Chapter II. 
THE OXIDIZING FERMENTS. 
In its present shape, therefore, the peroxide theory of oxidation 
accounts for the phenomena of autoxidation and oxygen carrying 
upon the supposition that spontaneously oxidizable substances have 
the power of combining with partially dissociated molecules of oxygen 
to form peroxides. These peroxides may then react either with addi- 
tional amounts of the aut oxidizable substance itself or with some 
other substance to form simpler oxides. Thus, it may happen that as 
the result of its oxidation one substance. A, may effect the oxidation 
of a second substance, B , which latter is not directly oxidizable imder 
ordinary conditions. In this way the modern theory of oxidation 
affords a simple explanation of the formation of peroxides and of the 
phenomenon of oxygen carrying. 
The numerous applications of this theory are by no means confined 
to the inorganic world. In the life cycle of the plant and animal we 
meet with many changes which, in so far as oxygen is involved, find 
their simplest explanation in terms of this hypothesis. The affinity 
for oxygen which is displayed not only by the warm-blooded animals, 
but even by plants, is often remarkable. That such is the case may 
be gathered from the fact that Phipson ( 320 ) in 1896 employed one of 
the higher fungi, Agaricus atramentarius , as an agent wherewith to 
effect the analysis of atmospheric air. It has so happened, therefore, 
that in the history of our science both a mouse and a mushroom have 
been employed as oxygen absorbents wherewith to determine the 
quantity of oxygen in atmospheric air. During the absorption of 
oxygen by plants various substances are produced which are capable 
of effecting oxidations which ordinarily can not be brought about by 
molecular oxygen alone, such, for example, as the bluing of guaiaeum, 
the conversion of hydroquinone into quinone, the liberation of iodine 
from potassium iodide, etc. Like many of the chemical agents of the 
living cell, these powerful oxidizing substances are characterized by 
great instabilitv. Tliev are destroved bv heat and mineral acids and 
by various poisons, such as hydrogen cyanide, sulphur dioxide, phe- 
nylhydrazin, etc. It is claimed by some observers that they act 
catalytically, and hence are believed to partake of the nature of fer- 
ments. These substances are the oxidases, a or oxidizing ferments, 
Q The following general references to the literature of this subject will be found of 
interest in this connection: Remarques sur les matieres oxvdantes, que l’on peut 
rencontrer chez les etres vivants, by Bourquelot ( S5 ); Ueber Oxydationsfermente, by 
( 31 ) 
