30 INFECTIONS OF THE DIGESTIVE TRACT 



admitted that proof is wan ting that butyric acid formation 

 in the mouth is always due to anaerobes. The growth of 

 anaerobes in the mouth is favored by want of cleanliness 

 there, since the accumulation of food-masses encour- 

 ages anaerobic conditions beneath the surface. Probably 

 the intelligent and free use of the tooth-brush is a most 

 potent means of discouraging anaerobic growth in the 

 mouth. In removing decomposing food-masses one 

 not merely admits air to the anaerobes, but also removes 

 many aerobes which, through the symbiotic action 

 already mentioned, facilitate the multiplication of the 

 former. 



In the normal human stomach the conditions for the 

 development of anaerobic bacteria are usually poor, 

 partly on account of the presence of air, but mainly 

 owing to the action of the gastric juice. Nevertheless 

 the interior of a food bolus must often afford good 

 opportunities for the growth of anaerobes that happen 

 to be taken with the food. In a stomach which secretes 

 little or no hydrochloric acid, and which is sluggish in 

 emptying its contents, the chances for anaerobic develop- 

 ment are good, and hence we frequently find, under these 

 circumstances, that there are evidences of putrefactive 

 decomposition of food that has been unduly retained 

 in the stomach (e.g. production of sulphuretted hydro- 

 gen, mercaptan, butyric acid, etc.). Sometimes, too, 

 we have definite infections of the stomach wall with bac- 

 teria which are facultative anaerobes (e.g. streptococci), 

 and which are capable of inducing acute lesions of the 

 stomach. On the whole, however, I think one may say 



