BILE PIGMENTS. 125 



the color of the fasces is due principally to the hydrobili- 

 rubin. Bilirubin is acted upon by oxidizing agents, with 

 the formation of biliverdin. This change takes place when 

 an alkaline solution is left exposed to the air. 



Biliverdin is an amorphous, green powder. It differs 

 from bilirubin in being insoluble in chloroform, and the 

 two can consequently be separated by this reagent. 



Both of these biliary pigments when acted upon by 

 yellow nitric acid, such as is formed by allowing the strong 

 acid to stand in a bright light, undergo a change of color 

 through green, blue, violet, and red to yellow. 



Besides these two coloring matters a number of others 

 have been described by different authors. Of them com- 

 paratively little is known. They appear to be derived from 

 biliverdin and bilirubin, and it is to their formation that 

 the play of colors is due when bile is acted upon by oxid- 

 izing agents. Some of these are: 



Biliprasin, greenish black. 



Bilifuscin, brown. 



Bilicyanin, blue. 



Choletelin, yellow to brown. 



Not infrequently there are found in the gall-bladder con- 

 cretions, commonly known as gall-stones. They are sometimes 

 nearly as large as a hen's egg, and may fill the bladder almost com- 

 pletely. They are soft and often worn away from rubbing against 

 one another. If they are cut through the nucleus is generally 

 found to be dark colored and composed of bilirubin- calcium. 

 Around this are concentric layers, usually of eholesterin, but some- 

 times of the bilirubin-calcium. Calcium carbonate is also found in 

 the concretions, as well as others of the biliary pigments in smaller 

 amounts. 



266. SEPARATION or THE SALTS or THE BILIARY 

 ACIDS. The contents of the gall-bladder of an ox should 

 be mixed with washed sand and evaporated to dryness on 



