1 7 8 RESPONSE IN THE LIVING AND NON-LIVING 



retina. The recurrent after-image is very distinct at 

 the beginning and becomes fainter at each repetition ; 

 a time comes when it is difficult to tell whether the 

 image seen is the objective after-effect due to strain 

 or merely an effect of ' memory.' In fact there is no 

 line of demarcation between the two, one simply merges 

 into the other. That this 'memory' image is due 

 to objective strain is rendered evident by its recur- 

 rence. 



In connection with this it is interesting to note that 

 some of the undoubted phenomena of memory are also 

 recurrent. ' Certain sensations for which there is no 

 corresponding process outside the body are generally 

 grouped for convenience under this term [memory]. 

 If .the eyes be closed and a picture be called to 

 memory, it will be found that the picture cannot be 

 held, but will repeatedly disappear and appear. ' 1 



The visual impressions and their recurrence often 

 persist for a very long time. It usually happens that 

 owing to weariness the recurrent images disappear ; 

 but in some instances, long after this disappearance, 

 they will spontaneously reappear at most unexpected 

 moments. In one instance the recurrence was observed 

 in a dream, about three weeks after the original im- 

 pression was made. In connection with this, the revival 

 of images, on closing the eyes at night, that have been 

 seen during the day, is extremely interesting. 



Unconscious visual impression. While repeating 

 certain experiments on recurrent vision, the above 

 phenomenon became prominent in an unexpected 



1 E. W. Scripture, The New Psychology, p. 101. 



