152 



PHYSIOLOGICAL CHEMISTRY. 



the variation in constitution depending upon the nature of the 

 cholic acid which enters into the combination. The bile acids are 

 present in the bile as salts of one of the alkalis, generally sodium. 

 The sodium glycocholate and sodium taurocholate may be isolated 

 in crystalline form, either as balls or rosettes of fine needles or in 

 the form of prisms having ordinarily four or six sides (Fig. 40, 

 below). The salts of the bile acids are dextro-rotatory. Among 

 other properties these salts have the power of holding the choles- 

 terol and lecithin of the bile in solution. 



Hammarsten has demonstrated a third group of bile acids in 

 the bile of the shark. This same group very probably occurs in 

 certain other animals also. These acids are very rich in sulphur 

 and resemble ethereal sulphuric acids inasmuch as upon treatment 

 with boiling hydrochloric acid they yield sulphuric acid. 



FIG. 40. 



BILE SALTS. 



The bile pigments are important and interesting biliary consti- 

 tuents. The following have been isolated : bilirubin, biliverdin, bili- 

 juscin, biliprasin, bilihunrin, bilicyanin, choleprcisin and choletelin. 

 Of these, bilirubin and biliverdin are the most important and pre- 

 dominate in normal bile. The colors possessed by the various 

 varieties of normal bile are due almost entirely to these two pig- 

 ments, the biliverdin being the predominant pigment in greenish 

 bile and the bilirubin being the principal pigment in lighter colored 

 bile. The pigments, other than the two just mentioned, have been 

 found almost exclusively in biliary calculi or in altered bile ob- 

 tained at post-mortem examinations. 



