PEROXIDASE-LIKE ACTION OF HAEMOGLOBIN 543 



concentration and the erythrocytes at still higher degree of 

 concentration of hydrogen peroxide. 14 Another and per- 

 haps seemingly impertinent question, however, is whether 

 it is actually worth the trouble to devote so interminably 

 great an amount of work to these matters. The author's 

 personal views on the subject may be deferred until after 

 the presentation of the problems of the peroxidase-nature 

 of haemoglobin and of the artificial peroxidases. 



Peroxidase-like Action of Hcemoglobin. The question 

 may be at once considered whether there is a special funda- 

 mental difference between the oxygen carrying action of 

 haemoglobin and that of the true peroxidases. 



As this peroxidase-like action of haemoglobin is also 

 characteristic of its color constituent, hsematin, but as the 

 latter is in the fullest sense a thermostable substance, it 

 might well be believed that there can be no suggestion of iden- 

 tity, because the peroxidases in accordance with their ferment 

 character must necessarily be thermolabile substances. For- 

 merly this was the common opinion ; and it is true that gener- 

 ally when a tissue containing peroxidases is boiled its effici- 

 ency in this direction is seen to disappear. This, however, 

 cannot be regarded as establishing a fundamental difference, 

 as von Czyhlarz and the author, 15 and other observers as 

 well, have occasionally dealt with peroxidase solutions which 

 retained their activity almost at the boiling temperature. 

 Battelli and Stern in their peroxidase experiments with 

 formic acid have noted an increase of activity with increase 

 of temperature up to 38-40 C. But from this point further 

 increase of temperature caused a lowering of oxidation, 

 which stopped almost completely at 65 C. ; while the oxida- 

 tion of formic acid by haemoglobin in the presence of hydro- 

 gen peroxide is distinctly more active at a temperature of 55- 



14 R. Fischel, Wiener klin. Wochenschr., 23, 1557, 1910; cf. also F. Winkler, 

 Folia Haematol., 4, 323, 1907 ; 5, 17, 1908. 



16 E. v. Czyhlarz and O. v. Furth, 1. c., p. 367; cf. A. van der Haar 

 (Utrecht), Ber. d. deutsch. chem. Ges., 43, 1321, 1910. 



