250 BACTEEIOLOGY 



function, and he believes that the duty has fallen to 

 them of carrying on a ' digestion bacterienne ' by their vital 

 action. 



Under normal conditions the microbes lie on the inner 

 surface of the intestine, but in pathological processes the 

 parasites penetrate between the epithelia of the villi, thence 

 into the interior of the villi, and eventually through the 

 intestinal parietes to the peritoneum. 



Articles of food which contain bacteria increase the 

 number of colonies obtained from the contents of the gut 

 to a very considerable extent, while the ingestion of sterile 

 food-stuffs or of red wine causes, according to Arnold, the 

 appearance of a striking diminution in the number of 

 germs. 



According to Duclaux, only those bacteria can develop 

 luxuriantly in the intestine which have no stringent need of 

 oxygen ; but Abelous sets up the hypothesis that although 

 the oxygen necessary for the existence of aerobes occurring 

 in this situation can, in point of fact, reach the intes- 

 tine with the saliva, the intestinal micro-organisms have 

 the power of accommodating themselves to a deficiency 

 of it. 



Most of the bacteria living upon the mucous membrane 

 are saprophytes ; the pathogenic varieties are present only 

 in small numbers, and often perish by being overgrown by 

 the former, while many pass away in the faeces. According 

 to Nothnagel, a very large number of yeast- cells are found 

 in the contents of the gut, so much so that Brefeld seeks the 

 normal habitat of yeast in the large intestine. 



Micrococcus aerogenes. — Miller found in the digestive 

 tract fairly large non-motile cocci of oval outline, which are 

 distinguished for their marked power of resisting acids, 

 and hence do not lose their vitality in acid digestive juices. 

 Gelatine is slightly liquefied. The colonies on plate-cultures 



