5O2 THE LIVER. [CH. xxxm. 



is absorbed, not by the portal vein, but by the lacteals, has no 

 such effect. 



The chemical process by which the constituents of the bile 

 are formed is obscure. We, however, know that the biliary 

 pigment is produced by the decomposition of haemoglobin. Bili- 

 rubin is, in fact, identical with the iron-free derivative of hsemo- 

 globin called haematoidin, which is found in the form of crystals 

 in old blood-clots such as occur in the brain after cerebral 

 haemorrhage (see p. 429). 



An injection of haemoglobin into the portal vein or of substances 

 like water which liberate haemoglobin from the red blood corpuscles 

 produces an increase of bile pigment. If the spleen takes any 

 part in the elaboration of bile pigment, it does not proceed 

 so far as to liberate haemoglobin from the corpuscles. No free 

 haemoglobin is discoverable in the blood plasma in the splenic 

 vein. 



The amount of bile secreted is differently estimated by different 

 observers ; the amount secreted daily in man varies from 500 c.c. 

 to a litre (1,000 c.c.). 



The constituents of the bile are the bile salts proper 

 (taurocholate and glycocholate of soda), the bile pigments (bili- 

 rubin, biliverdin), a mucinoid substance, small quantities of 

 fats, soaps, cholesterin, lecithin, urea, and mineral salts, of 

 which sodium chloride and the phosphates of iron, calcium, and 

 magnesium are the most important. 



Bile, is a yellowish, reddish -brown, or green fluid, according to 

 the relative preponderance of its two chief pigments. It has a 

 musk-like odour, a bitter-sweet taste, and a neutral or faintly 

 alkaline reaction. 



The specific gravity of human bile from the gall-bladder is 

 1026 to 1032 ; that from a fistula, 1010 to ion. The greater 

 concentration of gall-bladder bile is partly but not wholly 

 explained by the addition to it from the walls of that cavity 

 of the mucinoid material it secretes. 



The amount of solids in bladder bile is from 9 to 14 per 

 cent., in fistula bile from 1-5 to 3 per cent. The following table 

 shows that this low percentage of solids is almost entirely 

 due to want of bile salts. This can be accounted for in the way 

 first suggested by Schiff that there is normally a bile circu- 

 lation going on in the body, a large quantity of the bile 

 salts that pass into the intestine being first split up, then 

 reabsorbed and again secreted. Such a circulation would 

 obviously be impossible in cases where all the bile is discharged 

 to the exterior. 



