THE BILE. 165 



Isolation. Taurocholic acid is most conveniently obtained from 

 Platner's bile of man or the ox, as already described. To isolate 

 it from the bile of dogs, the fluid is shaken with animal charcoal 

 and alcohol, then decanted and filtered. The filtrate is evaporated 

 to dryness, the residue taken up with a small amount of warm 

 absolute alcohol, and filtered. The clear solution is then treated 

 with ether until it becomes cloudy. On standing, the taurocholate 

 of sodium separates out in the form of fine crystals. These are 

 dissolved in water and treated with ammoniacal subacetate of lead. 

 The resulting precipitate is suspended .in alcohol and decomposed 

 with hydrogen sulphide. The free acid is thus liberated, and can 

 be obtained as such by evaporating the filtrate to dryness or by 

 diluting with ether. 



To isolate chenotaurocholic acid, the bile of geese is first treated 

 with strong alcohol, to remove the mucus. The filtrate is mixed 

 with ether and set aside, when the biliary salts separate out as 

 a glutinous mass, which is then washed, dried, redissolved in 99 per 

 cent, alcohol, and again precipitated with ether. The crystalline 

 deposit which is formed is dissolved in strong alcohol and decom- 

 posed with hydrogen sulphide. On evaporation the free acid is 

 obtained. 



Gholalic Acid. Cholalic acid is the principal biliary acid which 

 is formed in the liver, and to its presence in the molecule of glyco- 

 cholic acid and taurocholic acid Pettenkofer's reaction is due. It is 

 a product of the specific activity of the liver-cells, and is normally 

 not found in any other tissues or organs of the animal body. In 

 the intestinal contents, however, it may be encountered, as such, 

 even in health, and in cases of jaundice it has been observed also in 

 the urine. Its artificial introduction in dogs leads to an increased 

 elimination of taurocholic acid. This is temporary, and ceases when 

 the taurin, which lias been stored in the liver, is exhausted. 



As I have already shown, cholalic acid is liberated when glyco- 

 cholic acid or taurocholic acid is decomposed with alkalies or acids, 

 under the application of heat. Its crystalline form differs accord- 

 ing to the medium in which crystallization has taken place. From 

 its alcoholic solution it separates out in the form of rhombic 

 tetrahedra or octahedra, which contain one molecule of alcohol as 

 liquid of crystallization, C 24 H 40 O 5 + C 2 H 6 O. On prolonged boiling 

 with water the crystal-alcohol can be removed. When dissolved in 

 dilute boiling acetic acid cholalic acid takes up one molecule of 

 water, and can be obtained from such solutions in the form of 

 rhombic plates or prisms, C 24 H 40 O 5 .H 2 O. On exposure to the air 

 the crystals in either case soon become opaque. They melt at a 

 temperature of 195 C. The free acid is readily soluble in alcohol, 

 with difficulty so in water, and is almost insoluble in ether. 



According to Mylius, it is a monobasic alcoholic acid, and contains 

 one secondary and two primary alcoholic groups, as represented by 



