CHEMISTRY OF HEMOGLOBIN 



355 



solution a dark red substance, Hematoporphyrin, or iron-free hematin 

 is deposited, the iron originally contained in the hematin molecule 

 being left in the solution in the form of Ferric Sulphate. Hemato- 

 porphyrin is identical with a substance known as Hematoidin which 

 is frequently found in the form of microscopical rhombic crystals in 

 old extravasations of blood or apoplectic clots. It is also identical 

 with Bilirubin, the red coloring-matter of the bile. 



When hemoglobin is decomposed by alkalies in the absence of oxygen, 

 we obtain Hemochromogen, or "reduced hematin." This substance 

 yields bright red solutions in alkaline media, acids very quickly change 

 it into hernatoporphyrin and a ferrous salt: 



Hematin. 



2H 2 O + 2HC1 



H 2 



Hematoporphyrin. 



By reduction of hematoporphyrin we obtain, among other products, 

 a substance known as Hemopyrrole, C 8 Hi 3 N, which is a methyl propyl 



pyrrole: 



HC - C - CH 2 .C 2 H 5 



HC 



C CH 3 



NH 



From its quantitative composition and the abundance of Methyl 

 Pyrrole derivatives among its decomposition-products, it appears 

 probable that hematin may be built up out of four methyl pyrrole 

 radicals united by iron and oxygen. The hydrochloride, or Hemin 

 may possibly be represented by the following structural formula: 



-CH=C(OH) C=C CH=CH C C CH 3 



HC CH 



\ 



O FeCl 



\/ 

 NH 



CH 3 C 



HC 



:: CH=C(OH) < 



^ CH 3 



\/ 

 NH 



CH 



/ 



HC 



CH 



NH 



The extensive investigations of Marchlewski, to whom we owe 

 much of our knowledge of these pigments, have resulted in establishing 

 the very close relationship which exists between hematin and Chloro- 

 phyll, the green pigment of plants. Thus among the products resulting 



