150 ESSENTIALS OF BACTERIOLOGY 



Potato. A yellow, honey-like, transparent layer if the 

 potato is kept at animal heat. 



Bouillon. A wrinkled scum is soon formed in bouillon. 

 The spirilla live well and grow in sterilized milk and sterilized 

 water, remaining virulent in the latter for many months. 



Fig. 66. Cholera Fig. 67. Cholera Fig. 68. Cholera 

 bacillus (forty-eight bacillus (sixty hours; -bacillus (seventy- 

 hours; 5 per cent. 5 per cent, gelatin). two hours; 15 per 

 gelatin). cent, gelatin). 



Figs. 66-68. Tube-cultures (from United States Government Report 

 on Cholera. Shakespeare). 



In ordinary water the bacteria present are destructive to the 

 comma bacilli, and they die in a few days. 



Dunham's Peptone Solution. Useful for the development of 

 nitrites and the indol reaction. (See p. 77.) Also for the 

 rapid development of the cholera vibrio. In four hours after 

 inoculation of peptone water pure cultures may be obtained; 



