744 PHYSIOLOGY OF DIGESTION AND SECRETION. 



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 mucin. 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 Hammarstent 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 



......................... - 0220 ' 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- 

 bivora is a bright green from the biliverdin. The color of human bile 

 seems to vary : according to some authorities, it is yellow or golden 

 yellow, and this seems especially true of the bile as found in the gall- 

 bladder of the cadaver; according to others, it is of a dark-olive color 

 with the greenish tint predominating. Its reaction is feebly alkaline, 

 and its specific gravity varies in human bile from 1.050 or 1.040 to 

 1.010. Human bile does not give a distinctive absorption spectrum, 

 but the bile of some herbivora, after exposure to the air at least, gives 

 a characteristic spectrum. 



*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. 



f Reported in " Centralblatt f. Physiologic," 1894, No. 8. 



