128 INFECTIONS OF THE DIGESTIVE TRACT 



to the transference to the tube of some nutritive sub- 

 stance contained in the intestine. 



By far the greatest value of the gas production in the 

 fermentation tubes is in those cases in which the gas 

 production is much below normal. This diminution in 

 gas formation is not a variable occurrence, but in the 

 case of the same individual is persistent so long as the 

 conditions of diet and habits of life remain the same. 

 It is, in fact, an individual peculiarity. As already 

 stated, it appears to depend on the elimination of typical 

 colon bacilli. This view has been supported repeatedly 

 by the results of plating upon litmus gelatin. The dis- 

 appearance of the colon bacilli is occasionally met with 

 in persons apparently in good health, but I believe this 

 to be a very exceptional occurrence. Ordinarily the 

 inability to produce gas in normal abundance is a sign 

 of a temporary or persistent alteration in the character 

 of the intestinal flora. There are instances, indeed, in 

 which we have been unable to obtain any gas whatever 

 in some or all of the sugar-bouillon tubes. These have 

 been usually instances of an extremely marked form of 

 saccharo-butyric putrefaction and have not been very 

 uncommon among cases of pernicious anaemia associated 

 with an infection with B. aerogenes capsulatus and the 

 disappearance of the colon bacilli. This disappearance 

 has been noted also in some cases of mucous colitis 

 in which a foreign race of colon bacilli (or organisms 

 intermediate between colon bacilli and typhoid or para- 

 typhoid bacilli) have been found to be the dominant 

 representatives of the colon bacillus group. 



