THE BILE. 175 



Pure biliverdin, like bilirubin, gives no characteristic band of 

 absorption in alkaline solution. In acid solution, however, or in 

 pure alcoholic solution, an indistinct band is observed at D, and one 

 that is more pronounced near F. 



The substance is amorphous, or at least cannot be obtained in a 

 pronounced crystalline form. 



On reduction, biliverdin is supposedly transformed into bilirubin, 

 though this is denied by some observers. 



On oxidation with nitric acid biliverdin gives rise to the various 

 colors which have already been described, beginning with blue. It 

 gives Huppert's reaction directly. 



Isolation. To prepare biliverdin, it is most convenient to start 

 with a solution of bilirubin in the form of its sodium salt which has 

 been exposed to the air until the original golden-yellow color has 

 changed to a brownish green. The biliverdin is then precipitated 

 by adding an excess of hydrochloric acid. It is filtered off, washed 

 free from all acid, dissolved in absolute alcohol, and precipitated by 

 .copiously diluting with water. Any bilirubin that may be present 

 is removed by extracting with chloroform. 



Biliprasin. Biliprasin as such, and biliprasinate of sodium, ac- 

 cording to Dastre and Floresco, are also found in normal bladder- 

 bile, and, as has been indicated, represent intermediary products of 

 oxidation between bilirubin and biliverdin. 



The sodium salt, according to these observers, is a yellowish-brown 

 pigment, and can be transformed into biliprasin through the agency 

 of mineral acids, of acetic acid, and even of carbonic acid. On ex- 

 posure to the air it passes over into the corresponding biliverdinate. 

 To its presence the yellow color of the bile of calves and of other 

 animals is supposedly due. 



Biliprasin itself is green, but can be transformed into the yellow 

 salt by adding a few drops of an alkali, and this in turn yields the 

 green pigment on treating with an acid. This reaction, according 

 to Dastre and Floresco, explains the fact that yellow bile can become 

 green without oxidation, viz., without the formation of biliverdin. 

 According to older ideas, however, biliprasin is an oxidation-product 

 of biliverdin, and is supposed to result from this with the inter- 

 mediary formation of bilifuscin, as has already been outlined. 



Bilifuscin is said to occur in gall-stones together with bilirubin. 

 The formula which has been ascribed to it is that of bilirubin plus 

 one or two molecules of water, viz., C 32 H 40 N 4 O 8 or C 16 H 20 N 2 O 4 . It 

 is of a dark-brown color, and is soluble in alcohol and the solutions 

 of the alkaline hydrates, but insoluble in water and chloroform. 

 In pure form it does not give Gmelin's reaction. 



Bilicyanin, or cholecyanin, is the blue pigment which is formed 

 during the oxidation of bilirubin and biliverdin with nitric acid. It 

 has been found together with the common bile-pigments in gall- 

 stones taken from man. Its neutral and alkaline solutions give rise 

 to three bands of absorption. One of these is located between C 



