34 COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 



the white-values and the color-values of his stimuli had been equated, 

 the coincidence of his values would doubtless have been even more com- 

 plete. Guillery explains his results in terms of the Hering theory. 



Tschermak* made an elaborate investigation in 1897-8, in which 

 he employed both spectral and pigment colors. His experiments estab- 

 lish the fact that the disappearance of color in indirect vision is condi- 

 tioned by numerous factors. His results may be summarized in the 

 statement that the capacity to perceive color in indirect vision is a func- 

 tion of the extent of retinal surface stimulated, of the color-tone, the 

 saturation and the brightnessf of the stimulus, and of the momentary 

 condition of adaptation of the visual organ. 



NOTE. Our manuscript was in the hands of the publishers when 

 Peters's recent paper appeared. (W. Peters. Die Farbenempfindung 

 der Netzhautperipherie bei Dunkeladaptation und konstanter subjectiver 

 Helligkeit, Archiv fur die Gesamte Psychologic, III, 4, 1904, 8.354-387.) 

 Our estimate of his method and results will be found in the Journal of 

 Philosophy, Psychology, and Scientific Methods, II, i, 1905, pp. 2off. 



To summarize the results of this voluminous literature, and to 

 present, in small compass, the conclusions which have been reached, is 

 not an easy task. It is, however, a task which must be undertaken if 

 one is to understand and appreciate the present status of the problem. 

 We shall attempt, then, to find at least some general tendencies running 

 through the literature, and to indicate, if only in a general way, the goal 

 toward which they seem to tend. 



One might be tempted, at first sight, to believe that there is an 

 utter absence of agreement in the findings of the various investigators, 

 and to feel that opinion is no less sharply divided as to what are the 

 facts of indirect vision, than as to how these facts are to be interpreted 

 and explained. But even in the midst of an undeniable confusion as to 

 particular details, one may readily see that there are certain facts of 

 observation upon which all investigators are agreed. And even the 

 most discordant data will, in many cases, cease to baffle and confound 

 us, if we but examine them in the light of the different conditions of 



*A. Tsohermak. Beobachtungen iiber die relativen Farbenblindheit in dn- 

 direotem Sehen, Pfliiger's Archiv fur die Gesamte Physiologic, LXXXIII, 1900, 



S. 559-591. 



fUnder brightness is included both absolute and relative luminosity of 

 stimulus, i. e., its own brightness and its brightness-contrast with its background. 



