Abstract
Electro-nystagmographic investigations of optokinetic nystagmus under a variety of test conditions have made possible the identification of two separate and distinct mechanisms, one involving peripheral vision and the other foveal vision. Certain striking differences are apparent in the characteristics of these mechanisms which throw new light upon the neurological mechanism of optokinetic nystagmus in man and at the same time resolve many of the conflicting opinions which appear in the literature upon the subject.