Interaction of slow potentials of the retina evoked by photic and electric stimuli.

Responses of inverted carp's retinae to direct electric stimulation were investigated with special reference to the effects of photic stimuli. 1. The response to an electric pulse (response E) increased in amplitude under background illumination of an optimal intensity, and was suppressed by strong illumination. 2. Interaction between response E and response to light (response L) was investigated. The response E was suppressed when superimposed on a positive-going response L at the site of illumination, but facilitated when superimposed on a negative-going response L recorded in the surrounding field of an illuminated locus. 3. Electrotonus giving rise to a potential variation of the same order as the response L did not cause any appreciable effect upon the response E. 4. When a mechanical cut was made between the stimulating electrode and the recording one, no response E was obtained beyond the cut. 5. As the distance between the stimulating and recording electrodes increased, the magnitude of response E decreased, and the peak-latency was prolonged. The relation between conduction distances and peaklatencies was linear. The conduction velocity obtained from this relation was 115mm./sec. on an average. This value coincided with the conduction velocity of the negative-going response L in the surrounding field.