THE AROMATIC CONSTITUENTS OF THE URINE. 255 



with an equal volume of ether. The nitrate is evaporated to dry- 

 ness, the residue acidified with hydrochloric acid, and extracted with 

 ether. The residue of the ethereal extract is then finally dissolved 

 in hot water. To remove the remaining hydrochloric acid, this 

 solution, after filtering and cooling, is again evaporated to dry ness 

 and redissolved in hot water. To demonstrate the presence of 

 skatol-carbonic acid, a portion of this final solution is then treated 

 with a few drops of pure nitric acid and a trace of potassium 

 nitrite. A red color thus develops, which may be extracted with 

 amyl alcohol or acetic ether. This solution shows a band of absorp- 

 tion in the green portion of the spectrum. On adding a solution of 

 sodium hydrate to the ethereal solution the red color disappears, but 

 reappears on the subsequent addition of hydrochloric acid. 



In addition to the aromatic bodies which have thus far been con- 

 sidered, traces of the aromatic oxy-acids may also appear in the 

 urine in combination with sulphuric acid, but the amount is exceed- 

 ingly small, and may well be ignored. 



The Conjugate Glucuronates. 



Glucuronic acid as such does not occur in the urine. The sub- 

 stance can combine with various aromatic bodies, however, and may 

 in this manner escape further oxidation in the body. Normally, it 

 is found only in traces, in combination with indoxyl, skatoxyl, 

 phenol, and paracresol, while the greater portion of these substances 

 is eliminated in the form of conjugate sulphates, as has been pointed 

 out. Larger quantities are found in the urine after the administra- 

 tion of chloral, camphor, naphtol, oil of turpentine, menthol, toluol, 

 euxanthin, morphin, etc. With these it forms compounds which are 

 closely related to the glucosides. According to the character of the 

 aromatic component, the resulting glucuronates have been termed 

 campho-glucuronic acid, menthol-glucuronic acid, urochloralic acid, 

 phenyl-indoxyl-skatoxyl-glucuromc acid, etc. 



Of the origin of the glucuronic acid, and its fate under normal 

 conditions, we know little. That it is formed in the tissues of the 

 body is apparent from the fact that even in a starving animal the 

 administration of camphor, chloral, etc., leads to elimination of these 

 substances in combination with the acid in question. As glucuronic 

 acid is a derivative of glucose, we may thus imagine that during 

 starvation it is derived from glycogen, or even from the albumins, 

 through a splitting off of the carbohydrate group. It has been 

 demonstrated, as a matter of fact, that the formation of glycogen in 

 the liver can be artificially increased by introducing glucuronic acid 

 with the food. The chemical relation of glucuronic acid to glucose 

 has already been considered. On oxidation glucose thus first yields 

 the monobasic glucuronic acid, and then the dibasic saccharinic acid. 

 The latter in turn may be transformed into saccharo-lactonic acid, 

 which on reduction yields glucuronic acid, so that this stands mid- 



