564 MECHANISM OF BILE SECRETION. 



it. This was definitely proved by Wertheimer, 1 who injected into the 

 circulation of dogs the bile of the ox and sheep. The bile of these 

 animals contains a pigment, cholohsematin, which gives a characteristic 

 spectrum, and the appearance of this spectrum in the bile of the dog 

 showed that cholohsematin had been taken up and excreted. 



Cholesterin. Whether cholesterin is formed in the liver cells, or in 

 the cells lining the bile passages, or in both, is not definitely known. 

 In the two cases of fistula of the gall bladder already referred to, the 

 presence or absence of cholesterin is not noted. 2 



That the cholesterin is formed somewhere within the liver, and not 

 merely excreted by it, is shown by an experiment by Jankau, performed 

 in Naunyn's laboratory. 3 He injected cholesterin into dogs, and also 

 gave it in their food, and ascertained ^hat it had been absorbed ; but he 

 failed to find any increase of cholesterin in the liver tissue, or in the 

 bile. The analyses of the liver and bile made by Kausch 4 in the same 

 laboratory show no relationship between the amount of cholesterin in 

 the gland, and in its secretion. Thomas, 3 who also worked in Naunyn's 

 laboratory, found that there is no relationship between the amount of 

 cholesterin excreted and the kind of food taken. When the dog under 

 observation suffered from catarrh of the biliary passages, there was a 

 marked increase in the cholesterin of the bile. 



From these experiments, and from the fact that cholesterin is always 

 found where cells are disintegrating, Naunyn strongly supports the view 

 that cholesterin is produced, not in the liver cells, but from the cells of 

 the passages, and that it is a product of the disintegration of their 

 protoplasm. 



Lecithin and other compounds of the fatty acids. The occur- 

 rence of these bodies in the secretion from the gall bladder has not 

 been observed. On the other hand, lecithin and fat are constant and 

 abundant constituents of liver cells. Liver tissue contains about 2 -3 5 

 per cent, of lecithin, and about 3 or 4 per cent, of fat. 5 Thomas found 6 

 that, while cholesterin was unaltered in amount by the administration 

 of various diets, the amount of fat in the bile depended largely upon 

 the amount of fat taken in the food ; and since the fats of the food are 

 frequently stored in the liver cells, it is probable that the fatty acid 

 compounds in the bile are derived from this source. 



INFLUENCE OF VARIOUS FACTORS UPON THE SECRETION. 



The investigation of the influence of varying conditions upon bile 

 secretion is a matter of extreme difficulty, for the bile may accumulate 

 in the gall bladder and passages to be expelled from the liver some time 

 after secretion. 



The flow of bile is governed by 



1. The rate of secretion. 



2. The activity of the muscular walls of the passages. 



3. The pressure upon the liver of adjacent organs. 



1 Arch, de physiol. norm, etpatli., Paris, 1891, p. 724. 



2 In the colourless fluid from a case of hydrops cystidis fellese, I found a considerable 

 quantity of cholesterin. 



3 ''Cholelithiasis," translated by A. E. Garrod, New Syd. Sac., 1896. 



4 Diss., Strassburg, 1891. 



5 Noel Paton, Journ. Physiol., Cambridge and London, 1896, vol. xix. p. 213. 



6 Loc. cit. 



