INFECTIONS OF THE DIGESTIVE TRACT 153 



outside temporarily gain the numerical ascendency in 

 consequence of alterations in the nutrient media which 

 favor this race while repressing the ordinary dominant 

 one. In addition to a colon-bacillus diarrhoea associated 

 with colon bacilli of more than ordinary virulence, it is 

 probable that we must recognize a similar derangement 

 in which there is no increase of virulence on the part of 

 the bacilli, but simply an enormous physiological increase 

 which verges on the pathological. Almost any healthy 

 child who has eaten a largely excessive quantity of 

 ripe fruit, rich in sugar, will develop loose movements in 

 which colon bacilli are present in very large numbers. I 

 do not know whether these organisms are any more viru- 

 lent than the type dominant previous to the excessive 

 indulgence, but it seems extremely unlikely that they 

 suffer any appreciable change in the course of the short 

 interval of excessive fermentative activity. Acetic, 

 lactic, and other organic acids are formed in the course 

 of the fermentative process rendered possible by the 

 sugar-holding fruit, and it is to the irritant action of 

 these acids, and perhaps also to an excessive liberation 

 of gas, that the symptoms must be ascribed. Very 

 likely, too, in a case like this, bacilli of the group of B. 

 lactis aerogenes aid in the fermentation. In this instance 

 we are dealing clearly with a process on the borderland 

 between the physiological and the pathological. 



Of the influence exerted by colon bacilli in the course of 

 chronic processes within the digestive tract we have as 

 yet little knowledge, partly because etiological relations 

 are very difficult to establish in the case of obligate 



