Abstract
The retinas and optic nerves of late juvenile and adult Rhesus monkeys that had survived transient, total arrest of systemic circulation were normal when examined with the light microscope. The period of circulatory arrest ranged from 12 to 30 minutes and the subsequent survivals ranged from four hours to one year. The optic nerve and retina thus seem to share with the rest of the brain a surprising degree of resistance to damage from circulatory arrest.