METHSEMOGLOBIN. 247 



the opinion that the colouring matter in methsemoglobin is in the same 

 state as in hsematin, the iron being, as he thought, in the condition of a 

 ferric compound, whilst in oxyhsemoglobin and in hsemochromogen he 

 believed it to exist in a ferrous state, though the grounds for these very 

 definite statements are certainly wanting. 



The researches of Hiifner on the oxygen of methsemoglobin. 



I had shown that the action of methsemoglobin, as produced by the action 

 of nitrites, could not be attended by a profound alteration in the constitution 

 of oxy haemoglobin, seeing that the addition of certain reagents at once caused 

 all the effects of the action to disappear, and revealed the continued existence 

 of oxidised haemoglobin. Nitrites (for these we should now read all agents 

 capable of transforming oxyhaBmoglobin into methsemoglobin) had, by my 

 experiments, been shown to resemble in no way those agents which thrust 

 oxygen out of the blood ; on the other hand, I had shown that the action of 



G HK L M N 



FIG. 36. The photographic spectrum of oxyhsemoglobin and methsemoglobin. 



nitrites resulted in ihe locking up of the oxygen of the blood, so as to render 

 it irremovable by carbonic oxide, or by a vacuum. But although I had dis- 

 covered that methaemoglobin, when treated with reducing agents, at once 

 liberates oxyhaBmoglobin, I had not been able to show that when the latter 

 substance is converted into the former the whole of its oxygen is locked up 

 without loss, and may be subsequently liberated. This was reserved for 

 Hiifner. 



When nitric oxide acts upon a solution of rnethaemoglobin, the brown 

 colour is changed to bright red, the spectrum of the red solution being 

 identical with that of NO-hsemoglobin. Eeflecting on this experiment, Hiifner 

 thought that perhaps NO possesses the power of becoming oxidised to N0 2 , 

 at the expense of the oxygen locked up in methsemoglobin (i.e. oxygen of 

 the original oxyhsemoglobin which had passed into a more stable combination). 



As such might be the case, it occurred to Hiifner to determine the volume 

 of N0 2 produced (for this would bear a definite relation to the abstracted 

 from methsemoglobin), by causing the nitrous acid (HN0 2 ), which would 

 be produced by the action of the water of the blood on N0 2 , to decompose 

 urea, the N liberated being a measure of the oxygen derived from niethaenio- 



