The effects of injury on mammalian nerve fibres

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Abstract
Medium-sized nerves of cats and rabbits were isolated and set up in a warm, moist atmosphere. The electrical activity was recorded with a valve amplifier and a Matthews oscillograph (as described by Adrian and Umrath, 1929), and permanent records made with fast- and slow-speed cameras. The nerves give rise to persistent, rapid fluctuations of potential due to persistent discharge in some of the fibers of impulses of 3 types: (1) a continuous succession of impulses at a high frequency rarely less than 150 a second; (2) an irregular succession at a lower frequency; (3) a grouped discharge, each group consisting of several impulses closely spaced, the groups recurring at a frequency of 5-20 a second. The time relation shows that the nerve fiber is responding rhythmically to an excitation which outlasts the refractory period of the fiber. Discharges of the continuous type from several fibers may become synchronized, probably due to the stimulating effect of the action currents in one fiber on its neighbor. The persistent discharges start from the injured ends of nerve fibers where the depolarization acts as a stimulus to the intact part of the fiber. The effect is increased when the fiber is surrounded by dense structures like a thick nerve sheath or brought into an ab-normal condition by irrigation. The smaller sensory fibers, particularly those distributed to blood vessels and fascia, are probably those that react in this way. The relation of these discharges to pain is discussed, and the resemblance between them and the discharge of sense organs noted.

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