402 PROCEEDINGS OP THE AMERICAN ACADEMY 



XXVIII. 

 COLOR-PERCEPTION. 



By G. Stanley Hall. 



Presented March 14, 1878. 



The finest distinctions which the ear can make — whether in detect- 

 ing differences as small as one sixty-fourth of a whole note, or between 

 harmonic upper partial tones — are, at first, purely mechanical pro- 

 cesses of the terminal apparatus of the auditory nerve. Only after 

 this process is complete, does the neural process of the extremely spe- 

 cialized fibres, which ends in the sensation of tone, begui. The physi- 

 cist can follow the sound waves as they are conducted through the 

 outer media of the ear, as their amplitude is diminished and their force 

 increased ; can calculate the amount of sympathetic vibration which 

 v?ill be caused in each part of the organism, as it passes ; and at last 

 determine the formulae by which it is analyzed into pendular vibrations, 

 by the organs of Corti or the fibres of the basilar membrane : thus 

 tracing it to the very verge of consciousness itself. 



In turning to the perception of color, we find that, if we take into 

 account the analogies suggested by the undulatory theory, and the 

 greater mniuteness of the waves of the light-ether, the eye — so far 

 as explored — responds to external stimulation with far less special 

 mechanical adaptation than the ear. Masses of white light are thrown 

 upon the retina, the focal distance of the various colors of which it is 

 composed differing by twice the whole retinal diameter and six times 

 the length of the longest rods, — every outline surrounded by disper- 

 sive and diffractive fringes, of ten times the diameter of the base of 

 one cone ; and here, with a vaguely defined, and to a great extent un- 

 verified, suggestion of three species of percipient elements, it is left. 



If this were really all, and neural action had to collect the material 

 of visual sensation in this form, and the mind, reacting upon such ag- 

 gregate stimuli, were able to project the whole visible universe of color, 

 — while we might understand why sight should have been the favorite 



