412 CHOLERA. 



indefinite period of time as a saprophyte. The fact that 

 the area in which cholera is an endemic disease is so 

 restricted tends to show that the conditions for a prolonged 

 growth of the spirillum outside the body are not usually 

 supplied. Yet, on the other hand, there is no doubt that 

 in ordinary conditions it can live a sufficient time outside 

 the body and multiply to a sufficient extent, to explain all 

 the facts known with regard to the persistence and spread 

 of cholera epidemics. 



Numerous experiments show that the cholera organisms 

 are, as a rule, rapidly killed by drying, usually in two or 

 three minutes when the drying has been thorough, and it is 

 inferred from this that they cannot be carried in the living 

 condition for any great distance through the air, a con- 

 clusion which is well supported by observations on the 

 spread of the disease. Cholera is practically always trans- 

 mitted by means of water or food contaminated by the 

 organism, and there is no doubt that contamination of the 

 water supply by choleraic discharges is the chief means by 

 which- areas of population are rapidly infected. It has 

 been shown that if flies are fed on material containing 

 cholera organisms, the organisms may be found alive within 

 their bodies twenty -four hours afterwards. And further, 

 Haffkine found that sterilised milk might become con- 

 taminated with cholera organisms, if kept in open jars to 

 which flies had free access, in a locality infected by cholera. 

 It is quite possible that infection may be carried by this 

 method in some cases. 



Experimental Inoculation. In considering the effects of 

 inoculation with the cholera organism, we are met with the 

 difficulty that none of the lower animals, so far as is known, 

 suffer from the disease under natural conditions. Even in 

 places where cholera is endemic, no corresponding affection 

 has been observed in any animals. And further, before the 

 discovery of the cholera organism, various efforts had been 

 made to induce the disease in animals by feeding them 

 with cholera dejecta, but without success. It is therefore 

 not surprising that the earlier experiments on animals by 



