492 THE CHOLERA VIBRIO 



in these the line of curvature is perpendicular to the surface of the slide : 

 the eye only sees the projection on the plane of the slide and the curve 

 vanishes. The vibrio is flagellated and is very motile. 



There are however varieties of the cholera vibrio which differ markedly from that 

 of Koch. Some are slender, irregularly- curved and occasionally have an elongated 

 S shape the Massaouah, Courbevoie and Paris vibrios. Others are straight 

 and never show any curve the Shanghai vibrio ; others again are very small and 

 of a cocco-bacillary form the Malta vibrio. Metchnikoff also noticed further 

 when sub-cultivating an old culture of the Angers vibrio in peptone water that it 

 had a slender elongated form, whereas ordinarily it was stumpy and curved. 



Involution forms occur in cultures several days old : many of the organisms 

 are irregularly swollen while others have the form of rounded bacilli of 

 variable size. 



FIG. 238. Vibrio cholerce (Massaouah strain). FIG. 239. Vibrio cholerce (Indian strain). 



Film from intestinal contents. Dilute carbol- Stained to show flagella. Nicoile's method, 



fuchsin. (Reich ; oc. II. ; obj. T Uh.) (Reich ; oc. IV. ; obj. T Uh.) 



According to Hueppe, some of these spherical bodies represent resistant 

 forms or arthrospores formed by encystment of the vibrios ; they are however 

 no more resistant to adverse influences than the vibrio itself. 



Staining reactions. The cholera vibrio is not so easily stained as most 

 pathogenic bacilli and rather strong staining solutions containing a mordant 

 should be used. Carbol-fuchsin diluted with 3 or 4 times its volume of water 

 is a very useful stain. The vibrios are gram-negative. 



Flagella. The number of flagella and their arrangement are very variable. 

 The typical cholera vibrio of Koch has one flagellum situated terminally 

 [monotrichous] : some varieties have two, three or even four terminally 

 situated flagella [lophotrichous] (Nicolle and Morax, Kolle, and Gotschlich). 

 The flagella may be stained in the living condition by Straus' method or, after 

 drying and fixing, by the methods described at p. 148 et seq. : it is necessary 

 always to use young agar cultures. 



2. Cultural characteristics. 



Conditions of growth. The cholera vibrio is essentially an aerobic organism : 

 a very scanty growth may however be obtained under anaerobic conditions 

 (Hueppe and Scholl). The organism grows at all temperatures between 

 12 and 40 C., the optimum being 37 C. It grows on all the ordinary 

 neutral or slightly alkaline media and ferments sugars. 



Characteristics of growth. Broth. Peptone water. When sown in these 

 media and incubated at 37 C. the cholera vibrio rapidly (6-10 hours) produces 

 a cloudiness of the medium, and later a thin whitish very delicate pellicle 

 forms on the surface of the liquid ; ultimately a flaky precipitate is deposited. 



