ME TIL EMO GL OB IN. 245 
is found to have become acid and to exhibit a spectrum in which, in 
addition to the two hands of oxyhemoglobin, one is seen in the red, 
occupying much the position of the band of acid hematin. 
Hoppe-Seyler applied the name of methsemoglobin to the very 
indefinite and problematical body whose solutions possessed the above 
characters, and held it to be a product of the partial reduction of 
oxyhemoglobin, derived from it by the removal of a portion of the 
dissociable oxygen of that compound. 
I myself, soon after, investigated the changes brought about in the 
properties of oxyhemoglobin under the influence of nitrites, and in a 
memoir, 1 of which the experimental facts have, so far as they have yet 
been controlled, been confirmed in every particular, pointed out the 
remarkable phenomena, which attended the conversion of oxyhemoglobin 
into methsemoglobin, though I committed the error of believing that the 
changes described by me were due to the combination of nitrites with 
oxyhemoglobin, and not to an action which was afterwards shown to be 
possessed by a large number of both oxidising and reducing substances. 
I showed that blood which had been acted upon by nitrites, in addition 
to marked and definite changes in colour and spectrum, had almost 
entirely lost its power of absorbing oxygen from the atmosphere ; that, 
under the influence of nitrites, the oxygen of oxyhemoglobin is not 
removed, but passes into a condition in which it is no longer removable 
by boiling in tree no or by the action of carbonic oxide. The action 
of reducing agents reveals, however, as I showed, that the molecule 
of loose oxygen of oxyhemoglobin is still present in blood which 
has been acted upon by nitrites, for, in the absence of all traces 
of oxygen, reducing agents first of all and instantaneously liberate 
oxyhemoglobin, which is only afterwards reduced. I pointed out that 
the chocolate-coloured nitrite blood can be crystallised, the colouring 
matter being isomorphous with hemoglobin and its compounds, and 
that the crystals contain the nitrite which has brought about the 
change, though I showed that the composition of these molecular com- 
pounds of oxyhemoglobin is not a constant one. After innumerable 
contradictions, it has been proved, though without a word of acknow- 
ledgment, mainly by the researches of Hiifner and his pupils, that my 
account of the changes which characterise the formation of methemo- 
globin was, in every particular, exact, whilst the comparatively recent 
statement, by Robert, of the existence of combinations of hydrocyanic 
acid and cyanides with methsemoglobin is an illustration of the class 
of compounds of oxyhemoglobin which I was the first to discover and 
describe, and of which doubtless a large number will be obtained. 
Mode of preparation.- — A large number of inorganic and organic bodies, 
acting upon solutions of oxyhemoglobin, convert it into methsemoglobin. 
The chief of these are potassium ferricyanide — which, on account of the 
rapidity of its action, is to be preferred to all others — nitrites, chlorates, 
potassium permanganate, nitrobenzol, pyrogallol, pyrocatechin, acetanilid, etc. 
In order to study the spectroscopic characters of methaemoglohin, a 
solution of diluted blood is treated with a few drops of a strong solution 
of potassium ferricyanide, when the change in colour and spectrum is seen to 
occur almost instantly. To prepare the crystalline colouring matter, 2 or 
3 c.c. of a saturated solution of potassium ferricyanide or of a nitrite is 
1 A. Gamgee, "On the Action of Nitrites on Blood," Phil. Trans., London, 1868, vol. 
clviii. pp. 589-626. 
