390 HANDBOOK OF PHYSIOLOGY. 



The Bile. 



Properties. 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 1020. Its color and degree of consist- 

 ence vary much, quite independent 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, wherein, at the same time, 

 it becomes more viscid and ropy, darker, and more bitter, mainly from 

 its greater degree of concentration, on account of partial absorption of 

 its water, but also from being mixed with mucus. 



CHEMICAL COMPOSITION OP HUMAN BILE. (Frerichs.) 



Water 859.2 



Solids Bile salts 91.5 



Fat ....... 9.2 



Cholesterin 2.6 



Mucus and coloring matters . . 29. 8 



Salts 7.7 



140.8 



1000.0 



(a) Bile salts, sometimes termed Bilin, 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 glycocholic and taurocholic 

 acids. The formula of the former salt being C26H43~NaN06, and of the 

 latter C a 6 



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

 thus : 



C 2 H 43 NO 6 + H 2 O = C 2 H r ,NO 2 -f- C 24 H 40 O, 

 Glycocholic Acid. Glycin. Cholic Acid. 



and C 26 H 4 5NO 7 S -f H 2 O = C 2 H 7 NO 3 S -f C 24 H 40 O 5 

 Taurocholic Acid. Taurin. Cholic Acid. 



Glycin, or glycocin, is amido-acetic acid, i.e., acetic acid C 2 H 4 O 2 , with one 

 of the atoms of H replaced by the radical amidogen NH 2 ,C 2 H 3 (NH 2 )O 2 , 

 C 2 H 6 NO 2 . Taurin likewise is amido-isethionic acid. Isethionic acid is sul- 

 phurous acid H 2 SO 3 , in which an atom of H is replaced by the monotomic 

 radicle oxy-ethylene, C 2 H 4 OH, viz., H(C 2 H 4 OH)SO 3 , and in amido-isethionic 

 acid, the OH hydroxyl in this radicle is replaced by amidogen NH 2 , thus 

 H(C 2 H 4 NH 2 )SO 3 = C 2 H 7 NSO 3 . The proportion of these two salts in the bile of 

 different, animals varies, e.g. , in 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). 



Preparation of Bile Salts. Bile salts may be prepared in the following 

 manner : mix bile which has been evaporated to a quarter of its bulk with 



