SELIG HECHT 



129 



In Fig. 5 are given the results calculated from the diameter values 

 in Table IV of Reeves ' paper. From the smoothed curve it is simple 

 to find the pupil areas corresponding to the points plotted in Fig. 4. 

 It is not necessary to correct for the effect of the cornea on the apparent 

 size of the pupil, because we are interested in the relative variation in 

 the pupil area. Calling unity the area of the pupil after 7.1 seconds 

 dark adaptation, the first point in Fig. 4, 1 have computed the relative 

 areas of the pupil for the different points in Fig. 4. These values are 

 given in Table II. 



^ JO 



5 



1^ 



O so /OO ISO zoo 3SO 300 



Duratforj cf dark actapfafiorj'^ seconds 



Fig. 5. Change in the area of the pupil during dark adaptation. The data 

 are computed from the diameters given in Table IV of Reeves' (1918) paper. 



In the last column of the same table are given the values of the 

 products of the measured intensity into the relative area of the pupil. 

 These numbers represent the intensity thresholds at different times 

 in the dark on the assumption that the pupil area has maintained a 

 constant area equal to its value at 7.1 seconds. This point is chosen 

 arbitrarily because it is the first accurately measured point in these 

 experiments. Any other point would have done just as well, because 

 all that we arc concerned with are the relative changes at constant 



