THE SECRETION OF BILE. 359 



with sulphuric acid (5 vol. to 1 vol. H 2 Moleschott), while they give a blue 

 as cellulose does with sulphuric acid and iodine. When dissolved in chloro- 

 form, 1 drop of concentrated sulphuric acid causes a deep red colour (H. Schiff). 



(5.) Amongst the other organic constituents of bile are: Lecithin 

 (p. 36), or its decomposition product, neurin (cholin), and glycero- 

 phosphoric acid (into which lecithin may be artificially transformed by 

 boiling with baryta); Pahnitin, Stearin,. Olein, as well as their soda 

 soaps ; Diastatic Ferment (Jacobson, v. Wittich) ; traces of Urea 

 (Picard) ; (in ox bile, acetic acid and propionic acid, united with 

 glycerine and metals, Dogiel). 



[The proportion of diastatic ferment is not greater than in the tissues of the 

 body generally (M. Hay).] 



(6.) Inorganic constituents of bile (0-6 to 1 p.c.): 



They are sodium chloride, potassium, chloride, calcic and magnesic phosphate, 

 and much iron, which in fresh bile gives the ordinary reactions for iron, so that 

 iron must occur in one of its oxidised compounds in bile (Kunkel); manganese and 

 silica. Freshly secreted bile contains in the dog more than 50 vol., and in the 

 rabbit 109 vol. per cent. C0 2 (Pfliiger, Boguljubow, Charles), partly united to 

 alkalies, partly absorbed, the latter, however, being almost completely absorbed 

 within the gall-bladder. 



Thejnean composition of human bile is : 



Lecithin, . . 0-5 p.c. 

 Mucin, . . 1-3 



Ash, 0-61 



Water, . 82-90 p.c. 



Bile Salts, 6-11 



Fats and Soaps, . 2 



Cholesterin, . . 0-4 



Farther, unchanged fat probably always passes into the bile, but is 

 again absorbed therefrom (Virchow). The amount of S in dry dog's 

 bile = 2-8-3-1 p.c., the N = 7-10 p.c. (Spiro); the sulphur of the bile is 

 not oxidised into sulphuric acid, but it appears as a sulphur-compound 

 in the urine (Kunkel, v. Voit). 



178. Secretion of Bile. 



The secretion of bile is not a mere filtration of substances already 

 existing in the blood of the liver, but it is a chemical production of the 

 characteristic biliary constituents, accompanied by oxidation, within the 

 hepatic cells, to which the blood of the gland only supplies the raw 

 material. The liver-cells themselves undergo histological changes 

 during the process of digestion (Heidenhain, Kayser). It is secreted 

 continually; it is partly stored up in the gall-bladder, and is poured 

 out copiously during digestion. 



The higher temperature of the blood of the hepatic vein, as well 

 as the large amount of C0 2 in the bile (Pfliiger), indicate that 

 oxidations occur within the liver. The water of the bile is not merely 



