BACTERIAL ACTION IN THE INTESTINAL TRACT. 213 



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 indican 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 -f 2CO 2 , alcoholic fermentation. 



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



(3) C 6 H I2 6 = 2CH,.CH(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, aspartic 

 acid, and glutaminic acid. In the contents of the large intestine, 

 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. Indol is a derivative of the tryptophan complex, viz., of 

 skatol-amino-acetic acid (which see). Structurally it is closely 

 related to indigo, and according to Nencki, this transformation can 

 be effected through the action of ozone. It is represented by the 

 equation : 



/CO\ co 



4 " CH = 



Indol. Indigo. 



Conversely, indigo can be transformed into indol on reduction. 



From the albumins the substance can also be obtained on fusion 

 with potassium hydroxide. 



