386 FOOD AND DIGESTION 



The gall-bladder, g. bl, figure 269, is a pyriform sac attached to the under 

 surface of the liver, and supported also by the peritoneum. The larger end, 

 or fundus, projects beyond the front margin of the liver, while the smaller 

 end contracts into the cystic duct. It is a muscular walled reservoir covered 

 with a serous epithelium and lined by mucous membrane. The function 

 of the gall-bladder is to retain the bile during the interval of digestion. 



The Bile. The bile is a somewhat viscid fluid, of a yellow, reddish- 

 yellow, or green color, a strongly bitter taste, and, when fresh, with a scarcely 

 perceptible odor; it has a neutral or slightly alkaline reaction, and its specific 

 gravity is about 1.020. Its color and consistency vary much, quite inde- 

 pendent of disease; but, as a rule, bile becomes gradually more deeply colored 

 and thicker as it advances along its ducts, or when it remains long in the gall- 

 bladder where it becomes more viscid and ropy, darker, and more bitter. 

 This is on account of its greater degree of concentration, from resorption of 

 its water, and also from being mixed with mucus, lipoids, and phosphatid 

 proteins secreted by the lining membrane of the gall-bladder. 



CHEMICAL COMPOSITION OF HUMAN BILE. (FRERICHS.) 



Water 859.2 



Solids Bile salts 91.5 



Fat 9.2 



Cholesterol 2.6 



Proteins and coloring matters 29.8 



Salts 7.7 



140. 8 



1000.0 



Bile salts can be obtained as colorless, exceedingly deliquescent crystals, 

 soluble in water, alcohol, and alkaline solutions, giving to the watery solution 

 the taste and general characters of bile. They consist of sodium salts of gly- 

 cocholic and taurocholic acids; the formula of the former being C 26 H 42 NaNO 6 , 

 and of the latter C 26 H 44 NaNSO 7 . 



The bile acids are easily decomposed by the action of dilute acids or alkalies 

 thus: 



C 26 H 43 N0 6 + H 2 = C 24 H 40 6 + CH 2 .NH 2 .COOH. 

 Glycocholic Acid Cholic Acid Glycocoll 



C 26 H 46 NSO 7 + H 2 O = C 24 H 40 O 5 + CH 2 .NH 2 .CH 2 SO 3 H. 

 Taurocholic Acid Cholic Acid Taurine 



Glycocoll is amido-acetic acid, i.e., acetic acid, CH 3 COOH with one of the atoms of H 

 replaced by the radical amidogen CH 2 .NH 2 .COOH. Taurine likewise is amino-ethyl- 

 sulphonic acid. Accordingly, it has the formula CH 2 NH 2 CH 2 SO 3 H. The proportion of 

 these two salts in the bile of different animals varies, e.g., in the ox bile the glycocholate is in 

 great excess, whereas the bile of the dog, cat, bear, and other carnivora contains taurocho- 

 late alone. In human bile the glycocholate is in excess (4.8 to 1.5). 



The yellow coloring matter of the bile of man and the carnivora is termed 



