Abstract
It is customary to consider the nerve axon as a cylinder with a porous surface through which pass ions of positive sign. The ions of the opposite sign remain on the inner side of the surface and this process of diffusion is said to continue until equilibrium is reached. The result is a cylindrical double layer of charges separated by a semipermeable membrane. Stimulation is viewed as a breakdown of this equilibrium state with a resultant shuffling of the charges at the point where the stimulus is applied. This state of ionic chaos moves down the axone as a zone of depolarization and constitutes the nerve impulse. Nerves may be stimulated by mechanical pressure, by heat, by various acids, and by electric current.
The setup used involved a pair of condenser plates 9 1/2 x 4 inches separated by a distance of 7 inches. A potential difference of approximately 10,000 volts was established between these plates at a frequency of 60 cycles. A preparation consisting of the sciatic nerve and the gastrocnemius muscle of the frog was employed. The preparation was extended on a carefully cleaned glass slide and placed between the plates of the condenser.
Under these conditions it was possible to rotate the glass slide carrying the preparation to form any desired angle with the electrical lines of force between the condenser plates. Beginning at 90 degrees, the slide was rotated alternately to one side and the other of this line by increments of 5 degrees. The results indicated that the effectiveness of stimulation varied as some direct function of the longitudinal component along the nerve axis. Beginning at 70 and 110 degrees, the intensity of contraction increased until at the maximum it became tetanic.
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