BACILLUS CO LI CO MM UN IS. 397 



should be important evidence of their separate individ- 

 uality. 



The author has no doubt that the Bacillus coli com- 

 munis is not a single species of bacteria, but is a name 

 applied to a group whose individual differences are thus 

 far too similar to enable us to differentiate them. This 

 opinion seems to be shared by other bacteriologists, some 

 of whom have attempted to separate the bacillus into 

 groups, types, or families. 



In order to establish a type species of the Bacillus coli 

 communis, Smith 1 says: 



* ' I would suggest that those forms be regarded as true 

 to this species which grow on gelatin in the form of deli- 

 cate, bluish, or more opaque, whitish expansions with 

 irregular margin, which are actively motile when exam- 

 ined in the hanging drop from young surface-colonies 

 taken from gelatin plates which coagulate milk within 

 a few days; grow upon potato, either as a rich-pale or 

 brownish-yellow deposit, or merely as a glistening, barely 

 recognizable layer, and which give a distinct indol reac- 

 tion. Their behavior in the fermentation-tube must 

 conform to the following scheme: 



"Variety a: 



"One per cent, dextrose-bouillon (at 37 C.). Total 

 gas approximately y 2 \ HCO 2 approximately ji\ reaction 

 strongly acid. 



"One per cent, lactose-bouillon: as in dextrose-bouil- 

 lon (with slight variations). 



"One per cent, saccharose-bouillon; gas-production 

 slower than the preceding, lasting from seven to four- 

 teen days. Total gas about % ; HCO 2 nearly %. The 

 final reaction in the bulb may be slightly acid or alkaline, 

 according to the rate of gas-production. 



"Variety /3: 



" The same in all respects, excepting as to its behavior 

 in saccharose-bouillon; neither gas nor acids are formed 

 in it." 



1 American Journal of the Medical Sciences, 1895, no, p. 287. 



