THE BACTERIA OF THE ALIMENTARY TRACT. 163 



are found in the mouth, as the inhabitants of this region are 

 simply carried through this tube by the swallowed saliva and 

 food. In the stomach the number of bacteria is greatly re- 

 duced, a large number of them, as will be shown later", being 

 destroyed by the gastric juice. Yet by no means all of them 

 are destroyed, the spore-bearing varieties being especially 

 successful in withstanding the action of the gastric juice. 

 Yet the other varieties such as the ordinary pus bacteria 

 can also traverse the stomach without losing their pathogenic 

 properties. It is certain that some at least of the majority 

 of the bacteria found in the mouth can pass the stomach and 

 be carried through the entire intestine uninjured, for MiLLER 1 

 was able to isolate from the stools 12 of 25 different varieties 

 which he had recognized in the mouth. 



Only few varieties of bacteria are found throughout the 

 small intestine. As the caecum is approached, however, 

 their number increases somewhat, to approach a maximum 

 in the ascending colon. From here to the rectum the sep- 

 arate varieties change but little. 



Though the last experiments have not yet been made in 

 this field it seems fairly certain that most of the strict anae- 

 robes are never found anywhere in the alimentary tract after 

 the stomach is passed. Of the varieties of bacteria which are 

 found we will not mention those which are recognized as the 

 cause of certain primary diseases, nor those which may be 

 found, but only those which, generally speaking, are almost 

 always present. Of these the following are the most im- 

 portant. 



As a constant inhabitant of the upper portions of the small 

 intestine of sucklings ESCHERICH has found the Bacterium 

 lactis aerogenes, which is able to exist here because of its power 

 of splitting up the milk-sugar of the food, from which it obtains 

 its necessary supply of oxygen. Corresponding with the 

 ever-diminishing amount of milk-sugar in the intestine from 



1 MILLER: Deutsche med, Wochenschr., 1885, p. 843, 



