202 BACTERIAL ACTION IX THE INTESTINAL TRACT. 



more important products of albuminous putrefaction are described in 

 the chapter on the Feces. 



BACTERIAL DECOMPOSITION OF THE FATS. 



As in the case of the carbohydrates and albumins, a comparatively 

 small portion of the fats only undergoes bacterial decomposition, and 

 it appears that this principally occurs in the lower portion of the 

 .-mall intestine. As in the case of the steapsin of the pancreatic 

 juice, the neutral fats are thus first decomposed into glycerin and 

 the corresponding fatty acids, but the process extends further, 

 and as a result a gradual reduction of the higher acids to the lowest 

 forms takes place. To a certain extent these are then absorbed and 

 further decomposed in the body, but a not inconsiderable portion is 

 directly eliminated in the feces, and we accordingly find here repre- 

 sentatives of the group, from palmitic, stearic, and oleic acids down 

 to butyric acid and acetic acid. The glycerin is absorbed, and is to 

 a certain extent no doubt utilized by the epithelial cells in the syn- 

 thesis of fats. 



The lecithins are decomposed in the same manner as under the 

 influence of steapsin, with the formation of glycerin-phosphoric acid, 

 fatty acids, and cholin. Whether or not the latter may then be 

 transformed into neurin is not known, but under normal condi- 

 tions this probably does not occur. The glycerin-phosphoric acid 

 is subsequently no doubt absorbed together with some of the fatty 

 acids, and appears in the urine as such. The cholin, on the other 

 hand, is further decomposed, with the formation of ammonia, carbon 

 dioxide, and methane. 



BACTERIAL DECOMPOSITION OF THE BILIARY CON- 

 STITUENTS. 



In former years it was generally supposed that the biliary acids 

 after their elimination into the intestinal canal were there absorbed 

 to a large extent and returned to the liver, while a smaller portion 

 was decomposed and eliminated in the feces. Some observers even 

 now maintain the occurrence of such a circulation of the bile-acids, 

 but there is a strong tendency among physiologists at present to 

 deny its existence. As a matter of fact, bile-acids are not found in 

 the blood or in the urine under normal conditions. 



In the human being, moreover, dyslysins are found only in the 

 feces, while the amido-radicles have apparently been decomposed. 

 In other animals glycocholic acid has been found, but taurocholic 

 acid apparently always succumbs to the action of the bacteria. 

 Of the fate of the amido-radicles we know little, but it is possible 

 that both are in part further decomposed and in part absorbed. 

 Taurin may then appear in the urine either as such or as tauro- 

 carbaminic acid ; but it may, on the other hand, again combine 

 with cholalic acid and reappear in the bile. The glycocoll similarly 

 may in part be transformed into urea; or it may combine with the 



