The study of the reaction of the visual system to light stimuli of minimal duration has a meager background. For many years it has been known that the outlying borders or periphery of the retina reacted less to stimuli than the central or macular area. Indeed, this fact has caused to be instituted a distinct and separate branch of investigation known as perimetry. My aim in this dissertation is to determine the reaction of the peripheral portions of the normal retina to light stimuli of minimal duration. With such facts as could be determined concerning normal persons, it is hoped that for a further study deviations from these normal findings might give some clue as to the nature of changes in pathologic cases. Thus a group of medical students at Northwestern University, considered in average normal condition, was examined and special attention was given to the eyes. In none of