348 SPECIFIC MICRO-ORGANISMS 



per 200 grams of body weight, injected into the peritoneal cavity. 

 In this way .a condition resembling cholera in man was induced, 

 and the animal died in 24 to 36 hours. Autopsy revealed severe 

 enteritis, and abundant cholera spirilla in the intestine. Similar 

 results may be obtained, however, when other organisms are 

 substituted for the cholera germs in this procedure. Intravenous 

 injection of cultures into rabbits, and feeding of virulent cultures 

 to very young rabbits gives rise to rather typical cholera in many 

 of the animals. Intraperitoneal injection of cultures into guinea- 

 pigs gives rise to fatal peritonitis. Pigeons are relatively immune. 



The poisons of the cholera germ are intimately connected 

 with the substance of the living cell. Culture filtrates are 

 slightly or not at all poisonous. The dead bacterial cells are 

 poisonous, but the poison in them is a very labile substance and 

 readily altered by heat. It seems to become soluble when the 

 cell disintegrates, and this may explain the poisonous properties 

 sometimes observed in the nitrates of older cultures. 



Immunity to this organism was obtained by Pfeiffer by inject- 

 ing non-fatal doses into guinea-pigs. When a small amount of 

 culture is injected into the peritoneal cavity of such an immune 

 animal, the bacteria become quickly clumped together and are 

 then rapidly disintegrated and dissolved in the peritoneal fluid. 

 This is known as Pfeiffer's phenomenon and was the first example 

 of cytolysis to be observed. The solution of the bacteria sets 

 free their poison and if a very large dose has been injected the 

 animal may be killed by this poison regardless of his immunity 

 to the living germs. 



Asiatic cholera seems to have existed in India for many 

 centuries and there are reliable records of its occurrence there 

 in the sixteenth, seventeenth and eighteenth centuries. The 

 first recognized great world invasion of cholera began in 

 1817 and ended in 1823. Succeeding pandemics occurred in 

 1826-1837, 1846-1862, and 1864-1875. The fifth invasion began 

 in 1883 and ended shortly after the great outbreak at Hamburg 

 in 1892. The sixth epidemic began in 1902 and has involved 



