THE BLOOD. 22Q 



red, the acid solutions incline to deep violet or purple. The 

 acid and alkali spectra are very different and characteristic. 



The relation of the blood coloring matter to the bile pig- 

 ments is illustrated by these formulas : 



hematin 



hematoporphyrin 

 bilirubin 

 biliverdin 



Hematolin is the name given to an iron free compound 

 obtained by decomposing hematin in absence of air. 



Hemochromogen. This is obtained by reducing a hema- 

 tin solution with ammonium sulphide or with zinc dust and 

 alkali. It forms a dark red powder insoluble in water but 

 soluble in alkalies. The solution exposed to the air absorbs 

 oxygen and appears to regenerate hematin. 



Hematoidin is a red-colored pigment which has been 

 found in old blood extravasations. It seems to be identical 

 with bilirubin. 



THE OTHER PROTEINS OF THE BLOOD. 



In addition to fibrin and hemoglobin blood contains serum 

 albumin and serum globulin, which have been described al- 

 ready in a previous chapter. The combined substances make 

 up about 7 per cent. They may be approximately separated 

 by precipitating the globulin from blood serum by addition of 

 a large volume of water and also by salt precipitation, which 

 may be illustrated in this way: 



Ex. Prepare blood serum as free as possible from corpuscles as already 

 shown and mix about 100 cc. with an equal volume of cold saturated am- 

 monium sulphate solution. A separation of the globulin follows. Filter; 

 the nitrate contains practically all the serum albumin which may be coagu- 

 lated by boiling. The albumin may be purified by long dialysis. To rec- 

 ognize the globulin in the precipitate, first wash the latter with more half- 

 saturated ammonium sulphate and then dissolve in slight excess of water. 

 It may be necessary to add a little common salt to assist in the solution. 

 On heating a portion of this solution coagulation follows. On diluting 

 some of it very largely with water precipitation of the globulin takes place 

 From the first water solution most of the salts may be separated by long 

 continued dialysis. 



