THE BILE PIGMENTS. 357 



acid, until the fluid is syrupy, then add the cane-sugar, and afterwards place the 

 whole in boiling water. When investigating the amount of bile acids in a liquid, 

 the albumin must be removed beforehand, as it gives a reaction similar to the 

 bile acids, but in that case the red fluid has only one absorption-band. If only 

 small quantities of bile acids are present, the fluid must in the first place be 

 concentrated by evaporation. 



The origin of the bile acids takes place within the liver. After its 

 extirpation, there is no accumulation of biliary matters in the blood 

 (Joh. Miiller, Kunde, Moleschott). 



How the formation of the nitrogenous bile acids is effected is quite unknown. 

 They must be obtained from the decomposition of albuminous materials, and it is 

 important to note that the amount of bile acids is increased by albuminous food. 



Taurin contains the sulphur of albumin ; bile salts contains 4- 4 '6 p.c. of sulphur 

 (Voit), which may perhaps be derived from the stroma of the dissolved red blood - 

 corpuscles. 



(3.) The Bile Pigments. The freshly secreted bile of man and many 

 animals has a yellowish-brown colour, due to the presence of bilirubin 

 (Stadler). When it remains for a considerable time in the gall-bladder, 

 or when alkaline bile is exposed to the air, the bilirubin absorbs and 

 becomes changed into a green pigment, biliverdin. This substance is 

 present naturally, and is the chief pigment in the bile of herbivora 

 and cold-blooded animals. 



(a.) Bilirubin (C 32 H 36 N 4 6 ) is, according to Stadler and Maly, 

 perhaps united with an alkali; it crystallises in transparent fox-red 

 clinorhombic prisms. It is insoluble in water, soluble in chloroform, by 

 which substance it may be separated from biliverdin, which is in- 

 soluble in chloroform. It unites as a monobasic acid with alkalies, and 

 as such is soluble. It is identical with Virchow's haematoidin 

 (p. 35). 



Preparation. It is most easily prepared from the red (bilirubin-chalk) gall- 

 stones of man or the ox. The stones are pounded, and their chalk dissolved 

 by hydrochloric acid ; the pigment is then extracted with chloroform. 



That bilirubin is derived from haemoglobin is very probable, considering its 

 identity with hsematoidin. Very probably red blood-corpuscles are dissolved in 

 the liver, and their haemoglobin changed into bilirubin. 



(6.) Biliverdin (Heintz), C 32 H 36 N 4 8 , is simply an oxidised derivative 

 of the former, from which it can be obtained by various oxidation 

 processes. It is readily soluble in alcohol, very slightly so in ether, 

 and not at all soluble in chloroform. It occurs in considerable 

 amount in the placenta of the bitch. As yet it has not been retrans- 

 formed by reducing agents into bilirubin. 



Tests for Bile Pigments. Bilirubin and biliverdin may occur in 

 other fluids e.g., the urine, and are detected by the Gmelin-Heintz' 

 reaction. When nitric acid containing some nitrous acid is added to the 

 liquid containing these pigments, a play of colours is obtained, begin- 

 ning with green (biliverdin), blue, violet, red, ending with yellow. 



