PATHOGENIC SPIRILLA. 513 



with the cultures of the spirillum, but pigeons resist infection in this way. 

 Guinea-pigs usually die in from twenty to twenty-four hours after receiving 

 a subcutaneous inoculation ; at the autopsy an extensive subcutaneous 

 oedema is found in the vicinity of the point of inoculation, and a superficial 

 necrosis may be observed ; the blood and the organs generally contain the 

 4 ' vibrio " in great numbers, showing that the animals die from general in- 

 fection acute septicaemia. When infection occurs in these animals by way 

 of the stomach the intestine will be found highly inflamed and its liquid con- 

 tents will contain numerous spirilla. 



Gameleia has shown that pigeons and guinea-pigs may be made immune 

 by inoculating L them with sterilized cultures of the spirillum sterilized by 

 heat at 100 C. ^Old cultures contain more of the toxic substance than those 

 of recent date. Thus two to three cubic centimetres of a culture twenty days 

 old will kill a guinea-pig when injected subcutaneously, while five cubic 

 centimetres of a culture five days old usually fail to do so. According to 

 Pfeiffer, old cultures have a decidedly alkaline reaction, and their toxic power 

 is neutralized by the addition of sulphuric acid. 



Gameleia has claimed that by passing the cholera spirillum of Koch 

 through a series of pigeons, by successive inoculation, its pathogenic power 

 is greatly increased, and that when sterilized cultures of this virulent vari- 

 ety of the ' ' comma bacillus " are injected into pigeons they become immune 

 against the pathogenic action of the " vibrio Metschnikoff, and the reverse. 

 Pfeiffer (1889), in an extended and carefully conducted research, was not 

 able to obtain any evidence in support of this claim. 



