A number of reports in the literature1-14 have provided evidence indicating the existence of central nervous system control over the electrical activity of the retina, and some suggest4,5,6,8,10 quite strongly that the optic nerve conveys inhibitory influences from an hypothetical functional center. This study attempts to further elucidate the details of this interrelationship between the eye and the central nervous system. Methods A group of 40 adult cats were used in this study. Tracheal cannulae were introduced under ether anesthesia, and the femoral veins were cannulated for the administration of pentobarbital or succinylcholine chloride (Anectine). Artificial respiration and continuous intravenous drip of saline and dextrose maintained the preparation for 10 to 12 hours without appreciable signs of deterioration. Pupils were maximally dilated with phenylephrine hydrochloride (Neo-Synephrine) and cyclopentolate (Cyclogyl) to eliminate variation in pupil size as a source of error. The animal was placed in a prone position