102 UNIVERSITY OF WISCONSIN STUDIES 



B. coli is of a similar nature, but the primary and secondary 

 fermentations proceed at different rates and the end products 

 are different from those produced by B. acroyenes. (2) With 

 this are correlated various other characters, particularly a 

 higher percentage of indol formers in B. coli and the forma- 

 tion of acetyl-methyl-carbinol by B. aeroyenes. (3) There is 

 also correlated with these physiological differences a difference 

 in habitat. B. coli is the characteristic gas-forming organism 

 cf animal feces and is commonly found elsewhere only in 

 localities recently contaminated with fecal matter. B. aero- 

 cjenes and B. cloacae, on the other hand, occur rarely in bovine 

 feces and in relatively small numbers in human feces, but are 

 common in soil and materials contaminated with soil. 



B. coli is probably of specific rank and the subdivisions 

 usually made on the basis of saccharose fermentation should 

 not be looked upon as more than varieties of doubtful validity. 

 It is possible to make two similar varieties of B. aeroyeiws on 

 the basis of the fermentation of adonitol. This character is 

 given an added significance by a high correlation with habitat. 

 All of the aerogenes cultures from feces fermented adonitol 

 while a large percentage of those from grains were adonitol 

 negative. ;,': ; j- 



>a The distinction .between B. aeroyc tics and B, cloacae, beyond 

 tl^6 Ji(i\iefa^tkw*pl:' gelatin, is not very sharp, but everything 

 considered B. cloacae should be a separate species. 



A small group of cultures distinguished by the liquefaction 

 of gelatin, the fermentation of dextrose with the formation 

 of CO 2 only, and the fermentation of saccharose but usual 

 failure to ferment lactose is evidently identical with B. pro- 

 tens. The failure to ferment lactose, usually considered 

 the distinguishing character of B. proteus, does not coincide 

 perfectly with the more fundamental character indicated by 

 the single gaseous end product of the fermentation. The 

 unusual colony formation commonly looked upon as peculiar 

 to proteus is probably shared with some B. cloacae cultures. 

 A more logical separation between B. proteus and B. cloacae 

 would be on the end products of the fermentation rather than 

 on the nature of the material fermented. 



