ALBUMINS OR PROTEINS. 273 



acid. Embden 1 has shown that the alcapton acids are not produced when 

 the latter is administered. This investigation does not, however, pre- 

 clude the possibility that phenyl-acetic acid is one of the first degradation 

 products of phenyl-alanine, even from persons affected with alcaptonuria, 

 or that the disintegration of this amino acid does not proceed abnormally 

 from the very beginning. Efforts have been made to establish homogen- 

 tisic acid as a normal intermediate cleavage-product of phenyl-alanine 

 and tyrosine. 2 From this point of view, alcaptonuria would be looked 

 upon as a check on the complete combustion of the benzene nucleus. The 

 formation of homogentisic acid would then be looked upon as an oxidation 

 preceding the disruption of the benzene ring. The person afflicted with 

 alcaptonuria would not be capable of carrying this process to the end, as 

 a result of which, this anomalous metabolism produces a decomposition 

 product in the intermediate metamorphosis which would otherwise have 

 been lost to us. 



There is something very attractive in the suggestion that alcaptonuria 

 acts as a simple restraining influence in the normal disintegration of tyrosine 

 and phenyl-alanine. We must admit that this assumption has received 

 some support in the researches of Otto Neubauer and W. Falta. On the 

 other hand, we must remember that the manner of formation of the 

 alcaptonuric acids still remains a hypothesis, and that no absolute proof 

 of its truth has as yet been presented. 



The place of formation of the alcapton acids in the organism of a 

 patient afflicted with alcaptonuria was for a long time very much in 

 question. Wolkow and Baumann claimed that they were produced in 

 the upper part of the intestine, by the aid of micro-organisms. We 

 to-day believe that the alcapton acids are probably formed in the 

 tissues themselves. This conclusion follows from the fact that phenyl- 

 alanine, as far as known, is not set free by proteolytic ferments in the 

 alimentary tract. -The conditions are different with tyrosine. Large 

 quantities of this are set free in the intestine. This, under normal con- 

 ditions, is very largely assimilated, being even utilized by those affected 

 with alcaptonuria in the production of albumin, which is indicated by 

 the fact that the albuminous components of their blood show the same 

 amounts of tyrosine and phenyl-alanine, as do those of normal persons. 3 

 A small portion of the tyrosine is undoubtedly attacked by bacteria in the 

 intestine, in this way producing the various decomposition-products, until 

 phenol is reached. The intermediate products, p-hydroxyphenylpropionic 

 acid, and p-hydroxyphenylacetic acid, may also act as sources for the pro- 



1 H. Embden: Z. physiol. Chem. 18, 304 and 317 (1894). 



2 L. Gamier and S. Voisin: Arch, physiol. Ges. 6, 224 (1892). O. Neubauer and 

 W. Falta: Z. physiol. Chem. 42, 81 (1904). 



3 E. Abderhalden and W. Falta: Z. physiol. Chem. 39, 143 (1903). 



