ANIMAL OXIDATIONS. 449 



tunately, we must again state that we are now dealing entirely with 

 hypotheses, and that we are not yet in position to explain with certainty 

 the exact nature of the processes which are brought about by the action 

 of oxidizing ferments. 



Traube * suspected the formation of hydrogen peroxide. In the oxida- 

 tion of readily oxidizable substances, instead of the oxygen molecule being 

 merely split and active oxygen set free, he imagined that water is first split 

 off. The hydroxyl group in the latter then combines with the oxidizable 

 substance, R, and the free hydrogen atom combines with neutral oxygen, 

 forming hydrogen peroxide: 



R + 2 H 2 + O 2 = R(OH) 2 + H 2 O 2 . 



Hydrogen peroxide is a strong oxidizing agent, and will attack the diffi- 

 cultly oxidizable substances. 



The above process may be supposed to take place somewhat differently. 

 Perhaps the readily oxidizable substance (R) combines with the oxygen, 

 and forms itself a peroxide. The latter can then give up its extra atom 

 of oxygen to some difficultly oxidizable substance (Ri) . 2 



R + 2 = RO 2 . RO 2 + Ri = RO + 



In this case the peroxide takes the place of the hydrogen peroxide, and 

 has the same effect. According to this theory it is not that we have active 

 oxygen present, but rather that the oxygen in the peroxide is held in a 

 loosely combined condition from which it is easily set free. 



The question now arises, What connection do the ferments have with this 

 peroxide formation? We can imagine that the ferment itself combines 

 with oxygen, and by forming a peroxide thus acts as a carrier. In 

 fact, such an action has been assumed, and A. Bach with R. Chodat 3 has 

 supported the assumption by quite a number of experimental observa- 

 tions. These authors carried out their investigations with plants. They 

 separated the ferments which take part in oxidations into three classes. 

 First, there are albumin-like substances which form peroxides from the 

 oxygen that is brought to the tissues by the blood. Such ferments they 

 designate as oxygenases. Then Bach and Chodat identified peroxydases, 

 ferments which have the power of increasing the peroxidation power of 

 the former. Finally, in each cell there are present, according to these 

 authors, catalases, which decompose hydrogen peroxide catalytically with 

 evolution of oxygen. 



1 Ber, 10, 1111 (1886); 10, 1115; 22, 1496 and 3057 (1889); 26, 1471 and 1476 

 (1893). 



a C. Engler and W. Wild: Ber. 30, 1669 (1897). 



3 Biochem. Zentr. 1, 417 and 457 (1903). A. Bach: Berichte, 38, 1878 (1905); 37, 

 3785 (1904). Bourquelot: Compt. rend, de la soc. biol. 49, 402 (1897). Batelli and 

 Stem: Compt. rend. 140, 1197 and 1352 (1905); 141, 139 (1905). 



