248 HAEMOGLOBIN. 



globin. The ingenious conception of Hiifner will be rendered evident by the 

 three following equations : 



(1) 6X0 + 2(Hb-0 9 ) = 4NO, + 2(Hb-NO). 



(2) 4(N0 2 ) + 2(H 2 6) = 2(N0 2 H) + 2(N0 3 H). 



(3) 2(N0 2 H) + CH 4 N 2 = 3(H 2 0) + 2C0 2 + 2(N 2 ). 



From these equations it results that each molecule of nitrogen liberated 

 will correspond to a molecule of oxygen which had become fixed in methsemo- 

 globin. 



Whether the more firmly combined oxygen of methsemoglobin were capable 

 of oxidising nitric oxide or not, the oxygen of oxyhsemoglobin would certainly 

 be able to do so, and Hiifner proceeded to oompare the amount of N liberated 

 in the above reaction by solutions of exactly corresponding concentration of 

 oxyhsemoglobin and of alkaline methsemoglobin. The results left no room for 

 doubt, and led to the conclusion that when oxyhsemoglobin is converted into 

 methsemoglobin, the whole of its oxygen passes into a state of more intimate 

 combination, so that it can no longer be removed either by CO nor by a 

 vacuum, but is yet available to oxidise such bodies as N0 2 . 



The compounds of metheemoglobin with nitrites. I showed, as 

 has already been stated, that when a solution of pure oxyhsemoglobin is 

 treated with a solution of a nitrite, so as to produce the change in colour 

 and spectrum which we now know to be characteristic of methsemoglobin, 

 the blood-colouring matter crystallised out of the solution is found to con- 

 tain the nitrite, though the proportion in which the latter combines with 

 the hsemoglobin is not constant. The discordance in results did not appear 

 to me surprising, and that " as in the case of other combinations of a molecular 

 kind, such as the union of salts with their water of crystallisation, of bases 

 with sugar, of albumin with metallic oxides, of iodine with the compound 

 ammonias, the amount of the simpler body added to the more complex should 

 vary within wide limits." I further speculated on the probability of a large 

 number of similar combinations to that of oxyhsemoglobin with nitrites 

 existing. 



The compounds of methsemoglobin with HCN and cyanides. 

 It has long been noticed that hypostatic marks on the bodies of men and 

 animals poisoned by prussic acid or metallic cyanides, as well as the mucous 

 membrane of the stomach, present a striking bright red colour. Kobert 1 

 surmised ..that this coloration might be due to combination of methsemo- 

 globin with HCN or metallic cyanides, a hypothesis of which he thinks 

 he has obtained confirmation from his experiments. Kobert found that on 

 adding solutions of HCN of extreme dilution to a 1 or 2 per cent, solution 

 of methsemoglobin, these assume a beautiful bright red colour, whilst the 

 absorption band or bands of methsemoglobin have disappeared, and are 

 replaced by a single broad absorption-band between D and E, occupying about 

 the position of the band of reduced hsemoglobin. This band cannot, however, 

 be made to disappear by the action of oxygen. 



According to Kobert, this band is not affected by the addition of ammonium 

 sulphide. He believes the body which is produced by the action of HCN on 

 methsemoglobin to be a compound of the two bodies, and he ascribes to it the 

 name " cyanogenmethsemoglobin," and represents it for brevity by the symbol 

 CNH'MetHb. He further lays claim to have discovered for the first time 

 similar compounds with nitrites (! !). But Kobert's view of the nature of the 

 action of HCN on methsemoglobin has not been universally accepted. The 

 absorption-spectrum which he has described as characteristic of his new 

 compound is identical with that described by Preyer as resulting from the 



1 " Ueber Cyanmethamoglobin und den Nachweis der Blausaure," Stuttgart, 1891. 



