Kornmüller,1in recording the spontaneous electrical activity of the cerebral cortex in several mammals (rabbit, cat and ape), interpreted his findings as indicating that fields of the cerebral cortex known to differ in their cytoarchitectonic pattern differ likewise in the wave pattern obtained. The present report is concerned with the architectonic limits of the optically excitable cortex of the rabbit, i. e., the area of cortex in which a characteristic pattern of activity interrupts the spontaneous fluctuations following application of single stimuli to the contralateral optic nerve. With the animal under light ether anesthesia, the optic nerve, after removal of the eye, was stimulated directly by single maximal electrical shocks, each stimulus resulting in a single volley of impulses in parallel fibers passing over the pathway as nearly synchronously as possible. The pathway consists of the optic nerve and tract (most of which crosses in the rabbit chiasm), the