SPIRILLUM CHOLERA 79 



isms already referred to. Many specimens of this 

 spirillum show, after long sub-culture, a great 

 tendency to form very flat spirals, and assume an 

 almost bacillary form. Klein has noted that there 

 appears to be some material present in the intestinal 

 secretions which gives the comma bacillus an in- 

 creased power of staining, so that the flagella may 

 be demonstrated in such preparations by simple 

 staining methods which would not succeed with 

 cultures in the usual media. The organism is 

 actively motile, and owes its motility to the pre- 

 sence of a flagellum situated at one pole as is seen 

 in the illustration (Fig. 78). 



The varieties of the cholera spirilla differ in the 

 number of flagella possessed by them though they 

 are always situated at the extremity of the cell and 

 do not usually exceed two or three. The young 

 short comma organisms are the most actively motile, 

 the spirilla forms being much less active, but not 

 entirely motionless. 



In some varieties (e.g., Massowah) they are absent 

 altogether. 



The culture on agar forms a rapidly growing, thin, 

 slightly iridescent film. The cultures on gelatine 

 have, from the first discovery, been regarded as the 

 most characteristic, and have been used to distinguish 



