METH^MOGLOBIN. 277 



into oxyhsemoglobin and then into haemoglobin by reducing substances, 

 while others (HOPPE-SEYLER and ARAKI 1 ) dispute this. 



According to HUFNER and REINBOLD - \ gram methsemoglobin can 

 take up 2.685 cc. nitric oxide. 



Methsemoglobin crystallizes, as first shown by HUFNER and OTTO, 

 in brownish-red needles, prisms, or six-sided plates. It dissolves easily 

 in water; the solution has a brown color and becomes a beautiful red 

 on the addition of alkali. The solution of the pure substance is not 

 precipitated by basic lead acetate alone, but by basic lead acetate and 

 ammonia. The absorption-spectrum of a watery or acidified solution 

 of methsemoglobin is, according to JADERHOLM and BERTIN-SANS, very 

 similar to that of haBmatin in acid solution, but is easily distinguished from 

 the latter since, on the addition ol a little alkali ana a reducing substance, 

 the former passes over to the spectrum of reduced hemoglobin, while 

 a hsematin solution under the same conditions gives the spectrum of an 

 alkaline ha3mochromogen solution (see below). According to ARAKI 

 and DITTRICH, a neutral or faintly acid methaBmoglobin solution shows 

 only one characteristic band, a, between C and D, whose middle corresponds 

 to about ^ = 634. The two bands between D and E are only due to con- 

 tamination with oxyha3moglobin (MENZIES, LEWIN, MIETHE and STEN- 

 GER. 3 MethaBmoglobin in alkaline solution shows two absorption-bands 

 which are like the two oxy hemoglobin bands, but they differ from these 

 in that the band /? is stronger than a. By the side of the band a and 

 united with it by a shadow lies a third fainter band between C and D, 

 near to D. (Spectrum Plate 4) . 



The claims as to the action of sodium fluoride upon haemoglobin and methaeino- 

 globin are somewhat contradictory. 4 



Crystallized methemoglobin may be easily obtained by treating a con- 

 centrated solution of oxyhsemoglobin with a sufficient quantity of con- 

 centrated potassium-ferricyanide solution to give the mixture a porter- 

 brown color. After cooling to C. add one-fourth vol. cooled alcohol 

 and allow the mixture to stand a few days in the cold. The crystals may 

 be easily purified by recrystallizing from water by the addition of alcohol. 



Cyanmethaemoglobin (cyanhaernoglobin) is, according to HALDANE, identical 

 with photomethsemoglobin (BOCK), which is produced by the influence of sun- 

 light upon a methsemoglobin solution containing potassium ferricyanide. It 

 was first carefully described by R. ROBERT and obtained in a crystalline form 



1 Jaderholm, Zeitschr. f. Biologie, 16; Saarbach, Pfluger's.Arch., 28; Araki, Zeit- 

 schr. f. physiol. Chem., 14. 



2 Arch. f. (Anat. u.) Physiol., 1904. Suppl. 



3 Jaderholm, 1. c.; Bertin-Sans, Comp. rend., 106; Dittrich, Arch. f. exp. Path. u. 

 Pharm., 29; Menzies, Journ. of. Physiol, 17; Lewin and collaborators, footnote 1, page 

 274. Important references on methaemoglobin are given by Otto, Pfluger's Arch., 31. 



4 Piettre and Vila, Compt. rend., 140; Ville and Derrien, ibid., 140. 



