The Philosophical Review/Volume 1/Summary: Ladd-Franklin - Eine neue Theorie der Lichtempfindungen
Though both the Young-Helmholtz theory of light- and color-vision and the hypothesis of Hering count many adherents,—the former among physiologists, the latter principally, perhaps, among pathologists,—the inadequateness of both to a full explanation of the phenomena has long been recognized in psychology. As early as 1874, Wundt (who, curiously enough, is not referred to in Mrs. Ladd-Franklin's paper, although Donders and Göller find mention) had propounded a periodicity-theory in place of the three- and four-component hypotheses. Mrs. Ladd-Franklin, regarding these latter as the only alternatives, prefers the former of them, on the ground of Konig's and Dieterici's results: in other respects the theory which she proposes most nearly resembles that of Bonders. Two kinds of "molecules" are assumed to exist in the photochemical substances of the retina: gray molecules, which alone occur in the totally color-blind retina, at the periphery of the normal retina, and (probably) in the eyes of many of the lower animals,—and the dissociation of which is the cause of the sensation of gray; and color-molecules, which have arisen by differentiation from these, in that the atoms of their external layer have become grouped in three directions at right angles to one another. The writer claims that her theory is superior to the older ones especially in two regards: firstly, as rendering intelligible the distribution of the retinal rods and cones; and secondly, as accounting for the fact that red-green and green-blue mixtures appear less saturated than the simple colors. The crucial objection to the hypothesis, as the author sees, is that yellow is for sensation as simple a color as red or green. Nor is the theory helped by the introduction of a conjectural retinal physiology. Finally, judgment must in any case be suspended until the writer has published her promised investigation of the assumptions underlying Hillebrand's alleged proof, that in color-mixtures which arouse the sensation of white the component color-processes cancel one another.