“…Schwann cells were never seen in contact with denervated synaptic folds (n = 14) although none of the muscles were examined at times shorter than 5 weeks after denervation, a considerable time after the Schwann cells have previously been reported to migrate from above the folds in mammals (Bauer, Blumberg & Zacks, 1962;Nickel & Waser, 1968;Miledi & Slater, 1968;LUillman-Rauch, 1971 (Li, Shy & Wells, 1957;Thesleff, 1963). Bursts of action potential firing sometimes occurred coincident with insertion of the micro-electrode, but more frequently action potentials were generated at regular intervals (frequency range 05-20 Hz in different cells), the activity resembling that recorded from pace-maker tissue in the heart (Weidmann, 1956).…”