EXAMINATION OF NORMAL AND ABNORMAL URINE. 475 



The further detection of bile depends upon the reactions of the 

 biliary coloring matters or biliary acids; it frequently happens, 

 however, that the pigments are present, whilst the acids are not. 



Gmelin's test for biliary coloring matters has been considered al- 

 ready, and may be applied to urine either by allowing a small quan- 

 tity of nitric acid, containing some nitrous acid, to flow down the sides 

 of a test-tube (containing the urine) in such a manner that the two 

 fluids do not mix, or by placing upon a porcelain plate a few drops 

 of the urine, near it a few drops of nitric acid, to which one drop of 

 sulphuric acid has been added, and allowing the two liquids to ap- 

 proach gradually. In both cases (if bile pigment is present) a play of 

 color is seen at the point of union between the two fluids, the colors 

 changing from green to blue, violet-red, and yellow or yellowish- 

 green. While the appearance of the green at the beginning is indis- 

 pensable to prove the presence of bile, the presence of all the other 

 colors is not essential. (Plate VIII., 7.) 



The above test may be made in a somewhat modified form by mix- 

 ing the urine with a concentrated solution of sodium nitrate, and 

 pouring down the sides of the test-tube concentrated sulphuric acid in 

 such a manner as to form two distinct layers ; the colors are seen at 

 the point of contact as above. 



If the urine be very dark in color, it should be diluted with water 

 before applying the above tests. 



Ultzmann's test for bile pigment is made by mixing 10 c.c. of urine 

 with 3 or 4 c.c. of potassium hydroxide solution (1 in 3 of water), 

 and supersaturating with hydrochloric acid ; the mixture assumes a 

 beautiful emerald-green color after some time. 



Pettenkofer' 's test for biliary acids is made by dissolving a few grains 

 of cane-sugar in urine contained in a test-tube, and allowing some 

 concentrated sulphuric acid to trickle down the side of the inclined 

 test-tube ; a purple band is seen at the upper margin of the acid, and 

 on slightly shaking the liquid becomes at first turbid, then clear, and 

 almost simultaneously it turns yellow, then pale cherry-red, dark car- 

 mine-red, and finally a beautiful purple violet. The temperature 

 must not be allowed to rise much above 38 C. (100 F.) (Plate 

 VIII., 8.) 



As many substances (other than biliary acids) show a similar 

 reaction, it is often necessary to separate the bile acids by the process 

 described in connection with the consideration of bile itself. 



In case the quantity of biliary constituents is so small that they 

 cannot be noticed by the tests mentioned, the urine should be shaken 



