934 



PHYSIOLOGY 



haemoglobin in the absence of oxygen. For this purpose a test-tube 

 containing a solution of sodium or potassium hydrate is placed in a 

 bottle with two necks containing a solution of haemoglobin, care being 

 taken not to spill any of the alkaline solution. Hydrogen is then passed 

 through the larger bottle until the haemoglobin is entirely reduced and 

 all the air is replaced by hydrogen. The bottle is then inverted so as to 



BC D 



FIG. 359. Absorption spectra of haemoglobin and its derivatives. 



1. Oxy haemoglobin. 2. Reduced haemoglobin. 3. Methaemoglobin. 

 4. Alkaline methaemoglobin. 5. Acid haematin in ether 6. Alkaline 

 haematin in rectified spirit. 7. Reduced haematin. 8. Acid haematopor- 

 phyrin. 9. Alkaline haematoporphyrin. (From MACMUNN.) 



mix its contents with the caustic alkali, when haemochromogen is formed 

 and can be recognised by its characteristic colour and spectrum. The 

 haemochromogen in solution has a cherry-red colour, and when 

 sufficiently diluted shows two well-marked absorption bands identical 

 with those given by reduced alkaline hsematin (Fig. 359,7). Of the two 

 absorption bands which are situated between D and E, that nearest to 

 D has very sharply defined borders ; the position of the two absorption 

 bands may be given in terms of their wave-lengths as follows : X 567 to 

 547 and X 532 to 518. The band nearest D is given by hasmochromogen 



