Hekrick, Color Vision. 275 



no difference whether one color impression was acting or a dozen were 

 cooperating to impress their mode as the dominant in the equihbrium. 

 The result in either case would be a unitary impression or feeling. 



But is it not true that all shades of green, for instance, are recog- 

 nized as phases of one color ? To a certain extent this is true. Differ- 

 ent kinds of green are all called green, though when placed side by 

 side they seem to differ greatly. But it is impossible for me to say 

 that one out of the many is a pure green and the others are mixtures. 

 It does not appear that there is a composition of simple sensations of 

 which one element (say in this series of green.s) remains constant and 

 serves to label all of these nuances "green," while a variable element 

 affords a means of identifying one as emerald green and another as 

 grass green, etc. In fact, it is possible to arrange a series of shades 

 which pass imperceptibly from green into blue, as would not be the 

 case if green and blue were fundamentally different sensations in any 

 other sense than are various sensations of green. Such fusion as there 

 is must be infra-conscious — a nervous process or, at least, a process be- 

 low the threshold of consciousness. 



Professor Calkins, in criticising the Helmholtz theory of color, 

 says "Yeilow looks to u.s simply yellow and does not in the least ap- 

 pear like a mixture of red and green nor like any other color mixture." 

 We would go farther and add that any color or shade whatever looks 

 like itself and by no means like a mixture of other colors. If various 

 shades of green, e. g., resemble each other more than they do some 

 other primary color this is a subjective fact by itself as is the very fact 

 that certain nervous processes give rise to the mode "green" rather 

 than some other mode of sensation (a fact wholly inexplicable like any 

 "genetic mode"). But, as a matter of experience, some shades classed 

 as green resemble some shades classed as blue more than they do the 

 extreme shades of green. The fact of such resemblance is not to be ex- 

 plained as the result of mixture but as the result of the power of a cer- 

 tain range of color-stimuli to awaken, concomitantly with their color 

 sensations, accessory activities and to call them into sympathetic vibra- 

 tion in the equilibrium. 



The basis of resemblance and difference perception is undoubtedly 

 cortical and is a function of the equilibrium resembling those elements 

 upon which we base judgments of position, etc., even though they are 

 not separately perceived. 



Now if we attempt a discussion of the nature of the analysis of 

 light into what are called primary colors we are at once struck by the 

 fact that light itself affords us no such analysis. A light wave is not a 



