ALBUMINS OR PROTEINS. 255 



They have both been obtained from urine, partly as conjugated sulphuric 

 acids, but mainly in the form of salts. 



It is questionable whether these two compounds are always and invari- 

 ably produced by intestinal putrefaction. It is possible, in fact probable, 

 that these two hydroxy-acids are produced by the decomposition of tyro- 

 sine in the tissues. Confirming this is the fact noted by H. Thierfelder 

 and Nuttal, 1 that these two acids were observed in the urine of guinea pigs 

 which had been kept sterile, 2 i.e. they had grown up with their intestinal 

 tracts free from bacteria, consequently there could not be any putre- 

 faction. It is important that the urine of these animals did not contain 

 any typical putrefactive products of proteins; i.e. the phenols. 



Para-hydroxymandelic acid, 



C 6 H 4 . OH . CH . (OH) . COOH, 



has also been found in the urine, although only under specific conditions. 

 Schultzen and Ries 3 found it in acute cases of atrophy of the liver. 



Blendermann, 4 after feeding tyrosine to a dog, found a dihydroxyphenyl- 

 propionic acid: 



HO . C 6 H 4 . C 2 H 3 (OH) . COOH, 

 in the urine. 



If we review the investigations just mentioned, we shall see that the same 

 groups of decomposition products are obtained by intestinal putrefaction 

 of tyrosine as are obtained by the same process outside the animal 

 organism. 5 From tyrosine, 



/OH 



p-hydroxyphenylaminopropionic acid: C6H 4 



X CH 2 .CH(NH 2 ) COOH 

 we obtain the following decomposition products: 



p-hydroxyphenylpropionic acid: CeH 4 



X CH 2 .CH 2 .COOH 

 ,OK 



p-hydroxyphenylacetic acid: CeH 4 



X CH 2 .COOH 

 ,0V 



p-cresol: CeH 4 



X CH 3 

 phenol: C 6 H 5 . OH 



1 H. Thierfelder and Nuttal: ibid. 21, 109 (1896); 22, 62 (1897). 



2 Cf. Lecture IV, p. 64. 



3 Schultzen and Ries: Ueber akute Phosphorvergiftung u. Leberatrophie, Berlin, 1869. 



4 H. Blendermann: loc. cit. 

 6 Cf. Lecture VIII, p. 171. 



