124 



THE NATURE OF FOVEAL DARK ADAPTATION 



less or more sensitive than another. However, the shape of the 

 curve of dark adaptation remains the same, and the degree of varia- 

 tion is not much more than would be expected from inspection of 

 the points in Fig. 2. To show this, I have plotted in Fig. 3 the re- 

 sults of the first five subjects. The other ten subjects give exactly 

 the same kind of data. Each point in Fig. 3 is the average of two 

 readings, one for the left eye and one for the right. It is apparent 



:^ 



200 -4^0 600 BOO 



Dora f ion of dark adaptation — seconds 



Fig. 3 

 readings, 



Data for the first five subjects. Each point is the average of two 

 one for the left, and one for the right eye. 



that the experiments are reproducible not only in a given individual, 

 but in a group of individuals as well. In presenting the complete 

 data I have therefore combined the measurements of the fifteen sub- 

 jects, thus getting an average of thirty determinations of each of the 

 ten points on the curve of dark adaptation. These average results 

 are given in Fig. 4. It will be seen that the shape of the curve and 

 the location of the average points are similar to those shown for the 

 single points in Figs. 2 and 3. 



