EXPERIMENTAL INOCULATION 467 



perimental work. We shall give^ a short account of such 

 experiments : 



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. These experiments were confirmed by other observers, in- 

 cluding Koch. Thinking that probably the spirillum, when introduced 

 by the mouth, is 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 

 some time afterwards introduced a pure culture into the stomach by 

 means of a tube. As this method failed to give positive results, he tried 

 the effect of artificially interfering with the intestinal peristalsis by inject- 

 ing tincture of opium into the peritoneum (1 c.c. per 200 grm. weight), 

 in addition to neutralising as before with the carbonate of sodium solution. 

 The result was remarkable, as thirty out of thirty-five animals treated 

 died with symptoms of general prostration and collapse. Death occurs 

 after a few hours. Post mortem the small intestine is distended, its 

 mucous membrane congested, and it contains a colourless fluid with small 

 flocculi and the cholera organisms in practically pure cultures. Koch, 

 however, found that when the spirilla of Finkler and Prior, of Deneke, 

 and of Miller (vide infra) were employed by the same method, a certain, 

 though much smaller, proportion of the animals died from an intestinal 

 infection. Though the changes in these cases were not so characteristic, 

 they were sufficient to prevent the results obtained with the cholera 

 organism from being used as a demonstration of the specific relation of 

 the latter to the disease. 



Some additional facts with regard to choleraic infection of animals may 

 be mentioned. For example, Sabolotny found that in the marmot an 

 intestinal infection readily takes place by simple feeding with the 

 organism, there resulting the usual intestinal changes, sometimes with 

 hamiorrhagic peritonitis the organisms, however, being present also in 

 the blood. And of special interest is the fact, discovered by Metchnikoff, 

 that in the case of young rabbits shortly after birth a large proportion 

 die of choleraic infection when the organisms are simply introduced 

 along with the milk, as may be done by infecting the teats of the mother. 

 Further, from these animals thus infected the disease may be transmitted 

 to others by a natural mode of infection. In this affection of young 

 rabbits many of the symptoms of cholera are present. Many of these 

 experiments were performed with the vibrio of Massowah, which is now 

 admitted not to be a true cholera organism, others with a cholera vibrio 

 obtained from the water of the Seine. 



It will be seen from the above account that the evidence 

 obtained from experiments on intestinal infection of animals, 

 though by no means sufficient to establish the specific relation- 

 ship of the cholera organism, is on the whole favourable to this 

 view, especially when it is borne in mind that animals do not in 

 natural conditions suffer from the disease. 



Experiments performed by direct inoculation also supply 

 interesting facts. Intraperitoneal injection in guinea-pigs is 



