47 
oxygen in these changes, and attributed the bluing of guaiacum by 
plant tissues to a peculiar unstable principle which he called cyanogene. 
After the work of Priestley and Lavoisier, the greatest impetus to 
a better understanding of the processes of oxidation was given by the 
discovery of ozone by Schoenbein in 1840. We have seen that this 
observer recognized this active variety of oxygen among the products 
of slow oxidation, and that he explained the phenomenon of oxygen 
carrying as due to the production of ozone or of an ozonide. He 
greatly extended our knowledge of the bluing of guaiacum, and also 
the earlier observations of Planche on the presence of oxygen exciters 
in plants and animals, and he accounted for the remarkable oxidizing 
activity of such substances on the supposition that they, in common 
with platinum, nitric oxide, and other oxygen carriers, ozonize the air, 
combining with the ozone thus produced to form an active ozonide, 
which in turn can give up its oxygen to other less readily oxidizable 
substances. These were his Sauerstofferregern and Sauerstofftrdgern. 
They are what we to-day term the oxidases, or oxidizing ferments. 
Through the action of these substances on certain chromogens he was 
able to explain the changes of color observed in the growth and decay 
of certain species of the higher fungi, and similar changes occurring 
in certain fruits, such as take place in the apple when peeled or 
crushed. He also recognized the wide distribution of substances 
capable of decomposing or catalyzing hydrogen peroxide and of 
greatly activating the latent oxidizing powers of this substance; and 
all of these facts he was able to explain more or less satisfactorily in 
terms of his theory respecting the relation existing between common 
oxygen, ozone, and antozone, according to which ozone and antozone 
were oppositely electrified; that under the influence of various sub- 
stances, like platinum, etc., common oxygen and antozone or an anto- 
zonide could be transformed into ozone or an ozonide, and finally 
that ozone could react with an antozonide,such as hydrogen peroxide, 
to form common oxygen. In this connection it may be observed that 
no one can read the writings of Schoenbein without being impressed 
with the great wealth of his observations, and his theory regarding 
the nature of ozone will always serve to remind the thoughtful student 
of chemistry how clearly and apparently how accurately a great 
variety of phenomena can ofttimes be explained by an hypothesis 
altogether erroneous in its premises. 
It is evident , therefore, that during the first period, covering approxi- 
mately the first six decades of the nineteenth century, the presence of 
oxygen activators and carriers in the plant and animal world had been 
recognized, and the more important characteristics of the oxidases 
and peroxidases had been discovered, so far as we have an accurate 
knowledge of these properties to-day, and yet the terms “oxidase” 
and “oxidizing ferment” had not up to this time been introduced into 
