VARIETIES OF COLON BACILLI 



189 



CHARACTERISTICS OF DEXTROSE FERMENTING BAC- 

 TERL\ FROM RAW, STORED, AND FILTERED WATERS 



(Houston, 191 i) 



The strains ha\'ing the combination of positive reac- 

 tions in lactose and peptone solution made up 53 per cent 

 of those isolated from the raw waters, 46 per cent of 

 those from the stored waters, and 34 per cent of those 

 from the stored and filtered waters. 



MacConkey's Classification of the Colon Group. 

 MacConkey is not satisfied with this general classifica- 

 tion of colon bacilli into typical and atypical forms, 

 but wishes to go much further, believing that even the 

 so-called " tj-pical B. coli " should rather be con- 

 sidered a complex including a considerable number of 

 definite individual tj-pes. After a detailed study of the 

 reactions of the lactose-fermenting bacteria of faeces 

 he outlined a new classification based on fermentative 

 reactions in the rarer sugars (MacConkey, 1905). 

 Using saccharose and-dulcite he fiirst divided the lactose- 

 fermenting organisms into four groups as indicated in 

 the table on p. 190. 



