Observations on the retinal action potential with especial reference to the response to intermittent stimulation

IN the publications of the early workers on retinal action currents, observations on the response to intermittent light are often reported. The first to undertake such experiments were, we believe, Kiihne and Steiner [1880], who produced intermittent light by rhythmically compressing the rubber tube leading to their gas flame. But, apart from the finding that with this mode of stimulation the response also became rhythmic below a certain frequency of alternation, no really significant contributions were made to the problem until Piper in 1911 investigated the reactions of various types of vertebrate retinae to an intermittent stimulus of given strength. He observed several interesting facts which, as occasion arises, will be referred to below in connection with our own observations. Some general conclusions based on Piper's work still summarize the state of knowledge. The retinal response to intermittent light consists of undulations during the slow phase of the retinal action potential (c-wave), which disappear above a certain frequency of stimulation. This critical frequency is low in eyes containing mainly rods (cat), and very much higher in eyes in which cones predominate (pigeon). Where the retinal action current shows a well-developed initial negative a-wave and a marked off-effect (e.g. frog), these two appear to be among the factors determining the troughs and crests of the waves. Some observations of a similar character on the eyes of fishes were made by Day [1915] in Piper's laboratory. Since that time the retinal reaction to intermittent light has hardly been studied at all by direct methods. Renqvist [1924] noted that