H^MOCHROMOGEN 



23 



A. Haemabln 

 C34H 32 N 4 O4 Pe H + protein < 



alkali 



Occyhaemoglobcn 



13 



C34H32N4 04[^ + protein 

 B. Reduced haemabln 



■^ Haemochromogen 



On the two schemes the bodies represented by the letters A, B, C, 

 etc. are identical, whatever names are attached to them. D on Anson 

 and Mirsky's scheme is, according to KeUin, non-existent in acid and 

 alkaline solutions. In neutral solutions, however, there is admittedly 

 a conjugated protein which corresponds to an oxidised form of 

 haemochromogen and which would occupy the position assigned to 

 hsematin by Anson and Mirsky. This body has a spectrum quite 

 different from anything which is obtained from the oxidation of 

 haemochromogen in alkaline solution. The substance has been 

 noticed by more than one observer. By v. Klaveren{5) it was called 

 " kathaemoglobin," by Keilin (4), who has appreciated its real structure, 

 it has been called "parahaematin." 



In what follows I shall adopt the nomenclature of Keilin and of 

 Hill and Holden(6), retaining haematin for the base C34H3oN404FeOH, 

 reduced haematin for the base C34H3oN404Fe, and haemochromogen for 

 the conjugated protein obtained by adding a nitrogenous substance 

 to the latter. Having grasped the essential point, namely, that haemo- 

 chromogen is made by the addition of globin to the base C34H3oN404Fe, 

 it is desirable to look into the reaction more particularly. The fact is 

 worth emphasis that the reaction is a balanced one. The equilibrium 

 between a haemochromogen and its constituents may be described 

 in general terms as follows : 



reduced haematin + nitrogenous compound ^^^ haemochromogen. 

 The most obvious example is 



reduced haematin + NH3 ^:^ NH3 haemochromogen. 

 If this description is correct it must be possible by a suitable altera- 

 tion in the relative concentrations of the reacting substances to make 

 the equilibrium go in either direction. An increase in the concentra- 

 tion of haemochromogen, on the addition of either reduced haematin 



