To investigate the excitability characteristics of the fiber components which mediate pain sensation and to study the electrical properties of the cell membranes of the neurons which have synaptic connections with the pain fibers. Special emphasis was made in reference to the response thresholds, conduction velocities and magnitudes of the various fiber components in the peripheral nerve and to the conductance and capacitance of the cell membrane of the neurons, which have synaptic connections with the pain fiber components, in response to various analgesic agents including morphine, beta-endorphin, etc.