PHYSIOLOGY OF THE LIVER AND SPLEEN. 813 



Bile. From a physiological standpoint, bile is partly an excre- 

 tion carrying off certain waste products, and partly a digestive secre- 

 tion playing an important role in the absorption of fats, and possibly 

 in other ways. Bile is a continuous secretion, but in animals possess- 

 ing a gall-bladder its ejection into the duodenum is intermittent. 

 Bile is easily obtained from living animals by establishing a fistula 

 of the bile-duct or, as seems preferable, of the gall-bladder. The 

 latter operation has been performed a number of times on human 

 beings. In some cases the entire supply of bile has been diverted in 

 this way to the exterior, and it is an interesting physiological fact 

 that such patients may continue to enjoy fair health, showing that, 

 whatever part the bile takes normally in digestion and absorption, 

 its passage into the intestine is not absolutely necessary to the nu- 

 trition of the body. The quantity of bile secreted during the day 

 has been estimated for human beings of average weight (43 to 73 

 kgms.) as varying between 500 and 800 c.c. This estimate is based 

 upon observations on cases of biliary fistula.* Chemical analyses 

 of the bile show that, in addition to the water and salts, it contains 

 bile pigments, bile acids, cholesterin, lecithin, neutral fats and soaps, 

 sometimes a trace of urea, and a mucilaginous nucleo-albumin for- 

 merly designated improperly as mucih. The last-mentioned sub- 

 stance is not formed in the liver cells, but is added to the bile by the 

 mucous membrane of the bile-ducts and gall-bladder. The quantity 

 of these substances present in the .bile varies in different animals 

 and under different conditions. As an illustration of their relative 

 importance in human bile and of the limits of variation, the two 

 following analyses by Hammarstenf may be quoted: 



i. . ii. 



Solids 2.520 2.840 



Water 97.480 97.160 



Mucin and pigment 0.529 0.910 



Bile salts 0.931 0.814 



Taurocholate 0.3034 0.053 



Glycocholate 0.6276 0.761 



Fatty acids from soap 0.1230 0.024 



Cholesterin 0.0630 0.096 



Fat 1 * 1 " 11 } 0.0220 0.1286 



Soluble salts 0.8070 0.8051 



Insoluble salts 0.0250 0.0411 



The color of bile varies in different animals according to the pre- 

 ponderance of one or the other of the main bile pigments, bilirubin 

 and biliverdin. The bile of carnivorous animals has usually a 

 golden color, owing to the presence of bilirubin, while that of the her- 



*Copeman and Winston, "Journal of Physiology," 10, 213, 1889; Rob- 

 son, "Proceedings of the Royal Society," London, 47, 499, 1890; Pfaff and 

 Balch, "Journal of Experimental Medicine," 2, 49, 1897. 



t Reported in "Centralblatt f. Physiologic," 1894, No. 8. For other 

 analyses consult Rosenbloom, "Journal of Biological Chemistry," 14, 241, 1913. 



