DISEASES OF THE LITER. 



diagnosis between jaundice and other discoloratious. The yellow tint 

 of the skin and solera completely disappears by artificial light, so that 

 we cannot recognize jaundice at night. We may see that the exter- 

 nal mucous membranes are also yellow, by pressing the blood from the 

 lips or gums of a patient with jaundice ; when the finger is removed, 

 the spot left will not be white, but yellow. Sometimes the urine is 

 light brown, like thin beer, sometimes dark, like porter ; after stand- 

 ing in the air, it almost always becomes greenish. If we agitate the 

 discolored urine, its froth is distinctly yellow, and a strip of linen or 

 white paper dipped in it becomes yellow, and this often suffices to dis- 

 tinguish between the coloring matter of the bile and other coloring 

 matter hi the urine. The test with nitric acid containing some nitrous 

 acid is more certain. On adding this, the brown of the bile-coloring 

 matter successively becomes green, blue, violet, red, and finally pale 

 yellow. To note the changes well, we should carefully let some of 

 the acid run down the inside of a champagne or test glass, containing 

 the urine to be tested, so that it will reach the bottom, and there will 

 be only a gradual admixture of the acid with the urine. If there be 

 any bile-coloring matter present, and we let the urine stand a while, 

 the various layers immediately above the nitric acid show different 

 colors, and the above series of colors may be perfectly or partly dis- 

 tinguished from above downward. The reaction may be incomplete, 

 or may fail entirely, if the urine has stood exposed to the air for some 

 time, and already has a greenish color. According to Frerichs, the 

 opposite occurs occasionally ; the reaction does not take place till the 

 urine has stood in the air for some time ; until quite recently the oc- 

 currence of the bile-acids in the urine during icterus has been denied 

 by celebrated authorities. There are certain difficulties in their detec- 

 tion in jaundiced urine by Pettenkofer's test, which shows very small 

 quantities of the bile-acids by inducing a purplish-red color, when to 

 the solution containing them we add a small amount of sugar, and 

 then gradually add concentrated sulphuric acid. This reaction cannot 

 be directly used when the fluid to be examined, as the urine, also con- 

 tains substances which are directly colored by the addition of sulphuric 

 acid. Hoppe-Seyler deserves the credit of having disproved the erro- 

 neous belief that in jaundice the urine contained only the coloring 

 matter of the bile, and not the bile-acids, and of having proved the 

 presence of the latter in the jaundiced urine by a complicated but per- 

 fectly reliable process. 



Bile-pigment constantly occurs in the sweat also, so that the linen 

 is colored yellow, particularly at those parts where the patients sweat 

 much. The milk of nursing-women has also been found colored yellow 



The moat noticeable change hi the faeces, from obstruction to the 



