386 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



and allowed to dry. Dropping a little sulphuric acid on the paper thus prepared 

 will in a few seconds produce a violet-red color. Proteids will also behave in the 

 same way as Platner's crystallized bile, but the reactions may be distinguished by 

 the fact that, when examined spectroscopically, two absorption bands, one near the 

 line E and the other opposite F, will be found when the bile is examined, and will 

 be absent from the color produced by this test with albuminoids. Amylic alcohol 

 will also produce a similar reaction, and here again the spectroscope will serve to 

 distinguish them. This test depends upon the fact that cholic acid is first pre- 

 cipitated by sulphuric acid in a whitish form, as may be readily seen in solutions 

 of crystallized bile, and then dissolved, assuming a cherry-red color, which 

 becomes gradually darker in hue. The pigments and, to a still more marked 

 degree, the presence of nitrates or chlorates will interfere with this reaction. 



The source of the biliary acids is almost unknown, except that they 

 probably originate from the breaking down of albuminoids. They are 

 not found in the blood, but are formed in the hepatic cells, the nitrogen 

 possibly originating from the albuminoid, while the cholic acid radical 

 may be derived from the fats. These acids are compounds of taurin and 

 glycochol with cholic acid, into which they may readily be split up by 

 prolonged boiling with alkalies or mineral acids. 



Glycocholic Acid (C 26 ~rI„N0 6 ).— Glycocholic acid occurs in large 

 amounts in the bile of herbivora, while it is only found in small quantities 

 in the bile of carnivora and omnivora. It originates from the union of 

 glycochol with cholic acid, and, like taurocholic acid, is closely allied to 

 hippuric acid. When boiled with hydrochloric acid it is decomposed 

 into glycochol and cholic acid, the latter being a non-nitrogenous body. 

 The reaction is as follows : — 



C 26 H 43 NO 6 +H 2 O = C 24 H 40 O 5 + C 2 H 5 NO 2 . 

 Glycocholic Acid. Water. Cholic Acid. Glycochol. 



Glycocholic acid crystallizes in glistening, white needles, which are 

 almost insoluble in cold water, slightly soluble in hot water, easily 

 soluble in alcohol, and slightly soluble in ether. 



Taurocholic Acid (C 26 H„NO,S). — Taurocholic acid is the only acid 

 in dog's bile, as in that of other carnivora, though it can be obtained in 

 small amounts from ox-gall after the removal of glycocholic acid. It 

 contains sulphur, and forms white, glistening needles, which become 

 fluid when in contact with the air. Taurocholic acid is soluble in water 

 and alcohol and insoluble in ether. Of these acids only the alkaline 

 salts are soluble in alcohol and water. Out of a mixture of glycocholic 

 and taurocholic acid salts, acetate of lead will precipitate the glycocholic 

 acid as a glycocholate of lead. When filtered off, the addition of acetate 

 of lead and ammonia will precipitate taurocholic acid as a taurocholate 

 of lead, which may be easily dissolved in hot alcohol, and the lead 

 removed by passing a current of sulphuretted hydrogen through it. 



Taurocholic acid originates in the breaking down of albuminoids, 

 from which the sulphur is derived, and its amount in the bile may be 



