448 LECTURE XIX. 



lively established. The oxydase which takes part in breaking down the 

 nucleins also belongs here. 1 



In this class of oxidizing ferments we must also reckon the ferment of 

 the acetic acid bacteria, discovered by E. Buchner and J. Meisenheimer. 2 

 Quite independently of the other activity of these microbes, this ferment 

 changes alcohol into acetic acid: 



CH 3 . CH 2 OH + O 2 = CH 3 . COOH + H 2 0. 



Unquestionably, a great many other oxidations are to be traced to the 

 action of oxidizing ferments, and we find in the literature numerous other 

 ferments described under particular names. We must not forget, how- 

 ever, that the identification of ferments is an extremely difficult task, and 

 it is very seldom that in any case it is absolutely proven a new one is at 

 hand. Thus we know from the investigations of Bertrand 3 that in the 

 juice of the berries of mountain ash a hexatomic alcohol, sorbitol, is present 

 which under certain conditions is changed to the hexose, sorbose. It would 

 be unjustifiable from this fact alone to assume that this evident oxidation 

 is to be attributed to the presence of a ferment. It has been, in fact, 

 established that a certain species of bacteria, Bacterium xylinum, which 

 is introduced into the berries by means of a tiny red flea, Drosophila 

 Junebris, causes this transformation. This bacterium will likewise oxidize 

 mannitol to fructose, xylose to xylonic acid, etc. Although it is indeed 

 very likely that these bacteria act side by side with oxidizing ferments, 

 still, on the other hand, it is not right to assume their presence until the 

 ferment itself has been isolated. 



We have intentionally made this digression in order that we may gain 

 some idea as to the way in which such oxidations are effected, and as to 

 the abundance of such ferments. Of course this has not told us much 

 concerning the " oxidative " breaking down of the most important food- 

 stuffs. At present we do not know exactly how and when the oxidation 

 takes place in the case of protein, fat, or carbohydrate. We can make 

 assumptions, but we know nothing with certainty. 



We have up to now concerned ourselves merely with the empirical 

 knowledge, and have not said anything as regards the way in which these 

 ferments act. Perhaps a glance at the mechanism of their action may 

 give us some idea of the oxidation as it takes place in the tissues. Unfor- 



1 See Lecture XIII, p. 293. 



2 Ber. 36, 634 (1903). 



3 Compt. rend. 122, 900 (1896); 126, 842, 984 (1898); 127, 124, 758 (1898). Con- 

 cerning the oxidation of glucose to gluconic acid, and of gluconic acid to oxygluconic 

 acid, see Bontroux: Ann. Pasteur, 2, 308 (1887); Compt. rend. 127, 1224 (1898). Oxi-_ 

 dation of quinic acid to protocatechuic. Emmerling and Abderhalden: Zentr. Bac- 

 teriol. Parasitenkunde und Infectionskrankheiten, 10, Abt. II, p. 337 (1903). 



