COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 33 



Guillery* attacked the problem by an unusual method. He built 

 up the four stable colors upon a color-mixer, and introduced into his 

 observation-tube an adjustable diaphragm which enabled him to vary 

 the area of his stimulus at will. His aim was to determine the liminal 

 extent of colored surface which constitutes an adequate stimulus for 

 different regions of the retina, i. e., to determine for different parts of 

 the retina the minimal area of retinal image in which each of the four 

 colors can be recognized. His stimuli were not of uniform white-value 

 and color-value. 



The accompanying table shows the relative areas of the " liminal 

 images," which Guillery calculated from the settings of his diaphragm. 



A survey of these results shows that at every retinal region investi- 

 gated by Guillery, the sensitivity to red is approximately equal to the 

 sensitivity to green; while every retinal region also possesses an ap- 

 proximately equal sensitivity to yellow and to blue. In short, Guillery, 

 by a wholly different method, has, to some extent at least, confirmed the 

 results of Bull, Hess, and Hegg. The author himself remarks that if 



. Guillery. Vergleichende Untersucihungen iiber Raum-, Licht- und Far- 

 bensinn in Zentrum und Peripherie der Netzhaut, Zeitschrift fur Psychologic 

 und Physiologic der Sinnesorgane, XII, 1896, S. 243-313. 



