COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 73 



the complementary blue or yellow appears as a final stage. All of these 

 changes occur in the presence of the stimulus. 



(6) The stimulation of the peripheral retina is attended by char- 

 acteristic after-effects. These may be described as being rudimentary 

 after-images. They are analogous with after-images in that (a) they 

 possess a complementary character; but they differ from after-images 

 in that (b) they are (or at least were under our experimental condi- 

 tions) wholly latent and unconscious (or sub-liminal). Their presence 

 was felt, however, in the changed quality of the sensation aroused by 

 subsequent stimulation, (c) A prominent characteristic of these after- 

 effects is their persistent duration. They can be got rid of only by 

 resting the eye for a considerable period after each stimulation, (d) As 

 to their spatial attributes, our experiments justify only the general state- 

 ment that they seem to extend over a wider retinal area than did the 

 images which occasioned them. 



(7) There seems to be no doubt that Hellpach's zone of comple- 

 mentariness is an artifact, and that its discovery is wholly due to the 

 experimenter's failure to avoid retinal fatigue in his explorations. The 

 peripheral retina is readily fatigued, and the fatigue-effects here persist 

 with extraordinary tenacity. This characteristic is also present, though 

 in lesser degree, at every other part of the retinal surface. When a 

 color-stimulus which has already fatigued any region of the retina is 

 reapplied to the same or an adjacent region before the retina has fully 

 recovered from its previous stimulation, the resultant sensation tends 

 to appear either colorless or in a tone which is complementary to that 

 of the primary sensation aroused by the same stimulus at that point.* 

 This phenomenon has been abundantly demonstrated in this and in 

 numerous other investigations ; it is unquestionably the same phenome- 

 non which Hellpach reports. Hellpach is in error, however, in sup- 



*It is, of course, incorrect to say that these fatigue-products are comple- 

 mentary to the "objective Farbe" of the stimulus as seen in direct vision. (See 

 Hellpach, 1. c., S. 537.) Such a characterization is true only in case the stimuli 

 employed represent stable tones. In every case the tone of the " fatigue sen- 

 sation " aroused at a given region is complementary to the primary or " non- 

 fatigue " sensation aroused at that region. Thus a purple stimulus is attended by 

 green after-effects only at those regions where the purple of the stimulus is recog- 

 nized. Upon those regions where this stimulus appears yellow, subsequent stimuli 

 seem to be tinged with blue. This is in accord with Hellpach's finding that red, 

 orange, and yellow all appear bluish upon the " gegenfarbige Zone." Strangely 

 enough, he reports that green appeared yellow-reddish and purple appeared 

 yellow-greenish upon this outermost zone. This irregularity can be explained 

 only on the assumption that Hellpach's green and purple stimuli were more in- 

 tensive than the others. 



