DUALITY IN THE ELECTRICAL RESPONSE OF THE LATERAL EYE OF LIMULUS POLYPHEMUS

¹ Marine Biological Laboratory and Department of Physiology, University of Illinois

Retinal action potentials recorded from the excised lateral eyes of Limulus, using a short time constant amplifier coupling, show a dissociation into two discrete responses, an initial and a secondary phase, over part of the intensity range. Analysis of the data indicates that the single response present at low intensities of stimulation is the initial phase and that both phases are present only in response to higher intensities of illumination. This sequence of single and dual phases with increasing intensity of stimulation gives rise to the peculiar peak-time relation shown in Figure 3. Light adaptation causes a rapid disappearance of the initial phase and only a gradual disappearance of the second phase. The magnitude of the initial phase is much smaller than the magnitude of the second phase. These data suggest that the initial phase represents the response of highly sensitive receptors (eccentric retinula cells) that are outnumbered by less sensitive receptors which contribute to the second phase (the radial retinula cells) (Demoll, 1914). Procain hydrochloride administered to the excised eye results in a reduction in magnitude of phase 2, and little or no change in magnitude of phase 1.

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