CHANGES IN FERMENTATION. 621 



However different the chemical process is in each of General view 

 the fermentations described, we can find some general a i process^ 

 points of resemblance in all the true fermentations, fermentation. 

 We everywhere observe a marked splitting up of the 

 fermentescible molecule, and an extensive re-arrange- 

 ment of the atoms. In all cases carbonic acid is formed, 

 and for this it is evident that new combinations between 

 carbon and oxygen are necessary, and these are rendered 

 possible by the solution of combinations between oxygen 

 and hydrogen, carbon and hydrogen, carbon and carbon.* 



In the fermentation of formic acid H Cx^ TT Wandering of 



V -tL the oxygen 



the union of the oxygen and hydrogen atoms in the atom * 

 hydroxyl group, and also that of the hydrogen and 

 carbon atoms, is broken up. The liberated hand of the 

 oxygen atom unites with the hand of the carbon atom 

 liberated at the same time ; the two hydrogen atoms 

 which are freed unite with one another, and thus C0 2 

 and H 2 are formed. In a similar manner, in all fermen- 

 tations there occurs a wandering of the oxygen atom 

 from the hydrogen to the carbon ; while, on the other 

 hand, by the separation of the C H and C C union 

 room is procured for the new attachment of the oxygen 

 to the carbon. In short, the group carboxyl is formed 

 while, on the other hand, reducing atomic groups, H 

 H or C H compounds, appear. In the whole move- 

 ment stronger affinities are grouped together, and 

 energy becomes free. Nevertheless, the wandering of 

 the oxygen atom which leads to the breaking up of 

 the molecule only occurs when the molecule is not 

 too large in relation to the number of the displaceable 

 oxygen atoms. If, as in the case of many benzole 

 derivatives, and in the higher fatty acids, numerous 

 carbon atoms are united with each other, w r hile only 

 one C H group is present which can form carboxyl, 

 no such wandering occurs in a molecule; on the 

 other hand, this wandering is possible when several 

 atoms can enter into new C combinations, as in the fer- 



* Hoppe-Seyler, Physiolog. Ckem., p, 124. Arch. f. d. ges. physiol, 

 vol. xii. 1. 



