246 



THE LIVER. 



it remains in the gall-bladder. Analysis will, therefore, vary 

 materially, according as the secretion is removed through a fistula 

 of the bile-duct, in which case it would come directly from the 

 liver or from the gall-bladder after having been stored there for 

 some time. 



The table on page 246 gives the results of various analyses of 

 bile which have been made by competent chemists. 



Bile-pigments. These are two : bilirubin and biliverdin. Both 

 of these are present in bile, but if the color is of a reddish brown, 

 as in the carnivora, the bilirubin predominates, while the predomi- 

 nance of the biliverdin gives the greenish hue, the characteristic 

 color of the bile of the herbivora. The formula for bilirubin 

 is C 16 H 18 N 2 O 3 , or, as given by some writers, C 32 H 36 N 4 O 6 ; that of 

 biliverdin, C 16 H 18 N 2 O 4 or C 32 H 36 N 4 O 8 i. e., the former passes into 



Composition of Normal Human Bile. 



the latter by oxidation. It is because of a reduction in the bili- 

 verdin that the greenish color of fresh human bile becomes red- 

 dish after it has remained for some time in the gall-bladder. 



In clots of blood that are old, crystals are found to which the 

 name hematoidin was given by Virchow. This is identical with 

 bilirubin. Indeed, it is now conceded that the pigments of the 

 bile are derived from hemoglobin, the coloring-matter of the blood. 

 Thus one of the functions of the liver-cells is to change the 

 hemoglobin which comes from broken-down red blood-corpuscles 

 to bile-pigment, separating from it the iron and preserving it for 

 future blood-making. 



Neither bilirubin nor biliverdin shows any absorption-bands 

 with the spectroscope. 



Gmelin's Test for Bile-pigment. If diluted bile, or a solution 

 containing bile-pigment, is poured into fuming nitric acid i. e., 

 nitric acid containing nitrous acid, which is a powerful oxidizing 

 agent there will be produced a set of rings or zones of different 

 colors, according to the amount of oxidation of the bilirubin. The 



