32 COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 



poorly saturated stimuli the relative distances of the red and the green 

 are reversed. The limits of the zones vary with changes in area of 

 stimulus. 



Luckey* made a comparative study of the retinal extension of color 

 sensitivity in individuals who differed in age, sex, and training in color 

 discrimination. His apparatus consisted of a series of non-equated 

 colored papers, a perimeter, and a campimeter. He found the relative 

 extension of the zones to be (in descending order), blue, yellow, orange, 

 red, green, and violet. The zones extended farthest out on the upper 

 nasal region of the retina. Yellow and blue did not change in tone in 

 indirect vision ; all other colors appeared yellow (thus, green, red, and 

 orange stimuli) or blue (violet stimulus) before assuming their own 

 tones. Children have narrower zones than adults ; there is no variation 

 correlate with difference of sex, and little or no increase of zonal exten- 

 sion as a result of previous training in color discrimination. 



Hellpach-|- explored the dark-adapted retina with stimuli of ap- 

 proximately spectral purity. He devised a new form of perimeter, 

 which consisted essentially of an arrangement by means of which a 

 moveable stimulus-lantern could be exposed at any part of the visual 

 field. He employed red, orange, yellow, green, blue, violet, and purple 

 stimuli, which he built up by inserting appropriate combinations of 

 colored gelatines in the forward part of his lantern. These stimuli were 

 equated neither in white-value nor in color-value. His results are 

 characterized by two novel features ; his yellow stimulus arouses the 

 sensation of yellow upon no part of the peripheral retina, and all of his 

 stimuli tend to appear in their complementary tones at the extreme 

 periphery. Hellpach is convinced of the existence of four concentric 

 zones upon the retina: (i) a central zone upon which all stimuli ap- 

 pear in their true colors; (2) a paracentral zone where certain stimuli 

 appear in adjacent or transitional zones, e. g., violet appears blue upon 

 this region; (3) a more peripheral zone where all stimuli appear color- 

 less, and (4) an outermost zone where they appear in tones which are 

 complementary to their true colors, e. g., violet here appears yellowish. 

 His stimuli gave non-coincident zones of red and green, and of blue 

 and yellow. Hellpach believes that his investigation overthrows the 

 Young-Helmholtz and the Hering theories, but he feels it is yet too 

 early to attempt to replace them by a more satisfactory conception. 



*G. W. A. Luckey. Comparative Observations on the Indirect Color Range 

 of Children, Adults and Adults Trained in Color, American Journal of Psy- 

 chology, VI, 4, 1895, pp. 489-504- 



fW. Hellpach. Die Farbenwahrnehmung im indirecten Sehen, Phil. Studien, 

 XV, 1900, S. 524-S54- 



