206 PHYSIOLOGICAL CHEMISTRY 



certain metals, particularly calcium, to form combinations which are no 

 longer soluble in the solvents of the unaltered pigment. Upon long 

 standing in contact with the air, the reddish-yellow bilirubin is oxidized 

 with the formation of the green biliverdin. Bilirubin occurs in animal 

 fluids as soluble bilirubin-alkali. 



Solutions of bilirubin exhibit no absorption bands. If an ammonia- 

 cal solution of bilirubin-alkali in water is treated with a solution of zinc 

 chloride, however, it shows bands similar to those of bilicyanin (Absorp- 

 tion Spectra, Plate II), the two bands between C and D being rather 

 well defined. 



Biliverdin is particularly abundant in the bile of herbivora. It is 

 soluble in alcohol and glacial acetic acid and insoluble in water, chloro- 

 form, and ether. Biliverdin in formed from bilirubin upon oxidation. 

 It is an amorphous substance, and in this differs from bilirubin which 

 may be at least partly crystallized under proper conditions. Biliverdin 

 may be obtained in the form of a green powder. In common with 

 bilirubin, it may be converted into hydrobilirubin by nascent hydrogen. 



The neutral solution of bilicyanin or cholecyanin is bluish green or 

 steel blue and possesses a blue fluorescence, the alkaline solution is 

 green with no appreciable fluorescence, and the strongly acid solution is 

 violet blue. The alkaline solution exhibits three absorption bands, the 

 first a dark, well-defined band between C and D, somewhat nearer C; 

 the second a less sharply defined band extending across D and the third 

 a rather faint band between E and F, near E (Absorption Spectra, Plate 

 II). The strongly acid solution exhibits two absorption bands, both 

 lying between C and E and separated by a narrow space near D. A 

 third band, exceedingly faint, may ordinarily be seen between b and F. 



Bile pigments are converted into urobilinogen (urobilin) in the intes- 

 tine. This is absorbed, carried to the liver and reconverted into bile 

 pigment. In diseases of the liver the liver cell loses the capacity to 

 convert the urobilinogen and this is then excreted in the urine. The 

 presence of urobilinoger! in urine, therefore, may be considered as an 

 index of functional liver incapacity. 1 



Biliary calculi, otherwise designated as biliary concretions or gall 

 stones, are frequently formed in the gall-bladder. These deposits may 

 be divided into three classes, cholesterol calculi, pigment calculi, and 

 calculi made up almost entirely of inorganic material. This last class 

 of calculus is formed principally of the carbonate and phosphate of 

 calcium and is rarely found in man although quite common to cattle. 

 The pigment calculus is also found in cattle, but is more common to 

 man than the inorganic calculus. This pigment calculus ordinarily 



1 Rowntree, Hurwitz and Bloomfield: Johns Hopkins Hospital Bulletin, Nov., 1913. 



