252 THE UEINE. 



Tests for Indican. All the tests employed for the purpose of 

 demonstrating the presence of indican in the urine are essentially 

 based upon the decomposition of the substance, with the liberation 

 of indoxyl and its oxidation to indigo-blue. 



JAFFE'S TEST, AS MODIFIED BY STOKVIS. A few cubic cen- 

 timeters of urine are treated with an equal volume of concentrated 

 hydrochloric acid, and two or three drops of a strong solution of 

 sodium hypochlorite. The indigo-blue which thus results is then 

 extracted by shaking with a little chloroform. If red pigment has 

 been formed at the same time, the color varies from a violet to a 

 purplish red. 



If it is desired to separate the two pigments, the chloroform extract 

 is evaporated to dry ness and the residue washed with a mixture of 

 equal parts of 96 per cent, alcohol, ether, and water. This dissolves 

 the red pigment and leaves the indigo-blue behind. Care must be 

 had, however, not to add too much of the hypochlorite solution, as 

 otherwise the indigo-blue is oxidized to indigo-white, and no color 

 at all is obtained. Should this happen after the addition of only 

 one or two drops, the following test had better be employed, as a 

 further oxidation is here not effected : 



OBERMA YER'S TEST. A few cubic centimeters of urine are treated 

 with an equal volume of a 2 pro mille solution of ferric chloride in 

 concentrated hydrochloric acid. The indigo-blue is extracted, as 

 above, by shaking with a little chloroform. As in the above test, 

 indoxyl-red may thus also be obtained, and is separated from the 

 blue pigment as just described. 



Test for Urohaematin (so-called). A small amount of urine is thor- 

 oughly agitated with chloroform and allowed to stand for a few 

 days. The chromogen of indoxyl-red is thus extracted, for on adding 

 a drop of concentrated hydrochloric acid to the chloroform extract 

 a beautiful rose-color appears, which varies in intensity with the 

 amount of the chromogen present. In normal urine a faint reaction 

 only is usually seen ; but in disease, and notably in ileus, peritonitis, 

 and cancer of the stomach, I have repeatedly met with more indigo- 

 red than indigo-blue. 



ROSENBACH'S REACTION. This reaction is mostly obtained under 

 pathological conditions, and indicates the existence of greatly in- 

 creased intestinal putrefaction. It is referable to the simultaneous 

 formation of indigo-red and indigo-blue. 



AVhile boiling, a few cubic centimeters of urine are treated drop 

 by drop with concentrated nitric acid containing a little nitrous 

 acid, when in the presence of much indigo-red, viz., its chromogen, 

 the urine assumes a dark Burgundy color, and usually shows a 

 bluish tint when held to the light. On standing, the red pigment 

 is precipitated. If much indigo-blue is present at the same time, 

 as is usual, the foam of the liquid is colored blue. On adding an 

 excess of the acid the color often disappears and the urine turns 

 yellow. 



