COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 57 



aroused by the stimulation of paracentral, never of peripheral, regions 

 of the retina. 



A comparison of the different series of phases tabulated above leads 

 one to believe that in many instances the series had not run its complete 

 course when the stimulation ceased. And this is particularly true of the 

 more central regions of the retina. It seems probable that the time 

 required for the complete chromatic adaptation (or fatigue) of a given 

 region varies with its distance from the fovea. 



(&) Variations of saturation and of color tone which result from changed condi- 

 tions of the local chromatic adaptation of the retina, i. e., which occur as the 

 result of previous stimulation. 



If in a series of experiments upon the peripheral retina, the time 

 interval elapsing between successive stimulations be brief, a character- 

 istic phenomenon appears. Instead of sensations which correspond in 

 tone with the objective stimulus, or with such transitions as have been 

 described above, the observer will report phenomena which seem, at 

 first sight, to be of the most irregular and accidental character. The 

 nature of this change of sensation is evident from the following table. 

 The experimental conditions under which these results were obtained 

 were identical with those already described, excepting that the interval 

 between successive exposures was here reduced to one minute or less. 

 Each group of results in the table represents a series of stimulations of 

 the horizontal meridian of the nasal retina, applied at the degrees of 

 eccentricity indicated. The settings of the stimulus-lantern were made 

 in irregular order ; but in every case the same order has been preserved 

 in setting down the results. Here again we have chosen but a few of 

 the typical series from a large number of similar character. 



R. 85 Gray. R. 90 Gray. 



75 Yellowish. 80 Yellowish. 



65 Yellowish. 70 Yellow. 



55 Yellow. 60 Gray. 



45 Bluish. 50 Blue. 



35 Blue. 40 Bluish. 



75 Blue. Rest of five minutes in darkness. 



85 Bluish. 60 Yellow. 



50 Yellow. 



O. 80 Yellowish. O. 85 Gray. 



70 Yellow. 75 Yellowish. 



60 Yellow. 65 Yellow. 



50 Bluish. 55 Yellowish. 



40 Blue. 45 Blue. 



80 Bluish. 75 Blue. 



85 Bluish. 



Rest of five minutes in darkness. 



85 Gray. 



75 Yellowish. 



45 Yellow. 



