316 PHYSIOLOGICAL CHEMISTRY. 



reaction carbamic acid is the immediate forerunner of the urea. 

 It may be formed from some amino acids by oxidation proc- 

 esses and in turn passes to urea by this reaction, 



NH 2 O CO NH 2 + H 2 = NH 2 CONH 2 + H 2 O, 



in which a reduction process is finally in play. The carbamic 

 acid may be produced by oxidation directly of the ammonium 



salt, 



NH 4 O CO NH 2 + O = NH 2 O CONH 2 + H 2 O, 



so that both oxidations and reductions may be concerned. 

 However, we are certain of the final result only, and are not 

 able to give the steps definitely. 



The Formation of Ethereal Sulphates. Another reac- 

 tion of far-reaching importance in the body is the production 

 of organic sulphates. The oxidation of the sulphur of pro- 

 teins leads finally, mainly, to the formation of sulphuric acid 

 which is eliminated in the urine in the form of the ordinary 

 mineral sulphates and the ethereal sulphates. The mineral 

 sulphates are readily formed directly by combinations in the 

 blood, but for the union of the organic groups with sulphuric 

 acid some active agent is required. The addition seems to 

 take place in the liver where it is probable that the oxidation 

 of the sulphur-containing complex, furnished by protein dis- 

 integration, also occurs. This complex seems to be cystein, 

 which is easily oxidized to cystin, and experiments with ani- 

 mals have shown that cystein administered increases largely 

 the sulphates of the urine. Several attempts have been made 

 to determine the seat of the reaction by irrigation tests, and 

 comparatively recently it has been shown that blood containing 

 phenol and cystin and led through the liver, freshly dissected, 

 discloses a very considerable oxidation of the sulphur com- 

 pound with production of aromatic sulphate. It appears that 

 other organs are not much concerned, if at all, in the reaction. 



The aromatic radicles which join with sulphuric acid in this 

 way are mainly products of intestinal putrefactive changes, 

 and by absorption finally reach the liver. In addition to sul- 



