CHAPTER XIII 



THEORIES AS TO MODE OF ACTION OF CATALYSTS AND 

 ENZYMES 



CORRELATION OF THEORIES MEANS OTHER THAN CATALYSIS BY 

 WHICH CHEMICAL REACTIONS CAN BE INDUCED, OR REAC- 

 TION VELOCITY VARIED. 



I. The Theory of Molecular Vibrations. Theories having a bear- 

 ing upon catalytic action first began to be formulated for the 

 purpose of giving some explanation of the processes of fermentation 

 which at the time occupied the attention of the chemist more 

 than of the biologist. The brilliant work of Pasteur had not as yet 

 illuminated the action of micro-organisms in these processes, when 

 Liebig, searching for some explanation of the action of yeast upon 

 glucose, evolved the theory that such action arose because the 

 yeast was itself involved in a process of chemical activity or decay 

 and provoked as a result chemical activity in the sugar. In support 

 of his theory Liebig adduced many examples from inorganic 

 chemistry of where the chemical activity of one body influences 

 that of another, and of cases where even mechanical vibration 

 causes changes, as in explosive bodies, such as the iodide or chloride 

 of nitrogen. 



It is not to be wondered at that Liebig in those early days 

 looked upon those activities, which are now known to be due to 

 micro-organisms, as due to chemical action entirely. 



Many of the experiments carried out by Liebig and others of 

 his school of thought, to attempt to exclude the possibility of 

 micro-organisms being present, were well and scientifically thought 

 out, and if they led the distinguished chemist into error, it was 

 only because of failure to realise, at that early date, the difficulty 

 not only of maintaining but of preserving complete sterility. When 

 one reads the experiments by which it was sought to prove that 

 it was the access of air and not the presence of micro-organisms 

 which conditioned fermentation, one is forced to admit that they 



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