438 MICRO-ORGANISMS AND DISEASE [chap. 



reached the intestinal canal. . . . The comma bacilli had 

 been destroyed in the stomachs of these animals. . . The 

 experiment was therefore modified by introducing the sub- 

 stances direct into the intestines of the animals. The belly 

 was opened, and the liquid was injected immediately into 

 the small intestine with a Pravaz syringe. The animals 

 bore this very well, but it did not make them ill. 

 We also tried to bring the cholera dejecta as high as 

 possible into the intestines of monkeys by means of a 

 long catheter. This succeeded very well, but the animals 

 did not suffer from it." "I must also mention," says 

 Koch, " that purgatives were previously administered to 

 the animals in order to put the intestine into a state of 

 irritation, and then the infecting substance was given, 

 without producing any different result. The only experi- 

 ment in which the comma bacilli exhibited a pathogenic 

 effect, which therefore gave me hope at first that we should 

 arrive at some result, was that in which pure cultivations 

 were injected directly into the blood-vessels of rabbits or 

 into the abdominal cavity of mice. Rabbits seemed very 

 ill after the injection, but recovered after a few days. Mice, 

 on the contrary, died from twenty-four to forty-eight hours 

 after the injection, and comma bacilli were found in their 

 blood. Of course they must be administered to the animals 

 in large quantities ; and it is not the same as in other ex- 

 periments connected with infection, where the smallest 

 quantities of infectious matter are used, and yet an effect 

 is produced. In order to arrive at certainty as to whether 

 animals can be affected with cholera, I made inquiries every- 

 where in India as to whether similar diseases had ever been 

 remarked amongst animals. In Bengal I was assured such 

 a phenomenon had never occurred. This province is ex- 

 tremely thickly populated, and there are many kinds of 



