494 CHEMISTRY OF THE PROTEIDS 



Bohr 1 distinguishes several modifications of haemoglobin, which 

 differ from one another in their oxygen-capacity, and has called these 

 modifications a-, f$-, y-, S-hsemoglobin. He has noticed similar 

 differences also in living blood, but Hiifner 2 has suggested that Bohr's 

 observations depend on a partial conversion of haemoglobin into met- 

 hiemoglobin or similar compounds. Marchand 3 has likewise described 

 phenomena which speak for a gradual conversion into methsemoglobin. 



Methaemoglobin, either as solid or in acid or neutral solutions, is 

 not red as is oxyhasmoglobin, but brown, like English porter ; in 

 alkaline solutions it is, however, red. Hiifner 4 was the first to prepare 

 it in a pure crystalline form from dog's, pig's, and horse's blood, after 

 Gamgee had already succeeded in 1868 in obtaining crystals in com- 

 bination with nitrites. Pure crystals resemble grey-brown, doe- 

 coloured needles with a peculiar silky lustre. The method used fcr 

 preparing methsemoglobin crystals is the same as that used for oxy- 

 hsemoglobin, after the latter has been converted into metha3moglobin 

 by a little potassium ferricyanide. It has the same composition as 

 oxyhsemoglobin, see p. 493. 100 ccm. water dissolve 5,851 grm. 

 at ; and much larger quantities at higher temperatures. 



Methsemoglobin possesses in acid arid in alkaline solutions different 

 spectra, which have been investigated most carefully by Jaderholm, 5 

 Araki, 6 Gamgee, 7 and Haldane. In acid solutions it possesses two 

 bands ; the first very marked band in the red-orange, between C and 

 D and close to C, with its greatest intensity, according to 



Gamgee, .... A633 A623, 

 Araki, .... A648 A629, 

 Dittrich, 8 .... A632. 



A feebler band which, examined by the spectro- photometric 

 method of Hiifner, is, however, as intense as the other lies in the 

 bright blue region of the spectrum between G and F, close to F : 



A500 A495. 

 If methremoglobin is not in acid solution, or not quite free from 



1 Chr. Bohr and Sophus Torup, Skand. Arch. f. Phys. 3. 69 (1891) ; Chr. Bohr, 

 .ibid. 3. 76, 101 (1891); Fr. Tobiesen, ibid. Q. 273 (1895); Chr. Bohr, Zentralbl.f. 

 Physiol. 4. 249 (1890). 2 G. Hiifner, Arch.f. (Anat. u.) Physiol. 1894, p. 130. 



3 F. Marchaud, Virchow's Arch. 77. 488 (1879). 



4 G. Hiifiier and J. G. Otto, Zeitschr. f. physiol. Chem. 7. 65 (1882) ; G. Hiifner, 

 ibid. 8. 366 (1884) ; G. Hiifner, Arch. f. (Anat. u.) Physiol. 1899, p. 491 ; E. v. 

 Zeynek, ibid. 1899, p. 460. 



5 Axel Jaderholm, Zeitschr. f. Biolocj. 16. 1 (1880) ; 2O. 419 (1884). 



6 Tr. Araki, Zeitschr. f. physiol. Chem. 14. 405 (1890). 



7 A. Gamgee, Zeitschr. f. Biolog. 34. 505 (1896). 



8 Paul Dittrich, Schmiedeberg s Arch.f. experini. Pathol. u. Pharmak. 29. 247 (1891). 



