THE PIGMENTS OF THE URINE. 313 



freshly voided, however, they commonly present a normal color. 

 The pigment or pigments which are thus formed belong to the class 

 of melanins, and are identical with those which can be obtained 

 from the pigmented growths. They are probably eliminated in 

 combination with some other substance which is as yet unknown, as 

 colorless melanogens and from which the free pigments are obtained 

 on oxidation. They are unquestionably derived from the common 

 pigments of the blood, but are individually little known. 



To prove that the change in the color of the urine is referable to 

 melanins, a fresh specimen should be procured, and treated with 

 bromine-water. If the chromogens in question are present, the 

 resulting precipitate, which is yellow at first, turns black on standing. 

 On the addition of a few drops of a strong solution of ferric 

 chloride a similar reaction is obtained. 



To isolate the pigments from the urine, the fluid is first precipi- 

 tated with an alkaline solution of barium chloride. From the 

 resulting precipitate the pigments are extracted with a concentrated 

 solution of sodium carbonate, and are then precipitated by adding 

 an excess of sulphuric acid. By redissolution in a dilute solution 

 of sodium hydrate and reprecipitation with acetic acid they can be 

 obtained in comparatively pure form. But it will be noted that a 

 certain fraction remains in the acetic acid solution, which indicates 

 the existence of at least two different pigments. The soluble 

 form has been termed phymatorhusin, and, according to Nencki 

 and Sieber, contains no iron, while Morner claims that this is 

 present. Elementary analysis of this pigment has given the fol- 

 lowing results (Morner) : 



From growth. From urine. 



Carbon 55.32 to 56.13 per cent. 55.76 per cent. 



Hydrogen 5.65 to 6.33 " 5.95 " " 



Nitrogen 12.30 " " 12.27 " " 



Sulphur 7.97 " " 9.01 " " 



Iron 0.063 to 0.081 " " 0.20 " " 



From melanotic growths in horses a hippomelanin has been 

 obtained, which, in contradistinction to the first, is soluble in solu- 

 tions of the alkalies with difficulty. 



The Bile-pigments. Bile-pigments are never found in the 

 urine under normal conditions. As a rule, freshly voided urine 

 contains only bilirubin. If a complicating cystitis, however, exists, 

 the common derivatives of bilirubin, viz., biliverdin, bilifuscin, 

 biliprasin, and bilihumin, may also be encountered. 



Bile-containing urines present a very characteristic color, which 

 may vary from a bright golden-yellow to a greenish brown, and on 

 microscopical examination it is common to find the morphological 

 elements stained an intense yellow. This color is further imparted 

 to the foam on shaking. But as urobilin when present in large 

 amounts may impart a similar color to the urine, it is always 



