EXPERIMENTAL INOCULATION. 385 



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 

 feeding them with pure cultures were attended with negative 

 results. As the organisms are confined to the alimentary 

 tract in the natural disease, attempts to induce their multi- 

 plication within the intestine of animals by artificially 

 arranging favouring conditions, have occupied a prominent 

 place in the experimental work. 



Nikati and Rietsch were the first to inject the organisms 

 directly into the duodenum of dogs and rabbits, and they 

 succeeded in producing, in a considerable proportion of 

 the animals, a choleraic condition of the intestine ; in their 

 earlier experiments the common bile duct was ligatured, but 

 the later were performed without this operation. These 

 experiments were confirmed by other observers, including 

 Koch. Thinking that probably the organisms, when in- 

 troduced by the mouth, are destroyed by the action of 

 the hydrochloric acid of the gastric secretion, Koch first 

 neutralised this acidity by administering to guinea-pigs 

 5 c.c. of a 5 per cent solution of carbonate of soda, and 

 sometime afterwards fed the animals with the organisms, or 

 introduced a fluid culture into the stomach by means of a 

 tube. Of nineteen animals treated in this way, only one 

 died with choleraic changes in the small intestine. This 

 animal had aborted a short time previously, and its ab- 

 dominal walls were very relaxed, and Koch considered that, 

 in some way at least, the intestinal peristalsis had been 

 interfered with, and thus opportunity had been afforded to 

 the organisms of gaining a foothold and multiplying in the 

 intestine. He accordingly tried the effect of artificially 

 interfering with the intestinal peristalsis by injecting tincture 

 of opium into the peritoneum (i c.c. per 200 grm. weight), 



2 5 



