CHAPTER X. 



BACTERIAL ACTION IN THE INTESTINAL TRACT. 



I HAVE pointed out in a preceding chapter that the gastric juice 

 possesses marked germicidal and antiseptic properties, so that a large 

 number of bacteria which are constantly swallowed with the saliva 

 and the food are subsequently destroyed in the stomach. A perfect 

 barrier to the invasion of micro-organisms, however, does not exist, 

 and after having passed the pylorus they are placed in surround- 

 ings which are in all respects most favorable to their develop- 

 ment. Here they take an active part in the decomposition of the 

 various food-stuffs which have escaped digestion in the stomach, and 

 further modify the digestive products which have already been 

 formed, as also those which result from the action of the various 

 intestinal ferments. The greater portion of the products of normal 

 digestion, however, escapes the specific activity of the bacteria, and 

 is absorbed in a form which can be utilized by the body for purposes 

 of nutrition. Formerly it was supposed that the biliary acids played 

 an important part in preventing undue activity on the part of the 

 bacteria, but this view has now been largely abandoned, and we are 

 totally ignorant as to the manner in which the body here protects 

 itself against excessive bacterial action. It has been argued that an 

 accumulation of the decomposition-products which result from the 

 action of bacteria upon the various food-stuffs in itself inhibits the 

 further activity of the organisms, but we can hardly regard such an 

 explanation as valid in view of the fact that in the intestines these 

 decomposition-products are to a large extent absorbed, and it seems 

 more probable that a vital activity of the epithelial cells is here 

 of prime importance. In the small intestine at least, where peri- 

 stalsis is extremely active, and where the intestinal contents are 

 churned in such a manner that the individual particles are almost 

 constantly in contact with the intestinal walls, we accordingly find 

 that bacterial action is not nearly so extensive as in the large intes- 

 tine, where the opposite conditions prevail. In the clinical labo- 

 ratory we find, as a matter of fact, that the degree of intestinal 

 putrefaction increases at once when the peristalsis of the small 

 intestine is impeded, and reaches its greatest height if the secretion 

 of hydrochloric acid becomes arrested at the same time. 



In former years a tendency existed among physiologists to regard 

 bacterial action in the intestine as serving a useful purpose, and it 

 was even supposed that, as in the case of plants, animal life could 

 not go on in the absence of micro-organisms from the alimentary 



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