BACTERIAL ACTION IN THE INTESTINAL TRACT. 197 



canal. This view has now been abandoned, however, especially 

 since Thierfelder and Nuttall were able to demonstrate that guinea- 

 pigs, after removal from the uterus of the mother by CaBsarean 

 section, can be maintained in perfect condition as to health and 

 body-weight when fed on sterile food and when furnished with 

 sterile air exclusively. On subsequent examination it was shown 

 that the intestinal contents of these animals were also sterile. We 

 may thus conclude that the presence of bacteria in the intestinal 

 contents is at best unnecessary, and it is doubtful, indeed, whether 

 they serve a useful purpose at any time. 



The action of bacteria upon the food-stuffs is in certain respects 

 quite analogous to that of the digestive ferments which are fur- 

 nished by the digestive glands of the animal body. The primary 

 digestion of the original material, however, does not cease with the 

 production of substances which the animal can subsequently utilize 

 for the purpose of replacing tissue, but is, on the whole, far more 

 extensive. Polysaccharides and disaccharides are thus not only 

 inverted to monosaccharides, but the latter are subsequently further 

 decomposed into material in which but little potential energy, if 

 any, remains stored. Albumins are similarly decomposed, with 

 the ultimate formation of substances which in part at least are dis- 

 tinctly toxic ; and the fats are divided into their components, which 

 are then further broken down, with the final formation of fatty 

 acids of the lowest order, etc. A great variety of decomposition- 

 products thus result from the normal food-stuffs, which are further 

 increased by those arising from material which the ferments of 

 the animal itself are incapable of digesting. To these are added 

 the decomposition-products of the various biliary constituents and 

 of the albuminous secretions which are poured into the intestinal 

 canal by the digestive glands themselves. 



As has been pointed out, the most intense degree of bacterial 

 action is observed in the large intestine, and it is interesting to 

 note that while albuminous putrefaction here prevails, the fermenta- 

 tive processes in the more restricted sense of the term, viz., the 

 decomposition of carbohydrates and fats, occur almost exclusively in 

 the small intestine. This difference may be dependent to a certain 

 degree upon the difference in the reaction of the intestinal contents 

 in the two sections of the gut that of the small intestine in its lower 

 portion at least being acid, while the reaction of the contents of the 

 large intestine is usually alkaline. But it is also possible that other 

 and still unknown factors determine this difference, and that the 

 varying reaction is primarily due to the decomposition-products 

 directly which result from the action of the bacteria. Among these 

 factors the relative amount of water may be of importance. 



Nencki, MacFadyen, and Sieber, who had occasion to study the 

 chemical composition of the intestinal contents in a patient in whom 

 an artificial anus had been established at the distal end of the ileum, 

 give the following account of their observations : The reaction, was 



