CHOLERA SPIRILLUM 257 



of the mucosa the organisms loosen the epithelial cells, which 

 are shed in flakes and give to the stools their characteristic rice- 

 water appearance. In the more chronic forms of the disease 

 extensive necrosis of the intestinal wall and the formation of a 

 false membrane may occur together with a considerable amount 

 of hemorrhage. It is generally thought that the organisms never 

 invade the blood stream and internal organs. 



The causal relation of the " comma bacillus " of Koch to Asiatic 

 cholera has been fully established by a number of laboratory 

 experiments and accidents. In 1884 a student in Koch's labor- 

 atory in Berlin suddenly developed a severe attack of cholera, 

 and infection could have come in no other way than through the 

 cholera cultures with which the man had been working. In another 

 German laboratory Pettenkoffer and Emmerich experimented 

 upon themselves by swallowing a small quantity of a fresh cholera 

 culture. Pettenkoffer developed a mild attack of the disease, but 

 Emmerich became seriously ill. In both cases numerous cholera 

 spirilla were found in the stools. Dr. Oergal, an assistant in the 

 Hamburg Hygienic Institute, became accidentally infected while 

 experimenting with the peritoneal fluid of an injected guinea pig. 

 After a few days he died of typical cholera, although there were 

 no other cases in the city at the time. 



On the other hand, many similar experimental cases have given 

 negative results. This, however, may be explained as due to differ- 

 ent degrees of susceptibility. The positive cases have been suffi- 

 ciently well marked to warrant the acceptance of the organism 

 as the causal agent of the disease. 



Immunity. One attack of cholera produces a moderate degree 

 of immunity of rather short duration. Prophylactic vaccination 

 affords a certain degree of protection in case of exposure to the 

 disease. 



Bacteriological Diagnosis. A stained film preparation or a 

 hanging drop is made from the feces and examined microscopically. 

 In some cases the spirilla are so numerous and present a picture 

 so unique that a microscopic examination is sufficient for diagnosis 

 during an epidemic. For the detection of carriers or in case of 



