v.] VARIOUS SPECIES OF COMMA-BACILLI. 107 



As has been stated in the foregoing pages, the comma- 

 bacilli found by Koch in Asiatic cholera have certain 

 definite characters in culture media (particularly in nutritive 

 gelatine) by which they can be easily distinguished from 

 other species, although not from all. Certain other 

 characters at first attributed to them are not exclusive. 



In his first publications Koch gave us to understand that 

 a notable character of the choleraic comma-bacilli is that 

 they require for good growth an alkaline medium. Now this 

 of course cannot and does not mean that they alone require 

 for good growth an alkaline medium, or that they do not 

 grow well in any but an alkaline medium. In the first place, 

 all the different species of comma-bacilli described in pre- 

 vious pages, and other species of bacteria also (various 

 micrococci and bacilli), grow very luxuriantly in an alkaline 

 medium, some much more luxuriantly in alkaline than in 

 neutral or faintly acid media. In the second place the 

 comma-bacilli of Asiatic cholera live and grow well also in 

 neutral and even faintly acid media. Thus the rice-water 

 stools and the intestinal contents have been in several in- 

 stances tested as to their reaction, and have been found of 

 neutral, or when kept for several hours, even of faintly acid 

 reaction, and nevertheless there were present in them 

 numerous comma-bacilli in active motion and multiplying 

 rapidly. I have repeatedly grown the choleraic comma- 

 bacilli in neutral nutritive gelatine, in neutral Agar-agar 

 mixture, and in neutral broth, and have thus obtained good 

 and active cultures. Koch has shown that notwithstanding 

 that the reaction of potato is acid, the comma-bacilli of 

 cholera grow well on it. 1 Culture media (gelatine broth, 

 broth peptone), though at starting faintly alkaline, become, 

 when choleraic comma-bacilli grow in them, faintly but 

 1 Loc. cit. pp. 1 8, 19, and 20. 



