INFECTIONS OF THE DIGESTIVE TRACT 215 



digestive tract may be dismissed with few words. The 

 carbon dioxide which results from the breakdown of 

 sugars is of interest mainly as a cause of gastric flatu- 

 lence or small-intestinal flatulence. The alcohol formed 

 is probably in too small amount to be toxically significant 

 even when fermentation of sugars is greatly excessive. 

 Of the acids formed we have to think of lactic, acetic, 

 propionic, and butyric, but mainly of lactic and acetic. 

 The higher volatile fatty acids come especially from 

 spore-bearing anaerobes (although other types of bacteria 

 may produce them) and therefore interest us also as 

 putrefactive products. All these acids, however, are 

 irritants by virtue of their acid properties. If present 

 in considerable concentration in a healthy digestive 

 tract or in more moderate concentration in the tract of a 

 person with an irritable stomach or small intestine, they 

 may be efficient factors in exciting vomiting or diarrhoea. 

 Nervous disturbances resulting in delayed absorption 

 may be responsible for the accumulation of considerable 

 acid fluid in the stomach or small intestine. There is 

 also a quite different aspect to the excessive production 

 of acid ; namely, the withdrawal of excessive amounts of 

 alkali from the organism. All the acids mentioned are 

 readily burned in the body, but if their absorption occurs 

 with uncommon rapidity, they may be excreted unburned 

 and combined with alkali. This robbing of the organism 

 -of alkali by acid is under some conditions a grave matter, 

 leading to a definite form of intoxication, but probably 

 the acids of fermentative origin are always associated 

 with those of putrefactive origin in bringing about this 



