132 THE BACTERIA IN ASIATIC CHOLERA. [CH, 



observations, who could obtain some of his ptomaines only 

 from certain substances, not from others. 



Koch having very likely felt that experiments such as 

 those which he and van Ermengem made after the method 

 of Nicati and Rietsch were not free from objection, inasmuch 

 as they involved severe surgical operations (see p. 124), and 

 inasmuch as they, unlike all other experiments employed in 

 bacteriological research, did not imitate the methods of 

 infection as they occur under natural conditions, devised a 

 method of experiment which, though far removed from the 

 first, was not quite free of the second criticism. Starting 

 from the idea that the comma-bacilli are killed by the gastric 

 juice, and that in order to develop their pathogenic powers 

 they have to get unscathed and living into the small intestine 

 their natural breeding-ground it occurred to him that 

 this difficulty might be obviated by first neutralizing or 

 making alkaline the contents of the stomach, and then 

 introducing per os the comma-bacilli. He therefore kept 

 guinea-pigs for twenty-four hours without food, and injected 

 then into their stomach per os 5 ccm. of a five per cent, 

 watery solution of carbonate of sodium. This does not 

 noticeably injure the stomach, and, as direct observation 

 proved, kept the contents of the stomach in an alkaline 

 condition for three hours. Some minutes (twenty) after- 

 wards he introduced by catheter 10 ccm. of a cultivation of 

 the comma-bacilli in meat-infusion. 



The result is noteworthy. Seven guinea-pigs thus experi- 

 mented upon remained perfectly well ; " they were killed after 

 twenty hours, and the contents of their stomach, intestine, 

 and caecum, were examined by gelatine plate-cultivations. In 

 six of the seven animals, the cholera-bacteria could be de- 

 monstrated in the small intestine. The experiment had thus 

 in so far succeeded, that the cholera-bacilli had passed unin- 



