CHOLERA BACILLUS 203 



stains it best. Occasionally involution forms are developed, 

 which do not stain well. So-called arthrospores are formed, ac- 

 cording to Hlippe. 



Habitat. It is said to exist constantly in the waters of the 

 Ganges in India. Is found in contaminated drinking water, 

 from rivers, lakes, and wells; also in human faeces, which, used as 

 manure, infests vegetables, and spreads the disease. It is found 

 in the intestines during cholera, and after death in other viscera. 

 It can be disseminated by convalescent or healthy carriers; 

 chronic carriers are not known. 



Vital Resistance. Is extremely sensitive to various deleterious 

 agencies. Minute quantities of mineral acids, and other chemical 

 disinfectants, as well as light, heat, and drying, quickly kill it; 

 i percent carbolic kills rapidly. A 1-2,000,000 solution of cor- 

 rosive sublimate destroys in from five to ten minutes. Its thermal 

 death-point is 6oC. for ten minutes (moist heat). 



Chemical Activities. It creates indol in large quantities, and 

 may be detected in peptone cultures merely by the addition of 

 sulphuric acid. Laevorotatory lactic acid is produced from all the 

 sugars. Gases are not formed. Yields alkali in culture; causes 

 slight coloration of potato, and produces a disagreeable odor in 

 bouillon; also yields H 2 S, and ferments that liquefy gelatine. 

 Bacteriolysins and invertin are also produced, as well as a toxin 

 which is soluble in water. The most powerful toxin, by far, is 

 contained in the cells of the vibrio themselves. This causes death 

 after intraperitoneal injection in guinea pigs. 



Oxygen Requirements. It is a facultative aerobe; its growth, 

 however, without oxygen is slow, while powerful toxins are 

 formed. 



Temperature. Grows best at 37C., but very well at 23C. 

 Does not grow below 8C. 



Cultures. On gelatine plates the growth is characteristic. 

 Small yellowish- white colonies, which rapidly liquefy the gelatine, 

 appear in twenty-four hours. As the colony increases in size it 



