148 ESSENTIALS OF BACTERIOLOGY 



garis in that the gelatin is less rapidly liquefied. Found also 

 in putrid material. 



Proteus Zenkeri (Hauser). Does not liquefy gelatin; 

 otherwise similar to the other two. 



CHAPTER XXI 

 CHOLERA BACTERIA 



Spirillum Choleras (Koch) (Comma Bacillus of Chol- 

 era) . Synonym, Vibrio Cholera. Origin. Koch, as a mem- 

 ber of the German expedition sent to India in 1883 to 

 study cholera, found this micro- 

 organism in the intestinal contents 

 of cholera patients, and by further 

 experiments identified it with the 

 disease. 



Form. The spirillum as seen or- 

 dinarily appears as a short, arc-like 

 body, about half the size of a tuber- 

 Fig. 64. Comma bacillus, cle bacillus, but when seen in large 

 pure culture (x 600). groups, spirals are formed, each little 

 arc appearing then as but a segment, 



a vibrio. Each arc is about three times as long as it is broad, 

 and possesses a flagellum at one end. Old agar cultures show 

 straight forms; S-shaped forms not uncommon, made of two 

 vibrios end to end (Fig. 64). 



Properties. The spirilla are very motile; liquefy gelatin. 

 They are easily affected by heat and dryness. Spores have 

 not been found. 



Growth. At ordinary temperatures on all nutrient media 



that have an alkaline or neutral reaction. Strongly aerobic. 



Colonies, Gelatin. After tw r enty-four hours, small white 



points w r hich gradually come to the surface, the gelatin being 



