TESTS FOB BILE. 275 



the blood of the portal system. The ingredients of the bile 

 which it is important to detect are biliverdine, the biliary 

 salts, and cholesterine. The last-named substance can be 

 detected best by applying the method which we have just 

 described for its extraction ; but several tests have been pro- 

 posed for the detection, on the one hand, of the coloring 

 matter of the bile, and on the other, of the peculiar, biliary 

 salts. 



Test for Biliverdine. There is one test so simple and 

 easy of application, that it alone will suffice for the prompt 

 detection of biliverdine. This is peculiarly applicable to 

 the urine, where the presence or absence of bile frequently 

 becomes an important question. 



We are led generally to suspect the presence of bile in 

 the fluids of the body by the peculiar color. If we spread 

 out the suspected fluid in a thin stratum upon a white sur- 

 face, as a porcelain plate, and add a single drop of nitric acid, 

 or, what is better, nitroso-nitric acid, if the coloring matter 

 of bile be present, a peculiar play of colors will be observed 

 at the circumference of the drop of acid as it diffuses itself. 

 The color will rapidly change from blue to red, orange, 

 purple, and finally yellow. This is due to the action of the 

 acid upon the biliverdine ; and this test will not indicate the 

 presence of either cholesterme or the biliary salts. It is 

 used, therefore, only when we wish to determine the presence 

 of the coloring matter of the bile. 



Test for the Biliary Salts. The best, and, indeed, the 

 only reliable test for the biliary salts, was proposed many 

 years ago by Pettenkofer, 1 and is now generally known as 

 Pettenkofer's test. This requires some care and practice in 

 its application, but it is entirely reliable ; and although it 

 has been objected that there are other substances than the 



1 PETTENKOFER, Notiz uber eine neue Reaction auf Galle und Zucker.An- 

 nalen der Chemie und Pharmacie, Heidelberg, 1844, Bd. Hi., S. 90. 



