HEMOGLOBIN 13 



ment with ether, bile salts and the serum of an animal of a 

 different species. 



The stroma, consists of nucleoprotein, lecithin and cho- 

 lesterin. Oxyhcemoglobin, the loose combination of haemo- 

 globin and oxygen, can be obtained in crystalhne form. 

 It has a molecular weight of about 16,600 and contains 

 •3 per cent, of iron. It is easily dissociated into haemo- 

 globin and oxygen. The oxygen can be replaced by carbon 

 monoxide, which forms a far more stable compound. The 

 absorption bands of haemoglobin and its derivatives are 

 seen in Fig. 1. Oxyhaemoglobin gives a narrow band at 

 A 579, and a broader band at X 544. Reduced haemoglobin 

 gives a broad band at X 555. Carboxyhaemoglobin, which 

 is brighter in colour than oxyhaemoglobin, resembles spectro- 

 scopically oxyhaemoglobin, but both bands are slightly 

 nearer the red end, and the second band is better defined. 



Methcemoglohin, isomeric with oxyhaemoglobin, is, how- 

 ever, a more stable compound. It occurs pathologically 

 wherever there is excessive breakdown of red blood cor- 

 puscles. Its importance lies in the fact that it can be 

 formed by treating haemoglobin with potassium ferri- 

 cyanide. Alt>hough the resulting product contains the 

 same amount of oxygen as oxyhaemoglobin, the original 

 oxygen of the oxyhaemoglobin is quantitatively liberated. 

 This is, therefore, a method for determining the amount of 

 oxygen in blood. 



It has been suggested that oxyhaemoglobin has the 

 formula — 



Hb(| 



while methaemoglobin has the formula — 



Hb( 



Haemoglobin is composed of haematin (C34H34N405Fe), 



