230 METHJEMOGLOBIN. 



to its purification a copious crop of reddish-brown crystalline needles 

 was obtained. These were found on examination to be crystals of 

 methsemoglobin. 1 They are most easily obtained if the oxy-haemoglobin 

 is first converted into methsemoglobin by the action of potassium 

 ferricyanide (one or two minute crystals of the salt to half a litre 

 of warm concentrated solution of oxy-hsemoglobin) ; the mixture is 

 then shaken until it has a dark brown colour and is cooled to 

 after the addition of one quarter of its bulk of alcohol also cooled 

 to 0. They have also been obtained from the blood of the dog 2 , 

 horse 3 and other animals 4 , and resemble in crystalline form the 

 crystals of oxy-hsemoglobin from the same sources. These crystals 

 are doubly refracting, readily soluble in water though less so than 

 oxy-hsemoglobin, and the solution, unlike that of the latter substance, 

 yields a precipitate with basic lead acetate in presence of ammonia; 

 they are identical in percentage composition with those of oxy-hsemo- 

 globin. The behaviour of methsemoglobin towards reducing agents is 

 interesting and also important as affording a means of discrimination 

 between this substance and hsematin. If some ammonium sulphide be 

 added to an alkaline solution of methsemoglobin the mixture may be 

 observed to yield the spectrum of (reduced) hsemoglobin, and on now 

 shaking up with oxygen (air) it shows the spectrum of oxy-hsemoglobin. 

 When a solution of hsematin is similarly treated it yields the spectrum 

 of hsemochromogen (reduced hsematin) in alkaline solution (see below). 

 While the close relationship of methsemoglobin to oxy-hsemoglobin 

 is thus clearly shown, very great differences of opinion have existed as 

 to the exact nature of that relationship. Three views have been put 

 forward. 1. That methsemoglobin is more highly oxidised than 

 oxy-hsemoglobin. 2. That it is less highly oxidised. 3. That it is 

 united with exactly the same amount of oxygen as is oxy-hsemoglobin, 

 only in a more stable combination. The first view seems to have been 

 based on the ready production of methsemoglobin by oxidising agents, 

 and on the statement that when methsemoglobin is reduced it yields 

 first oxy-hsemoglobin and then hsemoglobin. The second view rested 

 on the possibility of obtaining methsemoglobin by the prolonged action 

 of a vacuum or the shorter action of palladium saturated with 

 hydrogen, and on the statement that by reducing agents it passes 

 at once to hsemoglobin without the intermediate appearance of oxy- 

 hsemoglobin. The third view, which now appears to be generally 



1 Hiifner u. Otto, Zt.f.physioL Chem. Bd. vn. (1883), S. 65. 



2 Hiifner, Ibid. Bd. vm. (1884), S. 366. Jaderholm, Zt. f. Biol Bd. xx. (1884), 

 S. 419. 



3 Haminarsten, quoted by Jaderholm, loc. cit. S. 422. 



4 Halliburton, Quart. Jl. Mic. Sci. Vol. xxvni. (1888), p. 201. Gives rapid 

 method for microscopic purposes. See his Chem. Physiol. and Pathol. p. 280. 



