392 



A TEXTBOOK OF PHYSIOLOGY 



I., obtained from gall-bladder of persons accidentally killed while in 

 good health; II., obtained from a fistula during life; 



IN 100 PAKTS OF BILE. 



1. 



Water 80 



Solids 14 



Organic salts . . .9 



Mucin and pigme.it . 3 



Cholesterol .... . 0-2 



Lecithin and fat 



Inorganic salts . . . 0-8 



II * 



97 

 3 



0-9 to 1-8 

 0-5 



0-06 to 0-16 

 0-5 to 1-0 0-02 to 0-09 

 0-7 to 0-8 



The Organic Salts. The organic salts are the sodium salts of the 

 bile acids. These acids are known as glycocholic (C 26 H 43 N0 6 ) and 

 taurocholic (C 26 H 45 NSO_). The former is more abundant in herbivora, 

 the latter in carnivora. The bile acids are formed in the liver, and 

 are compounds cf cholic or cholalic acid with the amino-acids 

 glycin and taurin respectively. Cholalic acid is probably related 

 to cholesterol; it contains two primary and one secondary alcoholic 

 groupings. It is probable, also, that there are several varieties of it, 

 and therefore several varieties of glycocholic and taurocholic acids. 

 Glycin is mon-amino- acetic acid, CKjNILjCOOH (see p. 40). Taurin is 

 amino-ethyl-sulphonic acid, CE^ NHg CHg S0 2 OH, and is derived 

 from cystin, COOH-CHNH 2 CH 2 S-SCH 2 CHNH 2 COOH. 



This is converted by rediictien into cystein, and this by oxidation 

 to cysteinic acid, COOH CHNH 2 -CH 2 Sd 2 OH, which, by the loss of 

 a molecule of C0 2 , yields taurin. 



The salts of the bile acids are dextro-rotatory, and crystallize in 

 fine needles or prisms. It is due to their presence that lecithin and 

 cholesterol are soluble in the bile. In the intestine, they are decom- 

 posed by bacterial action into their constituent parts, and mostly 

 reabsorbed, only a small amount of cholalic acid being found in the 

 fseces. The exact fate of the taurin is not known. 



Sodium glycocholate 



Glycocholic acid 



Glvcin 



(holding cholesterin in 

 solution) 



Cholalic acid 



Small a mount 'with 

 cholesterin in faeces 



Sodium taurocholate 



Taurocholic ac;d 



Taurin 



Reabsorbed 



The bile salts can be recognized by the fact that, when added to 



* The average quantity secreted in twenty-four hours varies from 500 to 1,000 c.o. ; 

 on an average about 750 c.c. 



