322 PUBLIC HEALTH BACTERIOLOGY 



Staining. Readily with usual stains, best with Loeffler's 

 methylene-blue and weak carbol-fuchsin. Loses stain by 

 Gram's method. 



Resistance. Not great. Killed in ten minutes at 60 C. ; 

 on drying, in two hours. Mineral acids, i in 5000 to I in 

 10,000, destroy it in a few minutes. The gastric juice con- 

 tains 2 parts of HC1 per 1000 ; hence it is killed by gastric 

 juice, but can flourish in intestine. Freezing kills it in 

 three to four days. 



Agglutination Is shown by serum of cholera con- 

 valescents in dilutions of 1-15 to 1-120. Present eight to 

 ten days after attack, most marked twenty-eight days 

 after, and gradually diminishes. Has been noted as early 

 as first day of disease. 



Pathogenesis. For man : has been established by 

 laboratory accidents. Does not invade blood ; immense 

 numbers in stools ; in rice-water stools, loosened epithelial 

 cells loaded with vibrios. Not in urine. Infection by 

 mouth. Disappears from stools in two to three days. 

 Cholera carriers : healthy persons whose faeces contain 

 virulent cholera spirilla. Mostly spread by water, fomites, 

 fingers, flies. For animals : not established, though vibrios 

 on teats of suckling mother have infected young, with 

 choleraic symptoms. But as this result or similar ones have 

 been given by other vibrios, specificity cannot be founded 

 on this test. Intraperitoneal injection in guinea-pigs is 

 followed by general symptoms, with abdominal distension, 

 subnormal temperature, and profound collapse. There is 

 peritoneal effusion which may be almost clear, or with 

 flakes of lymph. There is little tendency to invade the 

 blood-stream, and the symptoms are mainly due to an 

 intoxication. It is not pathogenic to pigeons. 



Toxins. Filtered cholera cultures have as a rule little 

 toxic action ; hence it is inferred that little soluble toxin 

 is formed, but mostly endotoxin. Results at present are 

 conflicting. 



Pfeiffer's Reaction. If cholera spirilla are injected into 

 the peritoneum of an immunized guinea-pig, they first 

 lose their motility, then swell up and crumble into frag- 

 ments, which finally melt away and disappear. This 

 lysis is also manifested in a test tube in a mixture of serum 



