98 UREA. HIPPURIC ACID. AMINOACIDS 



literature of the subject, may to-day be consigned finally to 

 well deserved rest. There was a time when it was entirely 

 proper to think it possible that urea may be formed in the 

 body precisely as in Wohler's synthesis by transformation 

 from ammonium cyanate; but after vainly searching for 

 hydrocyanic acid for a number of decades in the intermediate 

 metabolism the theory may be finally dropped, in the 

 author's opinion, from current consideration. If we are to 

 drag along the whole dead weight of wornout mistakes of 

 former generations on our backs, how can we be expected to 

 acquire the strength and vigor required for the grinding 

 effort to reach the higher levels of the future! 



Uraminoacids. The formation of certain conjugate 

 products, the ur amino acids , suggesting the possible avail- 

 ability of free CONH 2 complexes, may be regarded as favor- 

 ing Hofmeister's theory. Thus, as Salkowski discovered, 

 aminobenzoic acid and sulphanilic acid introduced into the 

 system, as, too, taurin, can attach CONH 2 groups to them- 

 selves ; and even ingested tyrosin may be observed linked 

 with such a complex (cf. Vol. I of this series, p. 47, Chemistry 

 of the Tissues) : 



m = AMINOBENZOIC ACID SULPHANILIC ACID 



/NH 2 XNH.CO.NHj /NH 2 /NH.Co.NH 2 



CH 4 >C&4 ; C 6 H 4 >C,R t 



\COOH \COOH \HSO 3 \HSO 8 



TAURIN 



CH 2 .NH 2 CH 2 .NH.CO.NH 2 



CH 2 HSO 3 " CH 2 HSO, 



TYROSIN 



OH.Cja, CH 2 OH CH 4 -CH 2 



CH.NH 2 > CH.NH.CO.NH 2 



COOH COOH. 



But it has been proved that in alkaline reaction aminoacids 

 with urea are very readily transformed into uraminoacids. 1 



1 F. Lippich, Ber. d. deutsch. chem. Ges., 39, 2953, 1906; 41, 2053, 2074, 

 1908. 



