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however, and in the presence of small amounts of hydrogen peroxide 
or ozonized oil of turpentine it has the power of effecting the oxida- 
tion of a considerable number of easily oxidizable substances. In 
other words, milk contains catalase and peroxidase. These have 
been referred to in the literature by these names ; and also more or less 
indiscriminately by certain writers as the oxidizing ferments of milk 
or superoxidases, and also by some as the indirect oxidases. 
Catalase . — From what is known of the wide distribution of the 
catalases among living things and plant and animal secretions it 
seems probable, although it can not be said to be known absolutely 
at present, that the fresh milk of all animals has the power of decom- 
posing hydrogen peroxide more or less easily. Jolles (20) has 
pointed out that human milk decomposes five or six times as much 
hydrogen peroxide in the same length of time and under the same 
conditions as cow’s milk. This author is inclined to attach consid- 
erable importance to this reaction, and recently Von der Velden (21) 
also lays emphasis on the fact that the presence of catalase in human 
milk serves to distinguish it from cow’s milk. On the other hand, 
the fact that cow’s milk can decompose hydrogen peroxide is attested 
by many observers, some of whom, among them Amberg (22), have 
called attention to the gradual disappearance of hydrogen peroxide 
in cow’s milk on standing, and others, van Itallie (23) among them, 
to the fact that cow’s milk loses its power to decompose hydrogen 
peroxide on heating to 63° C. Faitelowitz (24) has shown that the 
catalase of milk is associated with the fat globules. This has been 
confirmed by Reiss (25), who further points out that the catalase of 
milk is insoluble in the presence of colloids. 
In the present state of our knowledge we know very little concern- 
ing the function of catalase in living tissue and active secretions. The 
view has been advanced by Loew (26), who has made extensive 
studies in this field, that the function of catalase is to destroy any 
hydrogen peroxide that may have been formed during the respiratory 
processes in the living cell, thereby preventing the accumulation of 
this and other peroxides, all of which are more or less toxic in their 
effects, thus affording protection against a toxic product of respira- 
tion. The question whether hydrogen peroxide is formed in the res- 
piratory process in plants or animals is a much-mooted question, and 
there has been considerable difference of opinion among chemists as 
to whether hydrogen peroxide ever occurs in animal or vegetable tis- 
sues. One thing is certain, however, and that is, whether hydrogen 
peroxide occurs therein or not other complex peroxides do occur, espe- 
cially in plant tissues and exudations (see Bach’s (27) investiga- 
tions), and quite recently in an investigation of remarkable interest 
and far-reaching importance, Usher and Priestley (28) have confirmed 
ErlenmeyeFs (29) theory of the origin of carbohydrates in green 
