338 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



and bile salts. 581 According to West and Todd, 682 the average composition 

 and range in composition of human fistula bile, in parts per 1000, as re- 

 ported by various workers since 1900, are as follows: total lipids, 3.4 

 (2.9-4.2); neutral fat, 1.1 (0.4-3.0); fatty acids (including soaps), 1.1 

 (0.8-1.4); phosphatides, 0.6 (0.5-0.6); and cholesterol, 1.2 (0.8-1.7). 

 A similar compilation, by these authors, of the composition of human 

 bladder bile gives the following values: total lipids, 22.5 (19-26) ; neutral 

 fat, 3.7 (1.5-5.6); fatty acids (including soaps), 9.7 (9-10.9); phospha- 

 tides, 2.0 (1.8-2.2); and cholesterol, 6.3 (3.5-9.3). Friedman el aZ. 583 

 reported that the amount of cholesterol in rat bile was 12.7 milligram 

 per cent; the concentration was similar to that in dog bile. Heersehma 

 and Annegers 584 showed that cholecystectomy (removal of the gall blad- 

 der), which converts the normal intermittent flow of concentrated bile 

 into a continuous flow of dilute bile into the intestine, did not produce 

 any significant change in the daily excretion of fat in the feces. 



Although the bile serves as one pathway for the excretion of cholesterol, 

 Bloor 87 is of the opinion that it is a minor one. Gardner 585 stated that 

 the cholesterol eliminated in the bile is subsequently reabsorbed in the 

 small intestine; if such a reabsorption is quantitative, bile does not serve 

 any useful purpose in removing cholesterol from the organism. 



Under certain conditions, the bile is no longer able to hold all of its 

 cholesterol in solution, and the sterol precipitates from it. This phe- 

 nomenon occurs principally in the gall bladder, where bile undergoes con- 

 centration. Any biliary calculi which develop in the bladder may be 

 composed of almost pure cholesterol, although they frequently also con- 

 tain bile pigments, soaps, CaC0 3 , and small amounts of other constit- 

 uents, in addition to cholesterol. It has been mentioned earlier that the 

 term, "cholesterol," was coined to denote the source of this substance in 

 gallstones (solid bile). 



a. Factors Altering the Lipid Content of Bile. In the classic experiments 

 of McMaster, 586 it was found that not only was the total cholesterol con- 

 tent of the bile augmented in the dog as a result of the feeding of cholesterol- 

 rich foods, but also higher concentrations of the sterol obtained under 

 such conditions. Some increase in cholesterol output in the bile likewise 



581 G. H. Whipple, Physiol Revs., 2, 440-459 (1922). 



582 E. S. West and W. R. Todd, Textbook of Biochemistry, Macmillan, New York, 1951, 

 p. 502. 



583 M. Friedman, S. O. Bvers, and F. Michaelis, Am. J. Physiol, 162, 575-578 (1950). 



584 J. R. Heersehma and J. H. Annegers, Proc. Soe. Exptl. Biol. Med., fin, 140-141 (1948). 

 586 J. A. Gardner, Biochem. J., 18, 777-784 (1924). 



586 P. D. McMaster, ./. Exptl. Med., 40, 25-42 (1924) 



