2JO SECRETION OF BILE. 



The mean composition of human hile is : 



Water, , . 82 to 90 per cent. 



Bile-salts, . . 6 to 11 ,, 



Fats and soaps, . . 2 ,, 



Cholesterin, . . 0*4 ,, 



Lecithin, . . . 0*5 per cent. 



Mucin and pigments, . 1 to 3 



Ash 0'61 



Further, unchanged fat probably'always passes into the bile, but it is again absorbed therefrom 

 (Virchow). The amount of S in dry dog's bile = 2*8 to 3*1 per cent., the N = 7 to 10 per cent. 

 (Spiro) ; the sulphur of the bile is not oxidised into sulphuric acid, but it appears as a sulphur- 

 compound in the urine (Ktinkel, v. Voit). 



178. SECRETION OF BILE. (1) 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. It is secreted continually ; but part is 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, 

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

 merely filtered through the blood-capillaries, as the pressure within the bile-ducts 

 may exceed that in the portal vein. 



(2) The quantity of bile was estimated by v. Wittich, from a biliary fistula, at 

 533 cubic centimetres in twenty-four hours (some bile passed into the intestine) ; 

 by Westphalen, at 453 to 566 grms. [by Murchison, at 40 oz.] ; by Joh. Ranke, on 

 a biliary-pulmonary fistula, at 652 cubic centimetres. The last observation gives 

 14 grms. (with 044 grms. solids) per kilo, of man in twenty-four hours. 



Analogous values for animals are 1 kilo, dog, 32 grm. (1*2 solids) ; 1 kilo, rabbit, 137 grm. 

 (2*5 solids) ; 1 kilo, guinea-pig, 176 grms. (2*5 solids). 



(3) The excretion of bile into the intestine shows two maxima during one period 

 of digestion; the first from 3 to 5 hours, and the second from 13 to 15 hours, 

 after food. The cause is due to simultaneous reflex excitement of the hepatic blood- 

 vessels, which become greatly dilated. 



(4) The influence of food is very marked. The largest amount is secreted 

 after a flesh diet, with some fat added ; less after vegetable food ; a very small 

 amount with a pure fat diet ; it stops during hunger. Draughts of water increase 

 the amount, with a corresponding relative diminution of the solid constituents. 

 [The biliary solids are increased by food, reaching their maximum about one hour 

 after feeding.] 



(5) The influence of blood-supply is variable : 



(a) Secretion is greatly favoured by a copious and rapid blood-supply. The blood-pressure 

 is not the prime factor, as ligature of the cava above the diaphragm, whereby the greatest 

 blood-pressure occurs in the liver, arrests the secretion. 



(b) Simultaneous ligature of the hepatic artery (diameter 5 mm.) and the portal vein 

 (diameter, 16 mm.) abolishes the secretion (Mhrig), These two vessels supply the raw 

 material for the secretion of bile. 



(c) If the hepatic artery be ligatured, the portal vein alone supports the secretion. Ligature 

 of the artery or one of its branches ultimately causes necrosis of the parts supplied by that 

 branch, and eventually of the entire liver, as this artery is the nutrient vessel of the liver. 



(d) If the branch of the portal vein to one lobe be ligatured, there is only a slight secretion in 

 that lobe, so that the bile must be formed from the arterial blood. Complete ligature of the portal 

 vein rapidly causes death ( 87). Neither ligature of the hepatic artery by itself, nor gradual 

 obliteration of the portal vein by itself, causes cessation of the secretion^ but it is diminished. 

 That sudden ligature of the portal vein causes cessation is due to the fact that, in addition to 

 diminution of the secretion, the enormous stagnation of blood in the rootlets of the portal vein 

 in the abdominal organs makes the liver very anremic, and thus prevents it from secreting. 



(e) If the blood of the hepatic artery is allowed to pass into the portal vein (which has been 

 ligatured on the peripheral side), secretion continues (Schiff). 



(/) Profuse loss of blood arrests the secretion of bile, before the muscular and nervous 

 apparatus become paralysed. A more copious supply of blood to other organs e.g., to the 



