I 54 PHYSIOLOGICAL CHEMISTRY. 



conditions. Biliverdin may be obtained in the form of a green 

 powder. In common with bilirubin, it may be converted into hy- 

 drobilirubin by nascent 'hydrogen. 



The neutral solution of bilicyanin or cholecyanin is bluish-green 

 or steel-blue and possesses a blue fluorescence, the alkaline solution 

 is green with no appreciable fluorescence and the strongly acid so- 

 lution is violet-blue. The alkaline solution exhibits three absorp- 

 tion-bands, the first a dark, well-defined band between C and D, 

 somewhat nearer C ; the second a less sharply-defined band extend- 

 ing across D and the third a rather faint band between E and F, 

 near E (Absorption Spectra, Plate II). The strongly acid so- 

 lution exhibits two absorption bands, both lying between C and E 

 and separated by a narrow space near D. A third band, exceed- 

 ingly faint, may ordinarily be seen between b and F. 



Biliary calculi, otherwise designated as biliary concretions or 

 gall stones, are frequently formed in the gall-bladder. These de- 

 posits may be divided into three classes, cholesterol calculi, pigment 

 calculi and calculi made up almost entirely of -inorganic material. 

 This last class of calculus is formed principally of the carbonate and 

 phosphate of calcium and is rarely found in man although quite 

 common to cattle. The pigment calculus is also found in cattle, 

 but is more common to man than the inorganic calculus. This 

 pigment calculus ordinarily consists principally of bilirubin in com- 

 bination with calcium; biliverdin is sometimes found in small 

 amount. The cholesterol calculus is the one found most frequently 

 in man. These may be formed almost entirely of cholesterol, in 

 which event the color of the calculus is very light, or they may con- 

 tain more or less pigment and inorganic matter mixed with the 

 cholesterol, which tends to give us calculi of various colors. 



For discussion of cholesterol see page 250. 



EXPERIMENTS ON BILE. 



1. Reaction. Test the reaction of fresh ox bile to litmus. 



2. Nucleoprotein. Acidify a small amount of bile with dilute 

 acetic acid. A precipitate of nucleoprotein forms. 



3. Inorganic Constituents. Test for chlorides, sulphates and 

 phosphates (see page 57). 



4. Tests for Bile Pigments, (a) Gmelin's Test. To about 

 5 c.c. of concentrated nitric acid in a test-tube add 2-3 c.c. of diluted 

 bile carefully so that the two fluids do not mix. At the point of 

 contact note the various colored rings, green, blue, violet, red and 



