198 BACTERIAL ACTION IN THE INTESTINAL TRACT. 



quite constantly acid, owing to the presence of organic acids, and 

 notably of acetic acid. Other acids that were present were lactic 

 acid, paralactic acid, various volatile fatty acids, succinic acid, and 

 the biliary acids. The odor but rarely suggested the existence of 

 putrefactive changes. Indol, skatol, and phenol could not be 

 demonstrated as such, although the urine contained inclican on 

 several occasions. Leucin and tyrosin were not found. Alcohol 

 could always be demonstrated. Of gases, carbon dioxide was ob- 

 served, as also faint traces of hydrogen sulphide, while methyl- 

 mercaptan was absent. 



Carbohydrate fermentation thus manifestly stands in the fore- 

 ground, and is exemplified in various types by the equations : 



(1) C 6 H 12 O 6 = 2C 2 H 5 .OH + 2CO 2 , alcoholic fermentation. 



(2) C 2 H 5 .OH -f 2O = CH 3 .COOH + H 2 O, acetic acid fermentation. 



(3) C 6 H |2 O 6 = 2CH 3 .CH 2 (OH)COOH, lactic acid fermentation. 



(4) 2C 3 H 6 O 3 = C 3 H 7 .COOH + 2CO 2 + 4H, butyric acid fermentation. 



The products of albuminous putrefaction, on the other hand, are 

 almost exclusively formed in the large intestine. Primarily they 

 are in part at least the same as those which result from the action 

 of trypsin on albumins, and in experiments in vitro we thus find 

 albumoses, peptone-like bodies, tryptophan, leucin, tyrosin, aspara- 

 ginic acid, and glutaminic acid. In the contents of the large intes- 

 tine, however, these substances are found only in traces, so that we 

 are forced to the conclusion that they are either absorbed as soon as 

 formed or that they are further decomposed. Both, no doubt, 

 occurs, and related bodies are, as a matter of fact, encountered in 

 the feces. As a result of bacterial activity still other substances 

 are formed, however, which are apparently not derived from the 

 final products of digestion, but which are formed from the more or 

 less intact albuminous molecule directly. 



The more important decomposition-products which result from 

 the action of bacteria upon the products of albuminous digestion are 

 here considered. 



Indol. We have seen that on decomposition of the albumins 

 with trypsin, as also with boiling mineral acids, the aromatic 

 groups of the albuminous molecule are split off in the form of 

 tyrosin i. e., a body belonging to the para-series. Indol, on the 

 other hand, belongs to the ortho-series, and cannot be obtained in 

 this manner. It is a specific product of albuminous putrefaction, 

 and it would, of course, be interesting to ascertain why the aromatic 

 groups in the one case are set free exclusively in the form of 

 tyrosin, while in the other both result side by side. At present we 

 are unable to offer an adequate explanation of this phenomenon, but 

 it is possible, as Neumeister suggests, that certain bacteria produce 

 i i idol synthetically from simpler aromatic groups. We find, as a 



