Abstract
A group of neonatal chicks (subject) was kept in complete darkness before and after hatching, whereas another group (control) was raised under normal light conditions. The electric resistance and standing potential across the eyeball were measured between the cornea and occipital area on the 3-5 day after hatching. Under dark adaptation, the resistance of the subject group was much higher than that of the control. The standing potential of the subject group showed a large negativity of 4-15 mV on the cornea side, whereas that of the control group showed a slight positivity of 0.1-1.5 mV. The resistance and standing potential of the control eyeballs showed only a slight change during the light adaptation, whereas those of the subject group markedly decreased during the initial light adaptation. Ultimately, they became the same as the control group. These observed changes were irreversible, suggesting a certain structural change in the retina produced by the initial exposure to light. The results were discussed in relation to the morphological changes in photoreceptors observed after the initial exposure to light.
