LETTERS in NATURE by Dartnall and Goodeve1 and by Wald2 have revived the question concerning the physiological significance of visual purple and visual yellow. Dartnall and Goodeve discuss the scotopic luminosity curve and compare it with the absorption curve for amphibian visual purple, determined by Lythgoe3. Attention may perhaps be directed to the fact that the retinal equivalent of the frog's luminosity curve has been measured by Granit and Munsterhjelm4 with the aid of the electrical response. In this work, luminosity was obtained in terms of the amount of potential in millivolts of the initial positive b-deflection of the electroretinogram in response to stimulation with an equal energy spectrum.
Dartnall and Goodeve, NATURE, 139, 409 (1937).
Wald, NATURE, 139, 587 (1937).
Lythgoe, J. Physiol., 89, 331 (1937).
Granit and Munsterhjelm, J. Physiol., 88, 436 (1937).
Chaffee, Bovie and Hampson, J. Amer. Opt. Soc., 7, 1 (1923).
Granit and Wrede, J. Physiol., 89, 239 (1937).
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GRANIT, R. Absorption Curve for Visual Purple and the Electrical Response of the Frog's Eye. Nature 140, 972 (1937). https://doi.org/10.1038/140972a0