possessing a single polar flagellum. Gram- negative. Gelatin colonies: Small, yellowish white. Gelatin stab: Rapid, napiform liquefac- tion. Agar colonies: Circular, whitish brown, moist, glistening, translucent, slightlj^ raised, entire. Agar slant: Brownish gray, moist, glisten- ing. McConkey's medium: Good growth, colonies colorless when young, soon pinkish, medium becomes darker red. Broth: Slightly turbid, with fragile, wrinkled pellicle and flocculent precipitate. Peptone water: Characteristic rapid growth, chiefly at surface, where, after 6 to 9 hours, a delicate membrane is formed; little turbidity, deposit apparently derived from pellicle (Topley and Wilson, Princip. Bact. and Immun., 2nd ed., 1936, 388). Readily isolated from the surface film of 0.1 per cent peptone water. Litmus milk: Alkaline at the top and slightly acid at bottom; generally not coagulated; peptonized; reduced. Potato: Dirty white to yellowish, moist, glistening, spreading growth. Blood serum: Abundant growth, some- times slow liquefaction. Blood agar: The blood pigment is di- gested forming a greenish zone around colonies; a true soluble hemolysin is not formed (the El Tor vibrio also digests blood pigment but in addition produces a soluble hemolysin; otherwise it is said to be indistinguishable from the typical cholera vibrio) . Indole produced. Cholera-red reaction, which depends on production of indole and reduction of nitrates, is positive. Hydrogen sulfide produced. Acid but no gas from glucose, fructose, galactose, maltose, sucrose and mannitol. Slowly from glycerol. Does not attack lactose, inulin or dulcitol. Group I of Heiberg (Classification of Vibrio cholerae and Cholera-like Vibrios. Copenhagen, 1935) ferments mannose and sucrose but not arabinose. Hydrolyzes starch actively in alkaline media. Nitrites produced from nitrates. High alkali but low acid tolerance: optimum pH, between 7.6 and 8.0; for isolation on Dieudonne's medium, pH 9.0 to 9.6. Aerobic, grows best in abundant oxygen; under strict anaerobiosis may fail to grow altogether. Optimum temperature, 37° C. Maximum, 42° C. Minimum, 14° C. Source: Isolated from the intestinal contents of cholera patients in Egypt and India. Habitat: Found in the intestinal contents of cholera patients and carriers. The relationships existing among the cholerigenic and non-pathogenic water vibrios, although studied intensively, have not yet been completely defined. As a working scheme, based on somatic (O) and flagellar (H) antigen studies, Gardner and Vankatraman (Jour. Hyg., 35, 1935, 262- 282) suggest the one shown in the graph on the following page. Linton (Bact. Rev., 4, 1940, 275) has out- lined a classification of the vibrios based upon their protein and polysaccharide struc- tures. Using chemical methods, it was found that one polysaccharide and one protein was commonly obtained from each strain of vibrio; when exceptions occurred, it was invariably noted that the strain was under- going dissociation. Given a single protein and polysaccharide in each vibrio, it was possible to divide the strains into six groups, which were numbered in the order of their discovery as shown in the table. A chemical grouping of the cholerigenic and water vibrios. Group Protein Type Polysaccharide Type I I I II I II III II II IV II I V II III VI I III The strains of Groups I and II possess the same protein and different polysaccha-
