Mode of Action of Visual Purple


FOR the chemical theory of excitation of nerve cells, the following observations as to how the retinal rods are stimulated by the substance visual purple would seem to be of general interest. Their understanding requires knowledge of the fact that after a preceding period of adaptation to sunlight the size of the electrical response of the eye to a constant test light reproduces the curve of regeneration of visual purple (see, for example1,2,3). When the quantity of visual purple, obtainable from an eye after increasingly longer periods of dark adaptation, increases, the size of the electrical response (its b-wave) likewise increases owing—one would have thought—directly to the larger amount of cell stimulant available.

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  1. 1

    Tansley, J. Physiol., 71, 442 (1931).

  2. 2

    Charpentier, Acta Ophthalm. Kbh., Suppl. 9 (1936).

  3. 3

    Granit, "Processes of Adaptation in the Vertebrate Retina, etc." Documenta Ophthalmologica, 1, 1 (1938).

  4. 4

    Granit, Therman and Wrede, Skand. Arch. Physiol. (in the Press).

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GRANIT, R., HOLMBERG, T. & ZEWI, M. Mode of Action of Visual Purple. Nature 142, 397 (1938).

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