182 CLINICAL BACTERIOLOGY. 



The comma-bacillus does not possess spores. The arthro- 

 spore-formation that Hiippe assumed to exist as a result of 

 his earlier investigations has not been confirmed by other ob- 

 servers. 



The comma-bacilli are most readily stained with a saturated 

 aqueous solution of fuchsin or with carbolfuchsin. The expo- 

 sure to the stain should be longer than usual. The bacilli do 

 not stain by Gram's method. 



Cholera-bacteria grow upon all of the usual nutrient media, 

 and also in the absence of oxygen (facultative anaerobiosis), al- 

 though, according to recent investigations, it appears that oxygen 

 can never be entirely wanting. The cholera-bacilli always require 

 a distinctly alkaline nutrient medium for their development, as 

 they are exceedingly sensitive to the presence of even slight 



Fig. 49. Comma-bacilli (from the mouth) ; X 1000 (Giinther). 



amounts of acid. The degree of alkalinity most suitable for the 

 cultivation of cholera-bacilli is secured by adding one gram of 

 crystallized sodium carbonate to 100 cu. cm. of carefully neu- 

 tralized gelatin (Dahmen), or by preparing a 10.6 per cent, 

 solution of soda (from calcined sodium carbonate) and adding 

 55 cu. cm. of this to one liter of gelatin (Fliigge). For ordi- 

 nary purposes simple determination of the alkalinity by means 

 of litmus-paper is sufficient, but the paper must be made dis- 

 tinctly blue. 



The temperature-minimum for cholera-cultures is 8 C. 

 (46.4 F.) ; the temperature-optimum from 30 C. (86 F.) to 

 40 C. (104 F.). 



Appearances of Comma-bacilli in Cultures. Gelatin- 

 plates. The plates are best permitted to develop at 22 C. 



