20 INFECTIONS OF THE DIGESTIVE TRACT 



really only inhibitory and not bactericidal, leaving the 

 bacteria still capable of growth when brought into better 

 nutrient media, so many of the bacteria in the fseces 

 have been killed. The proof remains to be furnished 

 that the death of these bacteria in the lower part of the 

 intestinal tract and the inhibition at higher levels are 

 due to the same cause. 



It is only fair to say that Conradi and Kurpjuweit 

 have not succeeded in establishing their contention that 

 the inhibitory action of colon bacilli is due to specific 

 toxines which they form. The inhibitory action de- 

 scribed by them is certainly due in part to the exhaustion 

 of the media by the freely growing colon bacilli and in 

 part to the production of acid, indol, phenol, or other pu- 

 trefactive or fermentative substances. It would be going 

 too far, however, to deny that substances at present 

 unknown to us may possibly have a part in bringing 

 about the phenomena of inhibition. 



It is clear that the colon bacilli can act protectively 

 to the digestive tract only when they are able to grow 

 freely. If the conditions are such in the tract that they 

 cannot multiply abundantly, they can neither exhaust 

 the nutritive materials on which other races grow nor 

 make products endowed with inhibitory powers. There 

 are many examples of disease in which the colon bacilli 

 disappear not merely from the faeces, but from the 

 diarrhceal stools. Other races take their place. This 

 condition is quite unintelligible unless we assume that 

 the colon bacilli no longer find a suitable nutrient medium 

 in the mixture of digestive juices and food. Without 



