VIBRIO CHOLERM 523 



vibrio is not, except occasionally in large doses (Wherry 1905). Pigeons injected 

 intramuscularly with | agar culture of V . metchnikovi die in about 8 hours with 

 general septicaemia (MetchnikofE 1893). Intratracheal injection appears to be even 

 more fatal, since not only guinea-pigs, pigeons, and fowls, but also rabbits may be 

 infected by this route (Gamaleia 18886). Deneke's Vibrio tyrogenus is pathogenic 

 for the guinea-pig and the pigeon. Half an agar culture injected intraperitoneally 

 into a guinea-pig was fatal in 6 hours, and a whole agar culture injected intra- 

 muscularly into a pigeon was fatal in 7 hours (Metchnikoff 1893). Finkler-Prior's 

 Vibrio proteus resembles V. tyrogenus, but is slightly less virulent. 



V. phosphor escens is pathogenic for guinea-pigs, rabbits, and pigeons. About 

 500 million organisms injected intraperitoneally into guinea-pigs, intravenously into 

 rabbits, or intramuscularly into pigeons proved fatal in 24 hours ; vibrios were 

 isolated post mortem from the heart's blood of the pigeons (Jermoljewa 1926). If a 

 guinea-pig that has died after intraperitoneal injection is opened up and placed in 

 the dark, the viscera are seen to exhibit a marked phosphorescence (Kutscher 

 1893). 



Most other members of the group are non-pathogenic. The virulence of V . 

 cholerw is variable. Freshly isolated strains are more virulent than those kept in 

 the laboratory. Moreover, even on isolation, the virulence of different strains to 

 laboratory animals appears to vary. Haffkine (1892) stated that it was possible 

 to raise the virulence by passing the organisms through the peritoneal cavity of 

 guinea-pigs ; between each injection the peritoneal exudate was exposed to the 

 air for some time at room temperature. By growing the vibrio in broth in a con- 

 stantly aerated atmosphere and subculturing every 2 or 3 days, the virulence was 

 said to diminish. Gotschlich and Weigang (1895) also stated that the virulence 

 might be raised by intraperitoneal passage through guinea-pigs. 



Variation. — The occurrence of smooth, rough and rugose forms of the cholera 

 vibrio has already been referred to in the sections on cultural and antigenic char- 

 acters. Confusion has arisen from paying too much attention to colonial variation 

 without a full study of antigenic and other properties. As White (1938) points 

 out, the essential feature of rough variants is their absence of the specific smooth 

 polysaccharide. 



There is a widespread belief that cholera vibrios under unfavourable conditions, 

 such as in water, may lose their specific characters and be transformed into some 

 other type of vibrio. The alleged transmutation of vibrios in the laboratory by 

 Linton (1935), Linton, Shrivastava, and Mitra (1934-35), Linton, Seal and Mitra 

 (1938), and Taylor and Ahuja (1935-36) has tended to strengthen this belief. 

 White (1937«), who has studied some of the strains before and after their alleged 

 change, can find no evidence to support the conception of vibrionic transmutabiUty. 

 Until further studies have been made it is probably wiser to adopt a strictly con- 

 servative attitude toward the limits of variation within the different species of 

 this group. 



We append a summarized description of V. cholerce, and brief notes on the 

 characters of other species which have been described and named. (For general 

 classification of members of this group, see Heiberg 1935.) 



Vibrio cholerse 



Synonym. — Comma bacillus. 



Isolation.—Koch. in 1884 (1886). 



Habitat. — Intestinal contents of cholera patients and carriers. 



