384 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



While the bile is entirely free from proteicls, it contains both organic 

 and inorganic constituents. The former group are represented by mucin, 

 a compound of sodium with two organic acids (glycocholic and tauro- 

 cholic), a coloring matter which undergoes various modifications and 

 whose origin is a source of considerable interest, lecithin, small quanti- 

 ties of fat and soap, and a small amount of diastatic ferment. These will 

 be considered in turn. 



(a) Mucin. Mucin gives to bile its viscidity, and is the product of 

 the mucous glands of the larger bile-ducts and gall-bladder. The longer 

 the bile remains in the gall-bladder, the larger will be the percentage of 

 mucin found in it, since the mucous cells in the walls of this reservoir 

 are the principal sources of this bod} 7 . In the bile of animals supplied 

 with a gall-bladder, mucin will be found in larger amounts than in ani- 

 mals in whom this appendage to the liver, as in the case of the horse, is 

 absent. The smaller bile-ducts are free from mucous cells, and, as a con- 

 sequence, bile coming directly from the liver-cells contains no mucin. 

 The longer the gall remains in the gall-bladder, the more will it deviate 

 from its general character when freshly secreted by the liver-cells. Yel- 

 low bile gradually becomes greenish, and its consistence will become 

 more marked from the addition of mucus. The general characteristics 

 of mucin found in the bile do not differ from those of mucin found else- 

 where. It may be precipitated by acetic acfd, and when bile containing 

 mucus is precipitated with alcohol it loses its viscidity. 



(b) The Bile Acids. The bile acids occur in the bile in the form of 

 compounds with sodium, and occasionally with minute amounts of potas- 

 sium, to form glycochplate and taurocholate of sodium, two salts which 

 are highly soluble in water. The relative proportions of these two salts 

 vary considerably in the ,bile of many animals. In that of man, as well 

 as of birds, many mammals and amphibia, taurocholic acid is most 

 abundant. In other mammals, as in the pig and ox, sodium gtycocko- 

 late is in largest amount, while the taurocholate is more scanty. In the 

 bile of the dog, cat, bear, and other carnivora, taurocholate is almost the 

 sole representative of these salts, while the glycocholate is almost entirely 

 absent. In the bile of the pig, in addition to these two salts, the hyocho- 

 late of sodium is also present. 



The gall of the hog contains, besides hyoglycocholic acid, another until 

 lately unknown acid, which occurs in larger quantity than the first known acid 

 (Jolin). It is, for the present, called B-hyoglycocholic acid. It is with difficulty 

 obtained pure, as neither it nor its salts are crystallizable. It is distinguished 

 from the A-acid by its behavior with saturated sodium sulphate solution, which 

 precipitates the sodium salt of the A-acid almost completely, and in a flocculent 

 Ibrin, whereas the sodium salt of the B-acid is only partly precipitated, and is 

 at first colored, and easily soluble in water. The purified salt is separated 

 from the alcoholic solution by means of ether, as a snowy-white, cheesy precipi- 

 tate, which soon shrinks to a yellowish mass, whereby much ether is pressed out. 

 This mass is easily soluble in water and alcohol, and the solutions allow them- 



