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XII 



156. Bile is a mixture of the secretion of liver cells and 

 of mucin derived from the cells lining- the gall bladder and 

 duct. The bile obtained directly from the liver contains 

 about 2%, and that from the gall bladder contains about 12%, 

 of solids. The difference is due to concentration in the gall 

 bladder and ducts, where also mucinous substances are added. 

 The bile is normally a reddish brown or greenish viscid fluid 

 with a bitter taste and a neutral or slightly alkaline reaction. 

 After a proteid diet the secretion is increased, whereas with 

 fats and carbohydrates it is less marked. The secretion is 

 also decreased in starvation. 



The compounds which make up the larger part of the 

 solid matter of the bile are the sodium salts of glycocholic and 

 taurocholic acids. Besides these and the biliary mucin there 

 are present fats, soaps, lecithin, and cholesterin, also a number 

 of inorganic salts of the alkalies, alkaline earths, and iron. 

 The color of the bile is due to the biliary pigments, bilirubin, 

 biliverdin. The source of bilirubin is undoubtedly hematin. 

 On reduction it yields hydrobilirubin which is closely related 

 if not identical with stercobilin '(found in the intestines, giving 

 color to feces), and with urobilin of urine. On oxidation bilir- 

 ubin yields biliverdin. The amount of pigment in the bile is 

 usually only a few hundredths of a per cent., rarely 0.1%. As 

 to the origin of these bile constituents it may be said that the 

 bile acids are elaborated by the cells of the liver, not elsewhere 

 in the body. The bile pigments may possibly be formed in 

 other parts of the body than in the liver, but under normal 

 conditions the liver is the organ where they are formed. 

 Taurin and glycocoU result from the decomposition of proteids 

 in any part of the body. The bile contains no proteids nor 

 formed elements, but in some animals a small amount of dias- 

 tatic enzyme may be found. 



157. Note the peculiar odor of bile. Pcur a little from 

 one vessel to another and note the viscidity, due to the presence 

 of mucin and nucleo-proteid. 



158. Place some dilute bile (1 to 5) in a test tube and heat 

 to boiling. Immerse a strip of red litmus paper, then remove 



