514 Dr. E. F. Armstrong. [Apr. 5, 



where E is the total enzyme, y the amount withdrawn in combination 

 with the products in time t. 



During the period when the proportion of sugar present is very 

 large, x becomes negligible compared with S, so that 



S = KS = *< 



where h is a constant. 



The apparent duration of the linear period must be affected not 

 only by x becoming no longer negligible compared with S but also 

 by the extent to which the products of change make their influence 

 felt. 



It may here be pointed out that Henri's formula combines in a 

 single expression the linear and logarithmic periods, but does not take 

 into account the last period during which the products of the change 

 exercise a retarding influence. 



All these points are brought out not only in the results given in 

 this paper but also in those tabulated by Brown and Glendinning. 

 Although these observers have called attention to the existence of 

 a linear period followed by a " logarithmic " period, they have failed 

 to point out the meaning which may be attached to the decrease in 

 the values of K observed during the latter stages of hydrolysis, when 

 the products exercise a marked influence. 



Their experiments afford an example of such an influence. Thus 

 in Table IV,* referring to the hydrolysis of a 3 per cent, solution 

 of starch by diastase at 21°, the value of K will be seen to increase 

 until about half the starch was hydrolysed and then to decrease. If 

 the value after 60 minutes be made the new starting point and the 

 values be recalculated in the manner adopted by Brown and 

 Glendinning,! the followin^figures are obtained : — 



«*- 



Old time units. * New time units. K . 



60 minutes — — 



80 „ 20 minutes 458 



100 „ 40 „ 461 



120 „ 60 „ 448 



140 „ 80 „ 410 



It is evident that whereas K should be a constant if the period 

 were " logarithmic," it begins to decrease after about 66 per cent, of 

 the starch has been hydrolysed : showing that the influence of the 

 products in removing enzyme has begun to make itself felt. 



The action of invertase appears to be much less affected by invert 



* Loc. ext., p. 400. 

 f Loc. cit. t p. 393. 



