938 PHYSIOLOGY 



to Ham and Balean, when oxyhaemoglobin is converted by means of 

 acids into acid haematin, exactly half of the oxygen of the oxy haemo- 

 globin is given off, so that haematin would only contain one-half of the 

 oxygen of the oxyhaemoglobin. There is a marked difference between 

 the stability of haematin and haemochromogen. In the oxidised form 

 of hsematin the iron is firmly bound and can only be split off by using 

 strong sulphuric acid, concentrated hydrochloric acid being insufficient 

 for the purpose. 



Since pure haemochromogen is readily converted quantitatively 

 into haematoporphyrin, it seems to consist of a simple compound of 

 haematoporphyrin and iron in the ferrous condition. It has been shown 

 by Laidlaw that the change in the reverse direction, i.e. the combina- 

 ton of iron with haematoporphyrin to form haemochromogen, may be 

 effected with equal ease. One gramme haematoporphyrin prepared by 

 Nencki's method is dissolved in dilute ammonia and warmed in a flask on 

 the water-bath. Some Stokes's fluid, prepared from about 2 grm. ferrous 

 sulphate, and a few drops of a 50 per cent, hydrazine hydrate solution 

 are added. At the end of one or two hours the solution is seen to be of a 

 bright red colour when examined in thin layers, and on dilution shows 

 the typical absorption spectrum of haemochromogen, which changes 

 to that of alkaline haematin on shaking with air. Strong potash is 

 added, and the ammonia is boiled off in an evaporating dish with 

 free exposure to the air. The hydrazine is decomposed, and a solution 

 of haematin remains, and can be precipitated by acidification with 

 hydrochloric acid. The pigment obtained in this way agrees in every 

 respect with that prepared from oxyhaemoglobin. Analysis of the 

 product gave 9-58 per cent, of iron, which agrees with Nencki's formula 

 for haematin, C 3 2H 30 N 4 3 Fe. The ease with which this combination 

 is effected suggests that haematin consists of two haematoporphyrin 

 groups united by means of iron. 



A pigment occurring in the wing feathers of certain birds, called turacin, 

 was shown by Church to contain copper, and to yield, on treatment with strong 

 sulphuric acid, a substance indistinguishable from hsematoporphyrin. Laidlaw 

 has succeeded in synthetising this pigment by treating ordinary hsemato- 

 porphyrin obtained from blood with ammoniacal copper solution, showing that 

 it is a compound corresponding to hsematin, in which the place of iron is taken 

 by copper. 



It was stated some years ago by Menzies that a solution of impure 

 haemochromogen, prepared by the action of ammonium sulphide or 

 alkaline haematin obtained in the ordinary way from blood, on standing 

 for some days was reconverted into reduced haemoglobin. Ham and 

 Balean have confirmed this observation, and have shown in addition 

 that haemochromogen, prepared by the action of ammonium sulphide on 

 an alkaline solution of pure haemin, though perfectly stable by itself, 



