430 



THE BLOOD 



[CH. XXVI. 



which consists in using Canada balsam instead of water in the fore- 

 going experiment. 



3. On a larger scale, crystals may be obtained by mixing the 

 blood with one-sixteenth of its volume of ether ; the corpuscles dis- 

 solve, and the blood assumes a laky appearance. After a period vary- 

 ing from a few minutes to days, abundant crystals are deposited. 



In nearly all animals the crystals are rhombic prisms (fig. 362) ; 

 but in the guinea-pig they are rhombic tetrahedra, or four-sided 

 pyramids (fig. 363); in the squirrel and hamster, hexagonal plates 

 (fig. 364). 



The crystals contain a varying amount of water of crystallisation ; 

 this probably explains their different crystalline form and solubilities! 

 Several observers have analysed haemoglobin. They find carbon, 



FIG. 363. Oxyhaemoglobin crystals tetrahedral, 

 from blood of the guinea-pig. 



FIG. 3(34. Hexagonal oxyha>moglobin crystals, 

 from blood of squirrel. (After Funke.) 



hydrogen, nitrogen, oxygen, sulphur and iron. The percentage of 

 iron is 0*4. The amounts of the other elements are variously given, 

 but roughly they are the same as in the proteids. On adding an 

 acid or alkali to haemoglobin, it is broken up into two parts a brown 

 pigment called hcematin, which contains all the iron of the original 

 substance, and a proteid called globin. 



Haematin is not crystallisable ; it has the formula 034113^^605 

 (Hoppe-Seyler), or C 32 H3 N 4 Fe0 3 (Nencki and Sieber) ; its consti- 

 tutional formula is, however, not known. Hsematin presents different 

 spectroscopic appearances in acid and alkaline solutions (see accom- 

 panying plate). On decomposition it yields pyrrol derivatives. 



Globin is a somewhat curious proteid ; it is coagulable by heat, 

 soluble in dilute acids, and precipitable from such solutions by 

 ammonia. It closely resembles a substance previously separated from 

 red corpuscles by Kossel, and termed by him historic. (Schulz.) 



