EXPERIMENTAL INOCULATION 453 



so restricted, tends to show that the conditions for a prolonged 

 UTO \\tli nf tin- spirillum outside the body are not usually supplied. 

 Yrt. on tin- other hand, there is no doubt that in ordinary 

 conditions it can live a sufficient time outside the body and 

 multiply t<> a sufficient extent to explain all the facts known 

 with regard to the persistence and spread of cholera epidemics. 

 During an epidemic at St. Petersburg the cholera organism 

 was cultivated from the stools of a considerable number of 

 people suffering^ f rom slight intestinal disturbance, and even 

 (piite healthy individuals. The latter may be regarded as 

 "cholera-carriers," but the organisms were obtained from them 

 over a comparatively short period of time, and it is unknown to 

 what extent they maintain and spread the infection. 



Cholera organisms are, as a rule, rapidly killed by being 

 thoroughly dried, and it is inferred from this that they cannot 

 be carried in the living condition for any great distance through 

 the air, a conclusion which is well supported by observations 

 on the spread of the disease. Cholera is practically always 

 transmitted 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 Hies 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 contaminated 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 agency 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. And, further, 

 attempts to produce the disease by feeding with cholera dejecta, 

 as well as with cultures, have been unsuccessful. As the 

 organisms are confined to the alimentary tract in the natural 

 disease, attempts to induce their multiplication within the 

 intestine of animals by artificially arranging favouring con- 

 ditions, have occupied a prominent place in the experimental 

 work. \Ve shall give a short account of such experiments : 



Xikati and Rietsch were the first to inject the organisms directly into 

 tin duodenum of dogs and rabbits, and they succeeded in producing, in 

 a considerable proportion of the animals, a choleraic condition of the 

 inti'.stine. These experiments were confirmed by other observers, in- 



