Detection of the Organism 615 



Specificity. The cholera spirillum is present in the de- 

 jecta of cholera with great regularity, and as regularly absent 

 from the dejecta of healthy individuals and those suffering 

 from other diseases. There is no satisfactory proof of the 

 specific nature of the organisms to be obtained by experi- 

 mentation upon animals. Animals are never affected by 

 any disease similar to cholera during epidemics, nor do foods 

 mixed with cholera discharges or with pure cultures of the 

 cholera spirillum affect them. Subcutaneous inoculations 

 do not produce cholera. 



Detection of the Organism. It often becomes a matter 

 of importance to detect the cholera spirilla in drinking- 

 water, and, as the number in which the bacteria exist in 

 such a liquid may be very small, difficulty may be experienced 

 in finding them by ordinary methods. One of the most 

 expeditious methods is that recommended by LofHer, who 

 adds 200 c.c. of the water to be examined to 10 c.c. of 

 bouillon, allows the mixture to stand in an incubator for 

 from twelve to twenty-four hours, and then makes plate 

 cultures from ^the superficial layer of the liquid, where, if 

 present, the development of the spirilla will be most rapid 

 because of the free access of air. 



Gordon * employs a medium composed of Lemco i gram, 

 peptone i gram, sodium bicarbonate o. i gram, starch i 

 gram, and distilled water 100 c.c. for the differentiation 

 of the cholera and Finkler-Prior spirilla. If the medium 

 be tinted with litmus and the cultures grown at 37 C., 

 a strongly acid change is produced by the true cholera 

 organism in twenty-four hours. The Finkler-Prior spirillum 

 produces but slight acidity, which first appears about the 

 third day. 



The identification of the cholera spirillum, and its differen- 

 tiation from spiral organisms of similar morphology obtained 

 from feces or water in which no cholera organisms are 

 expected, is becoming less and less easy as our knowledge 

 of the organisms increases. The following points may be 

 taken into consideration: (i) The typical morphology. 

 The true cholera organism is short, has a single curve, is 

 rounded at the ends, and possesses a single flagellum. (2) 

 The infectivity. Freshly isolated cultures should be patho- 

 genic for guinea-pigs and harmless to pigeons. (3) Vegeta- 



* "British Medical Journal," July 28, 1906. 



