160 THE DIGESTIVE FLUIDS. 



then washed free from acid with water, and subsequently with abso- 

 lute alcohol, to remove the water and any biliverdin that may be 

 present. The pigment remains, and is now dissolved with boiling 

 chloroform. From this solution the chloroform is distilled off, the 

 residue extracted with absolute alcohol, so as to remove any bili- 

 fuscin, and the remaining bilirubin dissolved in a small amount of 

 chloroform and precipitated with alcohol. This procedure is 

 repeated until the substance has been obtained in pure form ; it 

 is then allowed to crystallize out from its chloroform solution on 

 cooling. 



Biliverdin. Biliverdin is found in the bladder-bile of many ani- 

 mals together with bilirubin, and is especially abundant in certain 

 herbivora, where the bile frequently presents a bright grass-green 

 color. It is said to occur also in the placenta of the bitch, in the 

 shells of certain mollusks, and in birds' eggs. Its relation to bili- 

 rubin has already been considered. In the bile it is present princi- 

 pally in the form of its sodium salt, and, like bilirubin, the free 

 pigment possesses acid properties ; this is termed biliverdinic acid, 

 but should not be confounded with the acid of the same name 

 which Ktister obtained from biliverdin on oxidation with sodium 

 chromate. In acid bile biliverdin is found as such. Unlike 

 bilirubin, the free pigment is readily soluble in normal as well as in 

 neutral and acid bile. It is insoluble in water, ether, and chloro- 

 form, but dissolves in alcohol, glacial acetic acid, and solutions of 

 the alkalies. From the latter it is precipitated by the salts of the 

 alkaline earths and the heavy metals, as also by acids. On treating 

 an alcoholic solution of biliverdin with ammoniacal chloride of zinc 

 solution the fluid exhibits a green fluorescence. The green color of 

 the pigment is changed to yellow if its solution in acid alcohol is 

 treated with zinc. If chlorine-water is added instead, a blue color 

 develops at the bottom of the liquid, and above it layers present- 

 ing a violet, a red and a yellow color will be observed. On adding 

 an excess of chlorine-water the solution is decolorized. 



Pure biliverdin, like bilirubin, gives no characteristic band of 

 absorption in alkaline solution. In acid solution, however, or in 

 pure alcoholic solution, an indistinct band is observed at D, and one 

 that is more pronounced near F. 



The substance is amorphous, or at least cannot be obtained in a 

 pronounced crystalline form. 



On reduction, biliverdin is supposedly transformed into bilirubin, 

 though this is denied by some observers. 



On oxidation with nitric acid biliverdin gives rise to the various 

 colors which have already been described, beginning with blue. It 

 gives Huppert's reaction directly. 



Isolation. To prepare biliverdin, it is most convenient to start 

 with a solution of bilirubin in the form of its sodium salt which lias 

 been exposed to the air until the original golden-yellow color has 

 changed to a brownish green. The biliverdin is then precipitated 



