THE CONSTITUENTS OF BILE 429 



II. THE CONSTITUENTS OF BILE. 



The constituents of the bile are : 



(1) The colouring matters, bilirubin and biliverdin, the latter formed 

 by the oxidation of the former. 



(2) The bile salts, the sodium salts of glycocholic and taurocholic 

 acids. 



(3) A small quantity of mucin or nucleoprotein (the more recent work 

 insists on the presence of the latter, but both are probably present). 



(4) Cholesterol, which gives rise to gall-stones in certain conditions. 

 Examination of Ox or Sheep Bile. 



(1) It has a faintly alkaline reaction to litmus ; the bitter taste 

 and peculiar odour should be noticed. 



(2) It does not coagulate on heating. 



(3) On acidifying a small quantity with acetic acid a precipitate is 

 formed which is insoluble in excess of acetic acid. As above stated, 

 this precipitate was considered to be mucin owing to its insolubility in 

 excess of acid, nucleoprotein being soluble ; in the presence of bile 

 salts the precipitate of nucleoprotein is insoluble. 



(3#) No pigrnent is extracted on shaking up a little bile with ether. 

 If a few drops of dilute hydrochloric acid be added, both nucleoprotein 

 and pigment are liberated as free acids from their sodium compounds. 

 The nucleoprotein is precipitated, but the pigment passes into solution 

 on shaking with the ether. 



(4) Gmelin's Test for Bile Pigments. A little bile is carefully 

 placed on the surface of some fuming nitric acid in a test tube, either 

 by pouring it carefully down the side of the tube or by means of a 

 pipette. On shaking the tube very gently a play of colours will be 

 seen as the bile becomes oxidised. Generally the colours are yellow, 

 red, violet, blue, green ; 



or, 



A drop of fuming nitric acid is placed on a thin film of bile in a 

 porcelain basin. Rings of the various colours will be seen ; 



or, 



A little bile is filtered several times through an ordinary filter paper 

 and a drop of fuming nitric acid is placed on the paper. The colours will 

 be seen. 



(5) Huppert's Test for Bile Pigments. This test is especially 

 useful for detecting bile pigments in urine. 



5 c.c. of bile are diluted with 25-50 c.c. of water and 4 cc. 

 of sodium phosphate solution and 6 c.c. of calcium chloride solution 

 are added. The precipitate is filtered off. It carries down the pigment 

 mechanically or may contain an insoluble calcium compound of bili- 

 rubin ; it is heated with 5 c.c. of alcohol and a few drops of concentrated 

 hydrochloric acid. A fine green colour is formed. The formation of 

 the green colour may require the addition of an oxidising agent such 

 as $ fe\y drops of ferric chloride or potassium chlorate solution (Cole). 



