loo HUMAN PHYSIOLOGY 



solids. The amount secreted per diem in the adult is about 

 i litre. 



Characteristic constituents of bile : 



(a) Sodium glycocholate and sodium taurocholate (about 

 one-third of all the solids of bile). In man the sodium 

 glycocholate predominates, in the dog, sodium taurocholate. 



To isolate the salts of the bile acids, proceed as follows: 

 Mix bile with animal charcoal, evaporate, extract the 

 residue with alcohol, add excess of ether; this precipitates 

 the salts of bile acids in delicate needle crystals (crystallized 

 bile). Concerning the characteristics of the bile acids see 

 page 49. 



(b) Bile pigments, bilirubin, biliverdin, and sometimes 

 also hydro-bilirubin ; see page 50. 



Besides these, bile contains mucin, cholesterin, lecithin, 

 fat and fatty acids, salts (chiefly sodium carbonate and phos- 

 phate), and a little iron. 



In the gall-bladder the solid constituents of the bile may be 

 precipitated as gallstones. These may be composed of a com- 

 pound of calcium with bilirubin or of cholesterin. 



2. Chemistry of the liver. The liver is the largest gland 

 in our body. It weighs about 1 . 5 kg and contains about 

 30$ solids, chiefly proteids (20$), some fats, extractives, and 

 a varying amount of carbohydrate in the form of glycogen 

 and grape-sugar. Its ash forms about i# of its weight and 

 is characterized by its high per cent of iron. 



The iron in the liver is partly in inorganic, partly in organic 

 combination. The iron held in organic union is found in two 

 nucleo-proteids, hepatin and ferratin. In the hepatin the iron is 

 held very closely, but ferratin has more the character of an iron 

 albuminate since its iron can be split off by hydrochloric acid. 



The iron of the liver, like the bile pigments, is derived from the 

 haemoglobin of the red blood corpuscles which are destroyed in 

 the liver. The iron is excreted chiefly by the walls of the intes- 

 tine, and in smaller quantities by the bile and urine. 



3 . Structure of the liver. The gland-cells of the liver are 

 irregular polygonal cells having granular protoplasm and 

 one or more nuclei. The protoplasm contains pigment 



