CATALYSTS AND ENZYMES 127 



were made with great ingenuity, and to acknowledge that the 

 errors to which they led were due to the stage of advancement 

 of scientific knowledge at the time, and not to want of care on 

 the part of the experimenter. 



The indisputable proof by Pasteur and others that fermenta- 

 tion is due to the life processes of micro-organisms and the strong 

 position which Liebig took in combating this led to his theory 

 that catalytic activity was due to the activity of one body being 

 transferred to another, and so to the catalysis of the latter, fell 

 into disrepute, until it was revived by Nageli in the form of the 

 theory that the decomposition by a ferment is due to a transference 

 of " molecular vibration " from the ferment to the substratum. 

 The molecules of the substance undergoing the fermentation were 

 supposed to be already in a condition of vibration, which became 

 increased by the sympathetic swingings or vibrations in the 

 ferment to such an extent that the vibrations passed the point 

 of equilibrium, and the substance accordingly underwent de- 

 composition. This revival of a part of Liebig's view by Nageli 

 was only applied by him to the organised ferments, and he stated 

 that it was the living protoplasm which acted directly in in- 

 creasing the molecular vibrations. He maintained the view that 

 the living cell and the enzyme were different both in mode of 

 action and in their physiological role, the enzymes preparing 

 the food-stuff* for use in physiological activity, and the 

 organised ferment or living cell making use of the material so 

 prepared. 



It is now clear that Liebig was wrong in regarding the yeast 

 as being in a process of decay and giving rise to accompanying 

 chemical changes in the substratum which lay apart entirely from 

 any life processes. 



But if we strip Liebig's statements free from this error there 

 is much in them which even to-day demands attention. 



We shall see later that no single theory which has ever been 

 put forward is capable of accounting for all cases or classes of 

 catalytic action, and it is quite probable that catalysis is due in 

 one case to one cause or factor, and in another case to quite a 

 different one, so that different theories may by no means be 

 incompatible. 



It seems to the writer that for those cases of almost instan- 

 taneous reaction due to mechanical vibration or friction, or to 



