428 



THE BLOOD. 



[CH. XXVK 



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Fig. 360. Oxyhremoglobin crystals tetrahedral, 

 from blood of the guinea-pig. 



sation ; this probably explains their different crystalline form and 

 solubilities. Different observers have analysed haemoglobin. They 

 find carbon, 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 haemo- 

 globin, it is broken up 

 into two parts a brown 

 pigment called hcematin, 

 which contains all the 

 iron of the original sub- 

 stance, and a proteid 

 called glolin. 



Haematin is not crys- 

 tallisable ; it has the 

 formula CgiHggN^eOg 

 (Hoppe-Seyler), or 

 C32H3oN 4 Fe0 3 (Xencki 

 and Sieber) ; its consti- 

 tutional formula is, 

 however, not known- 

 Hsematin presents dif- 

 ferent spectroscopic ap- 

 pearances in .acid and 

 alkaline solutions (see 

 accompanying plate). 



Globin is a somewhat 

 curious proteid ; it is- 

 coagulable by heat, solu- 

 ble in dilute acids, and 

 precipitable from such 



Solutions by ammonia. 

 Jt closely resembles a 



substance previously 



separated from red corpuscles by Kossel, and termed by him 

 histone. (Schulz.) 



Hsemochromogen is sometimes called reduced hsematin ; it 

 may be formed by adding a reducing agent like ammonium 

 sulphide to an alkaline solution of hsematin. Its absorption 

 spectrum shown on the accompanying plate (No. 8), forms the 



Fig. 3 6i.-Hexagonal oxrh OS lobin crystals, from 

 blood of squirrel. (After Funke.) 



