450 LECTURE XIX. 



Substances which act catalytically upon hydrogen peroxide have been 

 known in nature for a long time. It was even known to Thenard 1 that 

 fibrin and the tissue of the kidneys and lungs were capable of decom- 

 posing hydrogen peroxide into water and oxygen just as energetically 

 as is done by platinum, gold, and silver. In milk 2 also, and in blood, 3 

 there is a hydrogen-peroxide-catalase. The catalases are evidently of 

 quite common occurrence. 4 Their significance is differently explained. 

 It is held that they tend to prevent the appearance of active oxygen. It 

 may be shown, for example, that urea and xanthine cannot be oxidized 

 by hydrogen peroxide in the presence of a catalase. They decompose 

 hydrogen peroxide with the formation of molecular oxygen. 5 In fact, the 

 catalases are not oxidizing ferments at all. They are not of themselves 

 able to turn tincture of guaiacum blue, nor in the presence of hydrogen 

 peroxide. Thus the cells evidently possess a means of restricting and 

 regulating the activity of the oxidation processes taking place within 

 them. 



The action of the oxygenases appeared to have a very simple explana- 

 tion, when it was found that their ash contained substances which of 

 themselves could act as carriers of oxygen. Thus Bertrand 6 found 2 . 5 

 per cent of manganese in the ash from laccase. Manganese salts are 

 very active carriers of oxygen. In other oxidases iron is present. Ber- 

 trand compared . 1 gram of ferment in 50 cubic centimeters of quinol 

 solution in its action first with manganese alone and then with a man- 

 ganous salt plus the ferment. 



Manganous salt alone 0.3 c.c. oxygen absorbed 



Laccase, from Lucerne, alone . . . .0.2 c.c. oxygen absorbed 

 Laccase plus manganous salt . . . .6.3 c.c. oxygen absorbed 



These inorganic constituents have been assumed to combine with albu- 

 min, and form a dissociable compound. The metal constituent serves to 

 carry the oxygen and in much the same way as we described for the 

 oxidation of sugar in alkaline solution by means of copper oxide. The 

 manganese is, according to this view, originally present in the divalent or 

 manganous form, which takes up oxygen from the tissues with the forma- 

 tion of tetravalent manganese (corresponding to the manganese dioxide 

 type) , and the other atom in the oxygen molecule is carried to the oxidizable 



Ann. chim. et physiol. (2) 11, 85 (1819). 



P. Raudnitz: Zentr. Physiol. 12, 790 (1899); Z. Biol. 42, 91 (1901). 

 George Senter: Z. physikal. Chem. 44, 257 (1903), and 61, 673 (1895); Proc. of the 

 Roy. Soc. 74, 201 (1894). 



O. Loew: Z. Biol. 43, 256 (1902). 



Philip Shaffer: Am. J. Physiol. 14, 299 (1905). 



Compt. rend. 124, 1032, 1055 (1897). 



