. Kirkes' handbook of physiology . Fig. 474.—Diagram to Illustrate the Stimulating Effects of the Three Primary Colors. (Young-Helmholtz theory.) 1 is the red; 2, green, and 3, violet, primary color sensations. The letteringindicates the colors of the spectrum. The diagram indicates by the height of the curve to whatextent the several primary sensations ef color are excited by vibrations of different wave lengths.(Helmholtz.) white-black substances. By the theory, when the red-green substance isstimulated by red or green light, respectively, the former produces destruc-tive or catabolic change
. Kirkes' handbook of physiology . Fig. 474.—Diagram to Illustrate the Stimulating Effects of the Three Primary Colors. (Young-Helmholtz theory.) 1 is the red; 2, green, and 3, violet, primary color sensations. The letteringindicates the colors of the spectrum. The diagram indicates by the height of the curve to whatextent the several primary sensations ef color are excited by vibrations of different wave lengths.(Helmholtz.) white-black substances. By the theory, when the red-green substance isstimulated by red or green light, respectively, the former produces destruc-tive or catabolic changes, the latter constructive or anabolic changes, in thesubstance. When red light falls upon the retina, it produces catabolism inthe red-green substance, which in turn develops a nerve impulse that arouses. Fig. 475.—Diagram to Illustrate the Reactions of the Three Photogenic Substances, accordingto Herings Theory. (Foster.) the sensation of red. When green light, on the other hand, stimulates theretina, it produces anabolism of the red-green substance and the sensation ofgreen. The same rule holds with the other two substances. It will benoticed that this theory is based on the complemental colors. (j(J4, THE SENSES When we apply the theories mentioned above to the phenomena of color-contrast and color-blindness, we find that each is defective in some the Young-Helmholtz theory it is difficult to understand the perceptionof the sensation black, for by the theory black could be perceived only asthe absence of all colors, and it is generally granted that there is a distinctblack sensation other than and different from mere darkness. This theoryexplains those cases of blindness to one color, as red-blindness, for Hering theory, on the other hand, gives us a rational
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