316 THE CONSTITUENTS OF THE BILE. 



glycocholic acid predominates; in carnivora, the sheep, the goat, tauro- 

 cholic acid. 



(a) Glycocholic acid, C 26 H 43 NO 6 , is decomposed by boiling with potas- 

 sium or barium hydrate or with dilute mineral acids, and by taking 

 up water splits into 



C 2 H 5 N0 2 + C 24 H 40 5 = C 26 H 43 N0 6 + H 2 O 



Glycin (glycocoll, + Cholalic or = Glycocholic Acid -f- Water, 

 gelatin-sugar, amido- cholic Acid 



acetic acid) 



(b) Taurocholic acid, C 26 H 45 NSO 7 , decomposes with similar treatment 

 and addition of water into 



C 2 H 7 NS0 3 + C 24 H 40 5 C 26 H 45 NSO ? + H 2 O 



Taurin (amido-ethyl- + Cholic Acid = Taurocholic Acid + Water. 

 sulphuric acid, pris- 

 matic crystals) 



Demonstration of the Biliary Acids. The bile is evaporated to one-fourth its vol- 

 ume, triturated to a pasty mass with animal charcoal to remove the coloring- 

 matter, and dried at 100 C. The black mass is extracted with absolute alcohol, 

 which passes colorless through the filter. After a portion of the alcohol has been 

 driven off by evaporation, the addition of an excess of ether causes at first a 

 resinoid precipitate of salts of the biliary acids, which later pass over into a crys- 

 talline mass of brilliant needles (Platner's crystallized bile) . The alkaline salts of 

 the biliary acids obtained in this way are readily soluble in water or alcohol, but 

 are insoluble in ether. From the solution of both salts neutral lead acetate pre- 

 cipitates a portion of the glycocholic acid as lead glycocholate. The latter is 

 collected on a filter, dissolved in hot alcohol, and lead sulphid is precipitated by 

 hydrogen sulphid. After removal of the precipitate, the addition of water causes 

 separation of the isolated glycocholic acid. If, after precipitation of the lead 

 glycocholate, basic lead acetate is added to the filtrate, a" precipitate of lead 

 taurocholate forms, uncontaminated, however, by lead glycocholate, from which 

 the free acid is subsequently obtained by analogous treatment. 



According to Schotten and others, human bile contains, in addition to cholic 

 acid, still another acid, fellic acid (C 2 ,H M O 4 ) ; the bile of cattle contains cholic 

 acid(C 24 H 40 5 ). 



Of the products of decomposition of the biliary acids, glycin does not occur 

 as such in the body, but only in the bile in combination with cholic acid, in the 

 urine in combination with benzoic acid as hippuric acid, and finally in gelatin 

 in. complete combination. 



Cholic acid is dextrorotatory, insoluble in water, soluble in alcohol; it is 

 soluble with difficulty in ether, separating out in prisms. Its crystalline alkaline 

 salts are readily soluble in water, like soap. With iodin, in direct light, it yields 

 a yellow, in transmitted light a blue, crystalline combination. It occurs free only 

 in the intestine. 



Cholic acid is replaced in the bile of some animals by a related acid, as, 

 for example, in the bile of swine, by hyocholic acid; in the bile of geese, chenocholic 

 acid is present. 



By boiling with concentrated hydrochloric acid or heating, dry, to 200 C., 

 cholic acid is changed into an anhydrid dyslysin. 



Dyslysin is only an artificial product and never occurs in the intestines. When 

 fused with potassium hydrate, it is changed back to potassium cholate. 



Pettenkofer's Test. The biliary acids, the cholic acids and their anhydrids, 

 when dissolved or broken up in water, and on addition of two-thirds concentrated 

 sulphuric acid (drop by drop, without permitting the temperature of the fluid to 

 rise above 70 C.), and a few drops of a 10 per cent, solution of cane-sugar, yield 

 a purplish-red transparent color, which shows two absorption-bands in the spec- 

 trum, at E and F. 



Before examining a solution for the presence of biliary acids, the albumin must 

 always be first removed, as the latter yields a similar reaction, although the red 

 solution here is characterized by only one absorption-band. If only small amounts 

 of biliary acids are present, the fluid must first be concentrated by evaporation. 

 Cholesterin, stearic and oleic acids, as well as phenol and pyrocatechin, exhibit 

 a similar reaction. Pettenkofer's test, therefore, is absolutely reliable only when 



