THE AROMATIC CONSTITUENTS OF THE URINE. 251 



is increased, or in cases in which putrefactive changes are taking 

 place in the body proper, as in empyema, providing that active 

 resorption can occur. 



In herbivorous animals larger amounts are found than in the 

 carnivora. Artificially an increased elimination can be effected by 

 feeding animals with ortho-nitro-phenyl-propiolic acid, which is 

 reduced in the body to indoxyl, according to the equation : 



C=COOH C.OH=CH 



+3H ' 



Ortho-nitro-phenyl- Indoxyl. 



propiolic acid. 



Indican crystallizes in colorless platelets, which are readily soluble 

 in water and hot alcohol, while in cold alcohol they dissolve with 

 great difficulty. On decomposition with hydrochloric acid the 

 indoxyl is obtained in the form of oily droplets of an exceedingly 

 offensive, feculent odor. On oxidation this is then transformed into 

 indigo-blue, as is shown in the equation : 



X C.OH = CH /CO x /CO v 



2C 6 H/ +20 = C 6 H/ >C=C< >C 6 H 4 -f2H 2 



\NH \NH/ \NH/ 



Indoxyl. Indigo-blue. 



On heating an aqueous solution of indoxyl to a temperature of 

 130 C. indoxyl-red also results. This is a brown amorphous sub- 

 stance, which is insoluble in water, but dissolves with ease in 

 alcohol, ether, and chloroform, with a beautiful red color. When 

 Jaffe's test for indican is applied to the urine, or when this is boiled 

 and treated drop by drop with concentrated nitric acid (Rosenbach's 

 reaction), a mixture of a blue and a red pigment is not infrequently 

 obtained, and it is quite likely that the latter is in part at least refer- 

 able to the formation of the indoxyl-red. According to some observ- 

 ers, the chromogen of this substance is identical with the so-called 

 urohsematin, and the pigment is probably the same as the red pig- 

 ment of Scherer, the urrhodin of Heller, the urorubin of Plosz, the 

 indirubin of Schunk, the indigo-purpurin of Bayer, the pigment 

 of Giacosa and others. 



The blue pigment which is found together with the red pigment 

 when urine is treated with a strong mineral acid and an oxidizing 

 agent is, as has been indicated, indigo-blue, and is identical with 

 urocyanin, cyanurin, Harnblau, uroglaucin, etc., of former observers. 

 As a general rule, its amount is far greater than that of the red pig- 

 ment, and is at times the only one that is obtained. In other cases, 

 however, the red seems to prevail, and in still others both are appar- 

 ently present in about equal proportion. The cause of these varia- 

 tions is as yet not understood, but probably rests upon variations in 

 bacterial action in the intestinal tract. As a general rule, indeed, 

 notable quantities of the red pigment are observed only under pa.tho- 

 logical conditions. 



