM 



proportion of products quite different from the one suggested by the 

 equation. Recently Kamm has shown that a good mineral food 

 (probably phosphates are the essential agent) favors a formation of 

 gas and of volatile acids, while a scant supply of minerals causes the 

 bacteria to produce mainly lactic acid. We must assume, therefore, 

 at least two simultaneous independent fermentations: 



C 6 Hi 2 O 6 = 2C 3 H 6 O 3 

 and 



C 6 H 12 O 6 + H 2 O = CH 3 CO 2 H -f- CH 3 CH 2 OH + 2 CO 2 + 2 H 2 



The first equation is already known to us; it is the true lactic fermenta- 

 tion. The second equation may be divided still further into several 

 simpler equations. 



B. typhosus, causing typhoid fever, is closely related to B. coli, but 

 does not form gas. It forms, however, formic acid, HC0 2 H, which, if 

 decomposed, would give H 2 + C0 2 . 



The last type of sugar fermentations is the butyric fermentation, 

 in which butyric acid is the most conspicuous, but not the only fermen- 

 tation product. Acetic acid, hydrogen and carbon dioxide, and, with 

 some organisms at least, ethyl and butyl alcohols are formed along with 

 butyric acid. As already mentioned in the paragraph on the equation of 

 fermentation, Kruse believes this fermentation to consist of several 

 simultaneous fermentations, of which the most interesting at this stage 

 is the one showing the formation of butyric acid. 



C 6 H 12 6 = 2H 2 + 2 C0 2 + C 4 H 8 2 



The organisms producing butyric acid are mostly strictly anaerobic 

 spore formers with a tendency to form spindle-shaped cells; they stain 

 bluish-black with iodine and Bredemann gave the clostridium group 

 one species name, B. amylobacter, as he found no distinct and char- 

 acteristic differences between the many strains which he studied. 

 Many members of this group have the ability to fix nitrogen, i.e. 

 to build up their protoplasm without using any sources of nitrogen 

 other than nitrogen gas. Most of the so-called "Clostridium" species 

 belong in this group. Butyric acid is also formed by B. tetani and by 

 B. botulinus, the latter of which causes the most dangerous kind of meat 

 poisoning. 



Of other sugar fermentations may be mentioned here only by name, 



