CLASSIFICATION OF THE COLON-CLOACAE GROUP 263 



fcically always forms gas from sucrose, raffinose, mannitol and 

 salicin; and occasionally from dextrin; gelatin is typically liquefied; 

 and glycerol, inulin and starch are not fermented. As noted 

 above, the few glycerol, inulin and starch fermenters are probably 

 due to mixed cultures and may be dismissed. 



The three sucrose negative cultures (also raffinose negative) 

 may be regarded as a variety corresponding to the B. levans 

 which MacConkey records as very rare. 



The dextrin fermenters probably also constitute a variety of 

 B. cloacae but as the composition of dextrin is so variable we 

 hesitate to employ it for differential purposes for the present. 



B. aerogenes resembles B. cloacae in several respects. It forms 

 acetylmethylcarbinol from glucose; is alkaline to methyl-red; 

 and ferments sucrose, raffinose, mannitol, and salicin with gas for- 

 mation. On the other hand lactose is more vigorously attacked; 

 gelatin is typically not liquefied; the organisms are non-motile; 

 while glycerol and starch are fermented with gas formation. 



Indol was formed by 31 (50 per cent); gas from dulcitol was 

 formed by 31 (50 per cent) ; and from inulin by 18 (33f per cent) 

 of the B. aerogenes strains (8 cultures were not tested with inulin) . 

 From tables 2 and 2a which show the distribution with respect t o 

 indol, inulin and dulcitol, and the correlation coefficients for these 

 reactions, it is evident that the characters are not associated. 

 They may be of significance for separation of varieties. The 

 utter lack of correlation necessitates the employment of all of 

 these characters, which would lead to the formation of eight 

 varieties. It is deemed unwise to establish such varieties until 

 more extensive collections are studied. 



THE COLI GROUP 



In the B. colt group are included 182 strains quite evenly dis- 

 tributed between the different animal sources, sewage and soil. 

 The group differs sharply from the B. aerogenes-B. cloacae series 

 in that the Voges-Proskauer reaction is negative and the methyl- 

 red reaction positive. Starch is not attacked by any of the 

 strains. It has been shown by the author that the Voges-Pros- 



