360 PHYSIOLOGICAL CHEMISTRY. 



very bitter taste and an alkaline reaction; it varies widely in 

 composition, the total solids ranging from 9 to 17 per cent, 

 being always highest after a meal; its composition, moreover, is 

 highly complex ; the following is an average of five analyses of 

 bile from subjects with healthy liver : 



Water, 91.68 per cent. 



Mucus pigment, 1.29 



Taurocholate of sodium, 0.87 



Glycocholate of sodium, 3.03 



Fat, 0.73 



Soaps, 1.39 



Cholesterin, 035 



Lecithin, 053 



The true physiological action of bile is yet doubtful ; it is, 

 however, known that it acts on fats, forming with them an 

 emulsion which renders their passage through animal mem- 

 branes more easy; it also precipitates peptones, and it most 

 likely serves as a disinfectant, preventing putrefaction of the 

 organic matters during their passage through the intestines; 

 it finally acts as a natural purgative by irritation of the muscular 

 tissue of the intestines. 



Bile obtained after death is of a brownish-yellow color; 

 freed from mucus it will remain undecomposed for an almost 

 indefinite period. The mucus may be separated by the addition 

 of diluted alcohol and subsequent filtration. 



The quantity of bile discharged daily by a grown person may 

 be put at forty ounces, but a considerable quantity of this dis- 

 charged bile is reabsorbed in a changed form by the intestines ; 

 only a small amount of bile matters (in a decomposed state, 

 however) is discharged by the feces. 



Biliary pigments. Of these four are known, but it is probable 

 that more exist. Bilirubin, C 32 II 36 N 4 6 , is, when amorphous, an 

 orange-yellow powder; when crystalline, it forms red prisms. 

 It is sparingly soluble in water, alcohol, and ether, readily 

 soluble in hot chloroform and carbon disulphide. When treated 

 with a mixture of concentrated nitric acid and sulphuric acid 

 it turns first green, then blue, violet, red, and finally yellow. 

 This reaction, known as Gmelin's test, is used for the detection 

 of bile-pigments in urine and other fluids. 



