COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 3! 



not give co-extensive zones, nor did his blue and yellow stimuli. Kirsch- 

 mann sees in these results an argument against the theories of Helm- 

 holtz and of Hering, but he fails to find an explanation for the phe- 

 nomena which he reports.* 



Abneyf performed a great many experiments in which spectral 



colors were exposed in different brightnesses and at different visual 

 angles. Employing as stimuli, red (670.5 /f/w), yellow (589.2 /*//), 

 green (508.5 jWyu), and blue (460.3 /*/*), whose relative brightnesses 

 were .3 : 4.5 : 2.1 : .4, he found blue to have the widest zone, yellow and 

 red lesser zones, and green the least of all. With complementary pairs 

 of stimuli, of widely different brightness saturation not stated he 

 found the green (500 ////) and blue (460 jujn) zones to be approxi- 

 mately coincident, that of red (650 ///*) to be narrowest, and that of 

 yellow-green (561 ///*) to be widest of all. In yet another experiment 

 he employed red, yellow, green, and blue light in nine different intensi- 

 ties each stimulus being half as bright as its predecessor. He found 

 that decrease of brightness invariably decreases the extension of the 

 color zone, and moreover each halving of the brightness contracts the 

 zone by an approximately equal (absolute) amount. So, too, an equal 

 increase of area of stimulus invariably increases the extension of the 

 zone by an approximately equal amount, until the stimulus subtends a 

 visual angle of 5 or more. He sees no reason why the limits of all 

 color zones could not be made to coincide by an appropriate choice of 

 luminosity and area of stimulus. 



DrottJ worked in daylight illumination with red, green, and blue 

 papers. His stimuli were presented in the form of squares which ranged 

 in size from 2 sq. mm. to 4 sq. cm. No determination was made of the 

 color tones employed, nor of their relative brightnesses and saturations. 

 His results indicate that with well-saturated stimuli, blue is perceived 

 at greatest distance from the fovea and red at least distance, while with 



*It is to be noted that Kirschmann' s stimuli were equated neither in white- 

 value, nor in color-value. The results of his determinations of the different 

 color-zones are for that reason wholly incomparable with each other. Nor did 

 Kirschmann make any attempt to employ stable icolor stimuli. Even in his 

 " experimentum crucis" (S. 598), where he proposes to test the validity of 

 Hering's interpretation of the results of Hess, Kirschmann fails to fulfill any one 

 of the three conditions demanded by the experiment. It was, of course, in- 

 evitable that such a procedure should yield wholly negative results. 



t W. de W. Abney. The Sensitiveness of the Eye to Light and Color, Nature, 

 XLVII, 1893, pp. 538-542; The Sensitiveness of the Retina to Light and Color, 

 Phil. Trans., igoA., 1897, pp. 153-193; The Color Sensations in Terms of Lumi- 

 nosity, Phil. Trans., 193, 1900, pp. 259-289. 



JAnton Drott. Die Aussengrenzen des Gesichtsfeldes fur weisse und farbige 

 Objecte beim normalen Auge, Inaug. Diss., Breslau, 1894, S. 1-32. 



