The Action Potential in Fibers of Slow Conduction in Spinal Roots and Somatic Nerves.

Abstract

The group of waves, alpha, beta, gamma and delta, hitherto described as constituting the conducted action potential of mixed somatic nerve 1 , 2 are confluent and are produced by groups of fibers conducting at rates ranging in round numbers, in the bullfrog, green frog (at room temperature) and dog (at body temperature), between 40 and 10, 35 and 8 and 80 and 30 m.p.s., respectively. Together they form what may be called the A elevation. When the record obtained from these nerves by the cathode ray oscillograph is continued through 200 to 300 σ, instead of stopping after 10-15σ as has been usual hitherto, and higher amplification, 100,000 instead of 8,000, is used, 2 additional and discrete elevations, which, like A, may be compound, appear in succession as the stimulation is raised to strengths far beyond those previously employed by us. The second, or elevation B travels at the rate of about 5 to 2 m.p.s. in mixed nerves of the bullfrog and green frog and 17 (20 in one case) to 11 m.p.s. in the dog, the rates in the contributing fibers ranging down to about 2 to 1 m.p.s. in the frog and to about 8 m.p.s in the dog. The third or C elevation is conducted at the rate of 0.7 to 0.5 in the frog and 1.5 to 0.8 m.p.s. in the dog, the rates in the slowest fibers ranging down to about 0.3 m.p.s. in the frog and to 0.5 m.p.s. in the dog. The 3 elevations, A, B and C, are propagated at such diverse rates that in less than 1 cm. of conduction they become quite clear one of the other, in this respect differing strikingly from the alpha-beta-gamma waves of A which are confluent at all distances of conduction.