CONSTITUENTS OF THE BILE. 355 



neutral reaction. The specific gravity of human bile from the gall- 

 bladder = 1026-1032, while that from a fistula = 1010-101 1 (Jacobsen). 

 It contains: 



(1.) Mucus, which gives bile its sticky character, and not unfre- 

 quently makes it alkaline, is the product of the mucous glands and the 

 goblet-cells of the mucous membrane of the larger bile-ducts. When 

 bile is exposed to the air, the mucus causes it to putrefy rapidly. It is 

 precipitated by acetic acid, or alcohol. [Bile from the gall-bladder, 

 when poured from one vessel into another, shows the presence of mucin 

 in the form of thin threads connecting the fluids in the two vessels. 

 When such bile is treated with alcohol, it no longer exhibits this 

 property, but flows like a non-viscid watery fluid. The bile formed in 

 the ultimate bile-ducts does not seem to contain muciu or mucus, but 

 bile from the gall-bladder always does.] 



(2.) The Bile Acids. Glycocholic and taurocholic acids, so-called 

 conjugate acids, are united Avith soda (in traces with potash) to form 

 glycocholate and taurocholate of soda, which have a bitter taste. In 

 human bile (as well as in that of birds, many mammals, and amphibians), 

 taurocholic acid is most abundant; in other animals (pig, ox) glyco- 

 cholic acid is most abundant. These acicls rotate the plane of polarised 

 light to the right. 



((/.) Glycocholic acid, C 26 H 43 N0 6 (first discovered and described as 

 cholic acid by Gmelin, and called, by Lehmann, glycocholic acid). 

 When boiled with caustic potash, or baryta Avater, or Avith dilute 

 mineral acids, it takes up H 2 (Strecker, 1848), and splits into 



Glycin ( = Glycocoll = Gelatin Sugar = Amidoacetic acid) =C 2 H 5 N0 2 . 

 + Cholalic acid (also called Cholic acid) . . . =C 2 4H 40 5 . 



= Glycocholic acid + Water . . =C 2C H4 3 NO G + H 2 0. 



(b.) Taurocholic acid, Co G H 45 ]S[S0 7 , Avhen similarly treated, takes 

 up Avater and splits into 



Taurin (= Amidonethyl-sulphuric acid) = C 2 

 + Cholalic acid .... =C 



= Taurocholic acid + Water . . =C 2 6H 45 NS07 + H 2 (Strecker). 



Preparation Of the Bile acids. Bile is evaporated to ^ of its volume, rubbed 

 up into a paste with excess of animal charcoal, and dried at 100C. The black 

 mass is extracted with absolute alcohol, which is filtered until it is clear. After a 

 part of the alcohol has been removed by distillation, the bile salts are precipitated 

 in a resinous form, and on the addition of excess of ether, there is formed immedi- 

 ately a crystalline mass of glancing needles (Platner's "crystallised 6-ife"). The 

 alkaline salts of the bile acids are freely soluble in water or alcohol, and insoluble in 

 ether. Neutral lead acetate precipitates the glycocholic acid as lead glycocholate 

 from the solution of both salts ; the precipitate is collected on a filter, dissolved 

 in hot alcohol, and the lead is precipitated as lead sulphide by H 2 S ; after removal 

 of the lead sulphide, the addition of water precipitates the isolated glycocholic 

 acid. If, after precipitating the lead glycocholate, the filtrate be treated with 



