332 I'K/XC/J'LES OF GENERAL PHYSIOLOGY 



inactive, and are then known as " xyniogens.'' These are converted by certain 

 agents into the active enzymes, a change which does not appear to be reversible. 



While many enzymes seem to be very "specific," or selective, in that their 

 effect on one particular substrate is very much greater than on any other, it 

 is necessary to be cautious in assuming this as being unconditionally true. 

 Further investigations are needed of the changes in the action of en/.yme> 

 produced by different conditions. There is also, in many cases, evidence that the 

 same enzyme may act on different substrates at such different rates that it appeals 

 to act only on one, unless prolonged observations are made, but the reason why 

 the rate is faster in the one case requires elucidation. Optical isomerism certainly 

 plays a part. 



LITERATURE 



Mass Action. 



Mellor (1904, pp. 177-184). Nernst (1911, pp. 438-447). 



Catalysis in General. 



Mellor (1904, Chapter X. ). Woker (1910). 



Nature of Enzyme Action. 

 Bayliss (1913, 2). 



Kinetics of Enzyme Action. 

 Herzog (1910). 



Action of Individual Enzymes. 

 bppenheiim-r (1909). 



Synthetic Action. 



Bayliss (1913, 1). 



