244 INFECTIONS OF THE DIGESTIVE TRACT 



of introducing large numbers of B. coli communis, 

 proteus vulgaris of Hauser, and B. acidolactici into the 

 intestinal tract of dogs, with a view to determining the 

 effect upon indol production. It was found that the in- 

 jection of pure cultures of colon bacilli into the jeju- 

 num of dogs was followed by an increase in the indican 

 reaction of the urine and an increase in the output of the 

 ethereal sulphates. In order to exclude the introduction 

 of indol into the intestine in the course of these experi- 

 ments large numbers of colon bacilli were grown on agar- 

 plates and washed in salt solution. The introduction of 

 the living bacteria was followed by an increase in the 

 indican of the urine, whereas the introduction of sterile 

 cultures prepared in the same way showed at most only 

 a slight increase in the indican excretion. The inference 

 was drawn that the small amount of indol introduced in 

 feeding experiments made with colon bacilli does not 

 account for the marked increase in indican which was 

 noted in these experiments and that this increase is to 

 be attributed to the action of the colon bacilli themselves 

 growing upon a suitable medium. Similar experiments 

 were made with pure cultures of proteus vulgaris with neg- 

 ative or slight effects as regards the excretion of indican. 

 The lactic acid bacilli employed in similar experiments 

 in which cultures were injected directly into the small 

 intestine showed a tendency to cause a reduction in the 

 excretion of indican and of the ethereal sulphates. 1 



1 Herter, " On Certain Relations between Bacterial Activity in 

 the Intestine and the Indican of the Urine," Brit. Med. Jour., 

 II. p., 1847, 1897. 



