2 4 S HEMOGLOBIN. 
globin. The ingenious conception of Hufner will be rendered evident by the 
three following equations : — 
(1) 6X0 + 2(Hb-0 2 ) = 4X0, + 2(Hb-N0). 
(2) 4(X0 o ) + 2(H„0) = 2(N0 o H) + 2(X0 3 H). 
(3) 2(X0lH) + CH 4 X,0 = 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 methemo- 
globin. 
Whether the more firmly combined oxygen of methemoglobin were capable 
of oxidising nitric oxide or not, the oxygen of oxyhemoglobin would certainly 
be able to do so, and Hufner proceeded to compare the amount of X liberated 
in the above reaction by solutions of exactly corresponding concentration of 
oxyhemoglobin and of alkaline methemoglobin. The results left no room for 
doubt, and led to the conclusion that when oxyhemoglobin is converted into 
methemoglobin, 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 X0. 2 . 
The compounds of methsemoglobin with nitrites. — I showed, as 
has already been stated, that when a solution of pure oxyhemoglobin 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 methaemoglobin, 
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 hemoglobin 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 Avater 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 oxyhaemoglobin with nitrites 
existing. 
The compounds of methaemoglobin 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 cj'anides, 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 methoemo- 
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 HCX of extreme dilution to a 1 or 2 per cent, solution 
of methaemoglobin, these assume a beautiful bright red colour, whilst the 
absorption band or bands of methaemoglobin have disappeared, and are 
replaced by a single broad absorption-band between D and E, occupying about 
the position of the band of reduced haemoglobin. 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 
methcTmoglobin to be a compound of the two bodies, and he ascribes to it the 
name "cyanogenmethaemoglobin," and represents it for brevity by the symbol 
CXHMetHb. 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 HCX on methaemoglobin 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 Nacbweis der Blausaure," Stuttgart, 1S91. 
