146 OXYPROTEIC ACIDS 



which may be found in the urine in the form of imidazol- 



CH.NEL 



II >CH 



C N / 



aminopropionic acid (histidin), CH 2 , and of imidazol- 



CH.NH 2 



COOH 

 CH-NH, 

 R >CH 



C - N^ 



aminoacetic acid, I . It is said that the puzzling 



CH.NH 2 



COOH. 



"urocaninic acid" of dogs' urine is also an imidazol deriva- 



CH-NH. 



II >CH 



C - N^ 



CH , obtainable from histidin by ammonia cal 



CH 



COOH 

 cleavage. 73 



Other High-molecular Residual Substances. In addi- 

 tion to the oxyproteic acids there are other high-molecular 

 metabolic residual substances of various kinds in the urine, 

 about which we know practically nothing. E. Abder- 

 halden and F. Pregl, 74 after freeing an alcoholic extract 

 of urine of urea and other easily diffusible materials by 

 dialysis, obtained a mixture of substances which contained 

 no free aminoacids but after acid hydrolysis yielded a num- 

 ber of typical protein cleavage products. It is impossible 

 at the present to decide the extent to which these substances 

 are related with the oxyproteic acids (which unquestionably 

 hydrolytically yield aminoacids 75 ) or with typical poly- 

 peptids. It seems that they may be met in small amount in 

 normal urine and somewhat more in disease, as in cancer 



"A. Hunter (Cornell Univ.) , Jour, of Biol. Chem., 11, 537, 1912. 

 74 E. Abderhalden and F. Pregl, Zeitschr. f. physiol. Chem., 46, 19, 1905. 

 78 W. Ginsburg, Hofmeister's Beitr., 10, 441, 1907; J. Browinski and S. 

 Dombrowski (Lemberg), Zeitschr. f. physiol. Chem., 77, 92, 1912. 



