72 PHYSIOLOGY OF ALIMENTATION. 



obtained at an ordinary post-mortem is yellowish brown, 

 brown, or green. The reaction of the bile is ordinarily 

 stated to be alkaline. It is probable, however, that it is 

 neutral. 



The most important constituents of the bile besides water 

 are the bile acids in combination with the alkali metals, and 

 the bile pigments. Among the other important constituents 

 are the inorganic salts which are universally present in the 

 body and fats, lecithin, cholesterin, urea, and soaps. 



The bile acids are several in number and are usually divided 

 into the glycocholic and taurocholic groups, each of which has 

 several members. The bile pigments are also several in num- 

 ber. The reddish-yellow bilirubin and the green bihverdin 

 are always present in bile under physiological conditions. 

 Hydrobilirubin perhaps also belongs to this group. Under 

 pathological conditions, as in gall-stones, a number of other 

 pigments besides those already mentioned may be found, 

 of which choletelin, bilifuscin, biliprosin, bilihumin, and 

 bilicyanin are the most important. Bilirubin and hydro- 

 bilirubin are of great physiological interest because of the 

 identity or at least close chemical relation of the former to 

 a derivative of haemoglobin, hsematoidin, and of the latter to 

 urobilin, one of the urinary pigments. 



The inorganic constituents of the bile comprise the chlo- 

 rides, phosphates, and sulphates of sodium, potassium, cal- 

 cium, magnesium, iron, and copper. Urea is found only in 

 traces. The following three analyses of human bile by 

 HAMMARSTEN; 1 which probably are as trustworthy as an}' at 

 our disposal, will give an idea of the relative proportions in 

 which the various constituents exist in this secretion. The 

 figures indicate parts per 1000. 



Water 974.800 964.740 974.600 



Solids 25.200 35.260 25.400 



HAMMARSTEN : Text-book of Physiological Chemistry. Translated 

 by MAN DEL, New York, 1904, p. 276. 



