An isolated nerve fibre, as it recovers from the condition of absolute refractoriness which follows activity, is known under suitable conditions to pass through 3 successive phases, relative refractoriness, supernormality, and subnormality.1, 2, 3 We have attempted to determine the course of recovery of nerve fibres in as nearly as possible physiological conditions, i. e., those conditions existing in the body of a healthy, intact animal. Etherized or decorticated rabbits were used, and induction shocks were applied either to the oculomotor nerve in situ,4 or to the sciatic nerve at the level of the trochanter major of the femur. The greatest care was taken to prevent hemorrhage, tissue injury or temperature change. Responses were recorded by means of a cathode ray oscillograph from the internal rectus muscle, the nerve to the inferior oblique muscle, the tibialis or gastrocnemius muscle or the deep peroneal nerve, according to the nerve stimulated. Thirty experiments were performed.The recovery curves ob...