90 THE NITROGENOUS DERIVATIVES OF THE ALBUMINS. 



In the animal body paracresol and phenol, which are formed from 

 tyrosin during the process of intestinal putrefaction, then combine 

 with sulphuric acid, and are eliminated through the urine in the 

 form of their potassium salts : 



/OH /OH /O.HSO, 



C 6 H 4 < + SO/ = C 6 H 4 < + H 2 0. 



\CH \OH 



/OH 

 C 6 H 5 .OH + SO 2 / = C 6 H 5 .O.HSO 3 + H 2 O. 



During the process of albuminous putrefaction other aromatic 

 compounds besides tyrosin and its derivatives also result, but these, 

 in contradistinction to tyrosin, belong to the ortho-group. They 

 comprise indol, skatol, and skatol-carbonic acid. According to some 

 observers, these substances are derived from a special aromatic radicle, 

 which is contained in the albuminous molecule, and which differs 

 from the tyrosin radicle, while others believe that they result syn- 

 thetically through the influence of the living bacteria from certain 

 aromatic groups, which on hydrolytic decomposition with acids give 

 rise to tyrosin. 



Indol, skatol, and skatol-carbonic acid are closely related to each 

 other and to indigo. Skatol thus results from indol through a sub- 

 stitution of the methyl-group for a hydrogen atom of one of the CH 

 groups, as shown by the formula : 



<' CT '' 



Indol. Skatol. 



Skatol-carbonic acid then results from skatol through a union with 

 carbon dioxide : 



^C.COOH 



Skatol-carbonic acid. 



In their passage through the animal body indol and skatol are 

 oxidized to indoxyl and skatoxyl, and are eliminated in the urine to 

 a great extent, in combination with sulphuric acid, as potassium 

 indoxyl sulphate (animal indican) and potassium skatoxyl sulphate, 

 while the skatol-carbonic acid is excreted as such. These changes 

 can be expressed by the equations : 



CH 



Indol. Indoxyl. 



/C(OH) v \ /C(O.SO 3 H), 



(2) C 6 H/ ^>CH + H 2 SO 4 *= r-TT./ 



Indoxyl. Indican. 



