492 CHEMISTRY OF THE PROTEIDS CHAP. 



many other reagents. Dittrich l has shown that both oxidising 

 substances ozone, iodine, chlorates, permanganates, nitrates, potassium 

 f erricyanide ; and reducing bodies nascent hydrogen, palladium 

 hydrate, nitrites, pyrogallol, allantoin, hydroquinone, etc. ; as also 

 other compounds anilin, toluidin, acetanilid, acetphenetidin, glycerine, 

 etc., lead to the formation of methaemoglobin. Haldane has shown 

 that the methaemoglobin formed by the action of nitrites on haemoglobin 

 is mixed with NO -haemoglobin. 2 The best method for preparing 

 methaemoglobin is to act on oxyhaemoglobin with potassium ferri- 

 cyanide, according to Hiifner, 3 Kiilz, 4 Otto, 5 v. Mering, 6 Jaderholm, 7 

 v. Zeynek, 8 and Hiifner. 9 



Acid-haemoglobin, which Harnack considers to be a definite sub- 

 stance formed along with methsemoglobin, is discussed on p. 495. 



The conversion of oxyhaemoglobin into methaemoglobin may also 

 occur in the living blood, 10 provided that the substances have the 

 power of entering the blood - corpuscles, as can, for example, 

 amyl-nitrite, dinitrobenzene, and antifebrin ; the chlorates can enter 

 the corpuscles of the cat, dog, and man, but not those of rabbits and 

 other herbivora (Haldane), and potassium ferricyanide cannot enter at 

 all. Haldane, 11 Makgill, and Mavrogordato have shown that in 

 poisoning with nitrites, dinitrobenzene, etc., which also form methaemo- 

 globin in the blood, death occurs from want of oxygen, exactly as in 

 CO-poisoning. To Haldane's researches into the action of ferricyanides 

 on oxyhaemoglobin attention has already been drawn in connection 

 with the determination of the oxygen capacity of blood (see p. 483). 

 The chemical changes induced by potassium ferricyanide Haldane 

 explains thus : " If ferricyanide be added to diluted blood, it will be 

 found that the solution now gives with ferric chloride a blue colour 

 indicating the presence of ferrocyanide. Evidently, therefore, the 

 ferricyanide is reduced to ferrocyanide. The oxygen rendered avail- 



1 P. Dittrich, Schmiedeberg's Arch. f. experiment. Path. u. Pharm. 29. 247 (1891). 



2 J. Haldane, Journ. of Physiol 21. 160 (1897). 



:{ G. Hiifner, Zeitschr. f. physiol. Ohem. 8. 366 (1884). 



4 G. Hiifuer and K. Kiilz, ibid. 7. 366 (1883). 



5 G. Hiifuer and J. G. Otto, ibid. 7. 65 (1882) ; J. G. Otto, Pfl&ger's Archiv f. d. 

 ges. Physiol. 31. 245 (1883). 



6 v. Mering, Zeitschr. f. physiol. Ghem. 8. 186 (1883). 



7 AxelJaderholm, Zeitschr. f. Biologic, 16. 1 (1880) ; 20. 419 (1884). 



8 R. v. Zeyiiek, Archiv f. (Anat. und] Physiol. 1899, p. 460. 



9 G. Hiifner, ibid. 1899, p. 491. 



10 v. Meriug, Zeitschr. f. physiol. Ghem. 8. 186 (1883) ; P. Dittrich, loc. cit. ; 

 A. Dennig, Deutsch. Arch. f. klin. Medizin, 66- 524 (1900) ; according to Maly's 

 Jahresberichten, 30. 169. 



11 J. Haldane, R. H. Makgill, and A. E. Mavrogordato, Journ. of Physiol. 21. 160 

 (1897). 



