THE URINE. 369 



paraoxyphenyi-propionic acid, C 6 H 4 (OH).C 2 H 4 .COOH, are formed 

 from tyrosin as intermediate steps, and these pass unchanged into 

 the urine. They were first detected by BAUMANN. The quantity 

 of these acids is usually very small. They are increased by the 

 same circumstances as phenol, especially in acute phosphorus-poi- 

 soning, in which the increase is considerable. In acute atrophy of 

 the liver another oxyacid, oxytnandel-acid, has been found in the 

 urine (SCHULTZEN and RIESS). 



The above two acids are soluble in ether. On warming with MILLON'S 

 reagent they give a beautiful red color. To detect the presence of these oxy- 

 acids proceed in the following way (BAUMANN) : Warm the urine for a while 

 on the water-bath with hydrochloric acid, in order to drive off the volatile 

 phenols. After cooling shake three times with ether, and then shake the 

 ethereal extracts with dilute soda solution, which dissolves the oxyacids, while 

 the residue of the phenols soluble in ether remains. The alkaline solution of 

 the oxyacids is now faintly acidified with sulphuric acid, shaken again with 

 ether, the ether removed and allow to evaporate, the residue dissolved in a 

 little water, and the solution tested with MILLON'S reagent. The two oxyacids 

 are best differentiated by their different melting-points. The reader is referred 

 to other works for the method of isolating and separating these two oxyacids. 



Uroleucic Acid, C 9 H,oO 6 . This acid in a pure state was first prepared by 

 MARSHALL from urine, but named and specially studied by KIRK. In an im- 

 pure state it forms the reducible substance ALCAPTON discovered by BOEDE- 

 KER. This acid is especially found in children's urine. Such urine reduces 

 FEHLING'S reagent, but not an alkaline bismuth or picric-acid solution. It is 

 fermentable, optically inactive, and is colored deep brown in the air, espe- 

 cially in an alkaline solution. In these respects it differs from a urine con- 

 taining sugar. 



Urinary Coloring Matters and Chromogens. The yellow color of 

 normal urine depends apparently upon several coloring matters 

 (VIERORDT) which have not been isolated and studied. Besides 

 these bodies, UROBILIN sometimes occurs in fresh normal urine, but 

 by no means always. Instead of urobilin, normal urine often con- 

 tains a mother-substance of the same, a chromogen or UROBILINOGEN, 

 from which the urobilin is gradually formed by oxidation on allow- 

 ing the urine to stand exposed to the air (JAFFE, STOKVIS, DISQUE, 

 and others). Besides this chromogen, urine contains various other 

 bodies from which coloring matters may be produced by the action 

 of chemical agents. Humous substances (perhaps in part from the 

 carbohydrates of the urine) may be formed by the action of acids 

 (v. UDRANSZKY and HOPPE-SEYLER) without regard to the fact 

 that such substances may sometimes originate from the reagents 

 used, as from impure amyl-alcohol (v. UDRANSZKY and HOPPE- 



