442 LECTURE XIX. 



ozonizing atmospheric oxygen. The cells take up the ozone, and then as 

 the latter breaks down to ordinary oxygen, the extra atom of oxygen 

 attacks some oxidizable substance. The assumption that as a matter 

 of fact there is an ozone formation in the tissues, meets with certain diffi- 

 culties. Relatively small amounts of ozone are poisonous to the cells. It 

 has never been possible to detect the presence of ozone in either plant or 

 animal organisms. So this hypothesis was soon abandoned. The assump- 

 tion that active oxygen is present in the tissues, is far more probable. 

 Hoppe-Seyler, 1 who suggested this hypothesis, based it upon the fact, 

 that in the animal tissues energetic reduction processes take place, side by 

 side with the oxidations. In this way, reducing substances are formed 

 which unite with one atom in the oxygen molecule, setting the other atom 

 free in an active condition. The butyric acid fermentation of sugar is an 

 example of such a reduction process. Hydrogen is set free: 



C 6 Hi 2 O 6 = C 3 H 7 COOH + 2 CO 2 + 2 H 2 . 



A support for the assumption that active oxygen causes the animal 

 oxidations, is furnished by the theory of nitrification. In this case also, 

 it is assumed that the organism, to whose activity the formation of nitrate 

 is due, first of all produces readily oxidizable substances, which then decom- 

 pose the atmospheric oxygen molecule, and thus form active (nascent) 

 oxygen for the oxidation of the nitrogen. 



The formation of such readily oxidizable substances which under normal 

 conditions are immediately oxidized further, is likewise indicated by the 

 so-called " spontaneous combustion " of hay. In this case, on account 

 of insufficient ventilation, such readily oxidizable substances collect in 

 considerable amount, and are suddenly oxidized as soon as fresh air 

 enters. 



If we are to believe that the oxidations in the animal organism take 

 place in this way, we must assume that first of all the food is hydrolyzed, 

 and that easily oxidizable compounds are formed which are oxidized by 

 the oxygen, received by the tissues from the blood, and at the same time 

 a part of this oxygen is activated. This nascent oxygen unites with the 

 more difficultly oxidizable substances. The first stage in the oxidation 

 of the food is, therefore, a hydrolysis; and inasmuch as the last-mentioned 

 process is brought about by means of ferments, these play a part in the 

 entire phenomenon of oxidation. This assumption has much in its favor, 

 and corresponds to certain discoveries. With its help we are able to under- 

 stand, for example, why the diabetic cannot oxidize d-glucose, and only 

 this one substance. We have simply to assume that the ferment is absent 

 which hydrolyzes this sugar so that oxygen does not come in contact with 



Pfliiger's Arch. 12, 16 (1876). 



