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Charge transfer through the receptor membrane of the nonmyelinated ending of Pacinian corpuscles is markedly affected by temperature. The rate of rise and the amplitude of the generator potential in response to a constant mechanical stimulus increase with temperature coefficients of 2.5 and 2.0 respectively. The duration of the falling phase, presumably a purely passive component, and the rise time of the generator potential are but little affected by temperature. The following interpretation is offered: Mechanical stimulation causes the conductance of the receptor membrane to increase and ions to flow along their electrochemical gradients. An energy barrier of about 16,000 cal/mole limits the conductance change. The latter increases, thus, steeply with temperature, causing both the rate of rise and the intensity of the generator current to increase.The membrane of the adjacent Ranvier node behaves in a distinctly different manner. The amplitude of the nodal action potential is litt|e changed over a wide range of temperature, while the durations of its rising and failing phases increase markedly. The electrical threshold of the nodal membrane is rather constant between 40 and 12°C. Below 12°C the threshold rises, and the mechanically elicited generator current fails to meet the threshold requirements of the first node. Cold block of nerve impulse initiation then ensues, although the receptor membrane still continues to produce generator potentials in response to mechanical stimulation. I N T R O D U C T I O NMechanical stimulation of the receptor membrane of-Pacinian corpuscles causes transfer of charges. The amount of charges transferred increases with the area of membrane excited (Loewenstein, 1959(Loewenstein, , 1961, and with the electrical gradients across it (Loewenstein and Ishiko, 1960). A plausible mechanism of the charge transfer process is that the mechanical stimulus produces an increase in conductance of the receptor membrane, and that charges move along their gradients through the membrane. This paper deals with an aspect ~o5

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