METH.ZMOGLOBIN. 245 



is found to have become acid and to exhibit a spectrum in which, in 

 addition to the two bands of oxyhsemoglobin, one is seen in the red, 

 occupying much the position of the band of acid hematin. 



Hoppe-Seyler applied the name of inethsemoglobin 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 

 oxyh?emoglobin, 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 oxyhsemoglobin 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 oxyhsemoglobin 

 into methaemoglobin, though I committed the error of believing that the 

 changes described by me were due to the combination of nitrites with 

 oxyhsemoglobin, 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 oxyhgemoglobin is not 

 removed, but passes into a condition in which it is no longer removable 

 by boiling in vacuo or by the action of carbonic oxide. The action 

 of reducing agents reveals, however, as I showed, that the molecule 

 of loose oxygen of oxyhremoglobin 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 

 oxyhaemoglobin, which is only afterwards reduced. I pointed out that 

 the chocolate-coloured nitrite blood can be crystallised, the colouring 

 matter being isomorphous with haemoglobin 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 oxyhsemoglobin 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 methaBmo- 

 globin was, in every particular, exact, whilst the comparatively recent 

 statement, by Kobert, of the existence of combinations of hydrocyanic 

 acid and cyanides with methsemoglobin is an illustration of the class 

 of compounds of oxyhaemoglobin 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 oxy haemoglobin, 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 methsemoglobin, 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. 



