The object of this research was to obtain data on the physiologic properties of nerves from normal monkeys, first, for comparison with nerves from monkeys afflicted with poliomyelitis, and second, for comparison with the nerves from other normal species, on which a considerable amount of data is being accumulated. METHODS The animals employed were adult normal Macacus rhesus from stocks supplying poliomyelitis researches. Data were obtained by photographically recording the action potentials of freshly excised nerves, employing the cathode-ray oscillograph and a four-stage resistance-coupled amplifier, the whole having a sensitivity of 200 mm. per millivolt and no appreciable inertia. The nerves were removed under light ether anesthesia and when the data were not recorded immediately were kept in iced Ringer's solution, where they would remain approximately normal for from one to three hours at least. They were placed for experimentation in a water-jacketed thermostat at 37 C., mounted on Ringer-filled