Propagation Velocity and Total Reflection of Spreading Induction in the Light-Adapted Human Retina

Abstract

A process called “spreading induction” is started at the margin of a retinal image and propagated into the surrounding retinal areas. Thus a field of retinal induction is established around a retinal image. 1. The velocity of propagation was determined by measuring the latencies of the propagating process at various distances from the margin of a retinal image, and it was shown that the velocity depends greatly on the adaptation state of the retina, but only little on the intensity and hue of the light stimulus. 2. The value of velocity was 1.7mm. per sec. in the dark-adapted retina and 42mm. per sec. in the retina adapted to an illumination stronger than 1 lux. 3. When spreading induction comes across a white retinal image, it can totally be reflected at the margin of the retinal image. The critical angle of incidence for total reflection was determined, and on the basis of the law of refraction the velocity of spreading induction in the light-adapted part, the retinal image, was computed from the critical angle determined experimentally and the known velocity in the dark-adapted retina. The so computed values were found to agree satisfactorily with those determined by the direct method.