342 



Prof. H. E. Armstrong and others. [Jan. 1, 



Diagram 18. 



I00r 



20 40 60 80 100 120 



" law of mass action " and to assume that the rate at which action takes 

 place is such that it is proportional at any moment to the amount of 

 substance left unchanged. It should be possible, therefore, to express the 

 rate of such changes by logarithmic curves but it is recognised that the 

 products of change have a more or less marked retarding influence and that, 

 on this account, the actual curve expressing the rate of change always falls 

 below the theoretical curve. It is further supposed that the action is 

 reversible and that therefore, on this account, the change is never complete, 

 though it may be very nearly so in dilute solutions. Lastly, it is recognised 

 that when the enzyme is present in very small proportion, the action 

 proceeds at a nearly constant rate : also that it is much retarded in very 

 concentrated solutions — a result ascribed by some to the viscosity of such 

 solutions. 



It appears to us that our results are not in accord with the views hitherto 

 accepted and that it is to be supposed that enzymic changes would be found 

 to take place at approximately constant rates were it not that they are subject 

 directly and indirectly to considerable retardation by the products of change ; 

 indeed it is probable that the products of change have an affinity for the 



