INTRODUCTION 11 



to use the curve for finding values by means of 

 interpolation. 



Therefore in all the curves which represent the 

 velocity of reaction as dependent on temperature, I 

 have taken as the ordinate y = \og K, and when the 

 interval of temperature was relatively great, I have 

 drawn the curve giving the exact equation (see 

 Fig. 10). Something similar has been done when 

 the progress of digestion with time (cf. Fig. 8) has 

 been graphically represented. In this case the 

 square root of the time, *J~t, has been chosen as 

 abscissa. If the rule of SCHUTZ were absolutely 

 strict the representative curves, giving the digested 

 quantity as ordinate, ought to be straight lines. But 

 this is only approximately true ; it holds only for 

 small values of the time t. This is easily verified 

 by the eye if we follow the curve representing the 

 exact formula, and drawn in the figure, down to 

 values in the neighbourhood of the origin. 



In the diagrams, indicating the change of the 

 velocity of reaction, K, with temperature, I have 

 drawn many lines representing different substances. 

 This has been done in order to save space and also 

 to give a more general view of the phenomenon re- 

 presented. But this concise representation has only 

 been possible by changing the origin. This is 

 indicated for each curve by a formula expressing how 

 many centigrade degrees of temperature have to be 

 added to that given by the abscissa, in order that 

 the figures may represent the observations. In one 

 case the scale is reduced to the half magnitude, which 



