384 CHOLERA. 



follow in nature, as any particular saprophytic organism 

 requires a special habitat that is, certain suitable conditions 

 for its growth in competition with other organisms. Though 

 we can state generally that the conditions favourable for the 

 growth of the cholera spirillum are, a warm temperature, 

 moisture, a good supply of oxygen, and a considerable 

 proportion of organic material, we do not know the exact 

 circumstances under which it can flourish for an 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 



