648 LOUIS BAUMAN 



salts exert a distinct cholagogue effect, and as they are continually absorbed 

 from the intestine a physiological stimulation of bile secretion is main- 

 tained. During its sojourn in the gall bladder the water content of the 

 bile is decreased and mucin and calcium salts are added. The urea content 

 of the bile is similar to that of the blood. 



Bile Salts. The sodium salts of taurocholic and glycocholic acids 

 (the latter predominates in human bile) and of desoxycholic acid are 

 present in the bile. Ordinary cholic acid has 3 hydroxy groups (C 23 H 36 - 

 (OH) :{ COOH), while desoxycholic acid, as its name implies, has 2 (C 23 - 

 H 37 (OH) 2 COOH). The derivation of cholic and desoxycholic acids from 

 cholesterol has been definitely established by Windaus. The salts of 

 the bile acids are soluble in alcohol but insoluble in ether, and these 

 properties are utilized in the process of their isolation. They are further 

 characterized by their reaction with furfurol in the presence of concen- 

 trated sulphuric acid, the so-called Pettenkofer test. At present there is 

 no evidence that bile acids are formed elsewhere than in the liver. The 

 bile salts, especially those of desoxycholic acid, form soluble addition 

 compounds with the fatty acids from stearic to formic. Cholesterol also 

 becomes soluble in the presence of bile salts (Wieland). The importance 

 of this property in the digestion and absorption of fats and cholesterol is 

 apparent. It is possible that the bile salts keep the cholesterol in bile in 

 solution. Wieland has shown that desoxycholic acid is toxic for heart and 

 striped muscle. Dog bile contains taurocholic acid almost exclusively, 

 and of this about 2 or 3 grams are excreted each day. When taurocholic 

 acid is administered to a dog, it is excreted fairly rapidly in the bile and 

 stimulates its flow (Foster, Hooper and Whipple). Eck fistula dogs 

 excrete only about one-half the normal amount of bile acids. The adminis- 

 tration of cystin to a bile fistula dog is followed by an increased secretion 

 of taurocholic acid. 



S-CH 2 -CHNH 2 COOH ^NHL>-CH 2 -CH 2 -SO 3 H 



S-CH 2 -CHNH 2 COOH (Taurm) 



(Cystin) 



Feeding cholesterol or red cells is without effect. 



Bile Pigments. The chief pigment of human bile is bilirubin. Bill 

 rubin is a pyrole derivative closely allied to hemoglobin. It dis- 

 solves readily in warm chloroform and dimethylanilin, but is spar- 

 ingly soluble in most of the other organic solvents. It can be obtained 

 in crystalline form- and is readily oxidized to biliverdin even by the oxygen 

 of the air. It is acidic in nature and forms an insoluble salt with calcium. 

 The average daily excretion of bilirubin by dogs is about 140 milligrams. 

 According to Paton and Balfour human bile contains from 0.4 to 1.3 

 grams of bilirubin per liter. 



