THE NEED for discovering a nervous disorder as early as possible is obvious. The diagnostic method to be described here utilizes a peculiar visual phenomenon which makes possible recognition of minute unilateral delays in perception of visual impulses. It is expected that this method, which takes advantage of the high degree of sensitivity of visual reception, will promote recognition of the disturbed function of the optic nerve at an earlier state than is obtainable with the existing methods. Fully aware of. the incompleteness of my clinical investigations,1 which began in 1942 and were interrupted by the exigencies of the war, I present the method for the purpose of further study in competent institutions. THE PULFRICH EFFECT The basic phenomenon is easily observed with the following simple setup: Let a pendulum (some small dark object tied to a thread) swing in front of and parallel with a light vertical background,