ALBUMINS OR PROTEINS. 257 



In this connection we would add, that two other acids, closely related 

 to tyrosine and phenylalanine, namely, homogentisic acid and uroleucic 

 acid, have also been found in rare cases in urine. The former is a dihy- 



droxyphenylacetic acid: 



X OH 



C 6 H 3 OH 



X CH 2 .COOH 



the latter, a dihydroxyphenyllactic acid. They are both found during an 

 abnormal metabolism in the so-called " alcaptonuria." 



Let us turn from our discussion of the tyrosine and phenylalanine de- 

 composition products to the sulphuric acid esters. We have already con- 

 sidered the occurrence of indoxyl- and skatoxyl-sulphuric acids in urine. 

 Intestinal putrefaction of albumin produces indole: 



CH 



// \ 

 HC C CH 



I II II 



HC C CH 



^ / \ / 

 CH NH 



and skatole (methyl-indole) : 



CH 



HC C C . CH 3 



I II II 



HC C CH 3 



^ / \ / 

 CH NH 



They are oxidized in the tissues to indoxyl: 



CH 

 // \ 



HC C C(OH) 



I II II 



HC C CH 



^ / \ / 



CH NH 

 and skatoxyl: 



and then combined with sulphuric or glucuronic acids. 



We will at once state that skatoxylsulphuric acid has not been detected 



