152 



COLOR-BLINDNESS IN ITS RELATION TO 



to their chromatic sense is to them, owing to its intensity, a more evi- 

 dent representative of that color than violet." 



This description of the manner in which the red-blind forms a con- 

 ception of the different kinds of light of the spectrum is assuredly a 

 conclusion logically deduced from the theory, but it accords so well, at 

 the same time, with the experience acquired in examining the color- 

 blind, that this might perfectly serve to support and corroborate the 

 theory. We will simply add a point for our esi^ecially practical purpose, 

 or rather emphasize one point of this theory. In fact, it is clear that a 

 red and green light especially excite one and the same element in the 

 red-blind. A ray red and green, or an object red and green, to the nor- 

 mal sense, must seem fundamentally to the red-blind to be the same color, 

 and if, in especial cases, he knows how to discriminate, his judgment 

 is simply guided by the intensity of the light. The intensity of light 

 is much more feeble, as shown by fig. 2, in red than in green. If then 

 a red-blind individual finds that a red and green tint are exactly alike, 

 it is necessary that the green be to the normal eye much less intense 

 than the red. This is distinctly shown by the vertical dotted lines 

 between R. and O., and also between Y. and G., in fig. 2, and this is 

 entirely confirmed by experience. 



2. Green-hlindness derives its origin, according to the theory, from the 

 absence or paralysis of the perceptive elements of green. The green- 

 blind has therefore but two fundamental colors, that is — still closely 

 adhering to the theory — red and violet (blue according to Maxwell). 

 The spectrum for green-blindness should be, according to the theory, 

 constructed in the following manner: 



Fig. 3. 



The spectral red, which strongly excites the perceptive organs of red, 

 and but very faintly those of violet, must therefore appear to the green- 

 blind as an extremely "saturated" red, but of a light somewhat less in- 

 tense than the normal red, which is comparatively more yellowish, as 

 green forms a part of it. The spectral orangeis again a very " saturated " 

 red, but much more luminous. Yellow is undoubtedly a more intensely 

 luminous red than the spectral red, but, on the other hand, more whit- 

 ish, because a sensible portion of the other primitive color enters into it. 



Green, with its shades inclining to yellow and blue, ought, correctly 

 speaking, to be a "saturated" purple and with a mean intensity of 



