SELIG HECHT 



503 



decrease amounts to no less than 61 per cent of the initial threshold 

 value. A glance at Fig. 2 and at Table I, presented later in this 

 paper, shows that the minimum intensity, — the data actually ob- 

 tained, — varies in no such way as indicated by Fig. 1. The data of 

 Fig. 2 are the same as those forming the basis of Fig. 1. 



ZOflOO 



/o zo JO -40 so 



00-6— OO—O 



oo- 



so 



eo 



^O 30 '40 



77 me — /^/nufes 

 Fig. 2. The course of dark adaptation expressed in terms of the minimum in- 

 tensity visible to the eye. The data are the same as in Fig. 1. The lower por- 

 tion of the curve is redrawn in the inset, using a magnified scale of ordinates. 

 The exceedingly great change in the intensity during the first 10 minutes is clearly 

 apparent. 



