

INDICAN. 487 



In the presence of melanotic neoplasms, black urine has from time to time 

 been observed, due to melanin or a pigment containing iron. 



A brown pigment containing iron is carried down by the uric acid precipitated 

 on addition of hydrochloric acid. By repeated addition of sodium urate to urine 

 and precipitation of the uric acid by hydrochloric acid, this pigment can be 

 obtained in considerable amount. 



SUBSTANCES FORMING INDIGO, PHENOL, KRESOL, PYROCATE- 

 CHIN, AND SKATOL. OTHER SUBSTANCES. 



Indican, or the indigo-forming substance, is derived from indol, 

 C 8 H 7 N, the mother-substance of indigo, which is formed in the intestine 

 as a result of the pancreatic digestion of proteids, and as a putrefactive 

 product. The indol, conjugated with the sulphuric-acid residue, SO 3 H, 

 and combined with potassium, represents the indican, or indigogen of 

 the urine (C 8 H 6 NSO 4 K, potassium indoxylsulphate). It forms white 

 glistening tables and plates, readily soluble in water, slightly in alcohol. 

 By oxidation it forms indigo-blue : 



2 indican -f- O 2 = C 16 H 10 N 2 O 2 (indigo-blue) -j- sHKSO 4 (acid potassium sulphate). 



Jaffe found between 4.5 and 19.5 mg. of indigo in 1500 cu. cm. of normal 

 human urine. Indigo is more abundant in the urine of inhabitants of the tropics, 

 less abundant on a milk-diet, and it is wanting in the new-born. The urine of 

 horses contains 23 times as much as human urine. Subcutaneous injections of 

 indol increase the amount of indican in the urine. E. Ludwig obtained indican 

 by heating hematin or bilirubin with potassium hydrate and powdered tin. It 

 has been found also in the sweat. 



Demonstration. One-half of a test-tubeful of urine is mixed with an equal 

 amount of hydrochloric acid, and 2 drops of a freshly prepared solution of chlorin- 

 ated lime are added. The mixture becomes at first clear, then grayish blue. 

 Now a few drops of chloroform are added, and the mixture is persistently agitated, 

 the pigment being dissolved by the chloroform. If the mixture is permitted 

 to stand, the blue chloroform-layer is deposited at the bottom. For quantitative 

 estimation, the indican is transformed into indigo and further into sulphoindigotic 

 acid, and this is titrated with a solution of potassium permanganate. Certain 

 bacteria may produce indigo-blue in the evacuated urine, but also in the urinary 

 passages; therefore, a lustrous bluish-red coating of microscopic rhombic crys- 

 tals of indigo-blue upon the surface of putrid urine, or a precipitate thereof, is 

 occasionally observed (Heller's uroglaucin) . 



Pathological. Indican is increased in the urine when the formation of indol 

 is increased in the intestines in consequence of active putrefactive fermentation; 

 as, for instance, in cases of typhoid fever, lead-colic, trichinosis, gastro-intestinal 

 catarrh, hemorrhage from the stomach or bowel, diseases of the small intestine, 

 cholera nostras, carcinoma of the liver and the stomach, strangulated hernia, 

 peritonitis. As indican is developed as a result of the decomposition of pus, an 

 increased amount in the urine may indicate the presence of suppuration, when 

 the intestinal conditions are normal. 



Urine boiled with hydrochloric acid yields to the ethereal extract, together with 

 indigo-blue, a garnet-red pigment, crystallizing in rhombic plates, namely indigo- 

 red, urorubin, urorosein, which is developed by oxidation from an unknown 

 chromogen. Its amount depends upon the same conditions as does that of 

 indican. The urine thus extracted yields a brownish-black pigment to amylic 

 alcohol, namely, uromelanin. All urinary pigments that are produced through the 

 activity of acids are contaminated by dark-colored, nitrogenous humin-sub- 

 stances, which are formed, in part, from the carbohydrates of the urine. 



Reaction for* Indigo-red. One- quarter of a test-tubeful of urine is boiled con- 

 tinuously, with addition of nitric acid, drop by drop, until a red color is produced; 

 it is then cooled and rendered alkaline with ammonia. If now it be gently 

 agitated with 2 cu. cm. of ether, indigo-red dissolved in the ether passes over. 

 The red reaction takes place in the presence of insufficiency of the intestine and 

 its glands, in conjunction with severe diarrhea and most profound nutritive 

 disorders. 



