Discussion 



37 



large quantities in which case, under any reasonable circumstances, the 

 percentage of inactivation is quite small, whether your reaction is 

 direct or indirect. The other case is the possibility of enzymes being 

 present in very small amount; as Mcllwain has shown (1946, Nature, 

 Lond., 158, 898), the possibility exists of enzymes being present only 

 to the extent of a few molecules per cell. But the situation is also 

 difficult there because the chance of a unique molecule of an enzyme 

 being inactivated is correspondingly small. So that in either case it seems 

 to me that the possibility of an enzymic explanation of metabolic effects 

 is not a very favourable one. 



