Abstract
The human eye was stimulated by sinusoidal alternating currents of varying frequencies in order to study the relation between the threshold voltage and the frequency. The strength-frequency curve obtained in this way showed three minima at about 18, 37 and 53 c. p. s. These minima appeared most conspicuously under moderate light adaptation of the eye.
Similar results were obtained with constant current pulses of varying frequencies. In the above experiments, the stimulating current was increased or decreased slowly and steadily. When the eye was stimulated by sudden make of stimulating currents, the minima were flattened only to a slight degree. This finding suggests that the minima under considera-tion were produced by resonance, and the appearance of multiple minima in the strength-frequency curve indicates that there are as many excitable tissues with different time constants in the human retina.
