CHAPTER IV. 



CHARACTERS OF THE COMMA- BACILLI IN ARTIFICIAL 

 CULTIVATIONS. 



THE choleraic comma-bacilli possess in artificial media 

 certain well-established characters, by which they can be 

 readily recognised. Koch has clearly pointed out this fact, 

 and has minutely described the appearances. An idea seems 

 to have got abroad that while in India I denied this simple 

 truth. I said then that the choleraic comma-bacilli do not 

 differ in this matter of artificial cultivation from other septic 

 bacteria ; and I still say so now, after admitting and confirm- 

 ing the correctness of Koch's observations as to the behaviour 

 of the choleraic comma-bacilli in nutritive gelatine. No one 

 who has carefully followed recent research, and has suffi- 

 cient practical experience in the artificial cultivation of 

 bacteria, can for a moment doubt that the different bacteria, 

 be they septic or pathogenic, have morphological and cultural 

 characters of their own, which in some instances are more, 

 in others less, pronounced ; but a good many species are 

 known in which these differences in mode of growth are 

 sufficiently striking to be of diagnostic value even to the 

 unaided eye. Take, for instance, micrococci derived from 

 the air. There are a good many species of micrococci 



