The spatial distribution of electric responses to focal illumination of the carp's retina.

Potentials in response to microillumination were recorded with a 3 M KCl-filled microelectrode of about 1 μ in diameter in the illuminated and surrounding areas of the inverted preparation of the carp's isolated retina. 1. The shape of an electric response to a small spot of light less than 1mm. in diameter was almost rectangular, and its polarity was positive at the illuminated part, but negative in the surrounding area. The negative potential was detectable as far as 2mm. from the margin of the illuminated part. 2. Light adaptation of suitable intensity was favorable for the manifestation of negative potentials in the surrounding area, and this effect is to be ascribed to suppression of the effect of stray light by light adaptation. 3. The negative potential was suppressed at low temperatures below 8°C more strongly than the positive potential. 4. No negative potential was induced beyond a mechanical cut made closely to the margin of the illuminated area. 5. The positive potential at the illuminated locus was highest at the outer surface of the retina, while the negative one in the surrounding area was maximal in amplitude at an apparent depth of about 100 μ from the receptor side.