On the Trophic Impulse So-Called, Its Rate and Nature

Abstract

When the lateral-line nerve of the cat-fish is cut, not only the nerve but also the lateral-line sense-organs posterior to the cut degenerate; those anterior to the cut remain intact. The posterior organs regenerate on the regeneration of the nerve. These results, already published by Brocklebank, have been re-investigated and confirmed. Such activities fall under the head of trophic influences. In this instance they must spread from the central end of the nerve toward the periphery, a direction opposite to that pursued by the sensory nerve impulses. By measurement, it was found that the trophic influence as judged by degeneration passed over the lateral-line nerve at a rate of about 2 cm. per day. This very slow rate as compared with that of the nerve impulse, indicates that these two processes are totally unlike. The so-called trophic impulse is probably dependent upon materials percolating through the nerve fibers from the cell bodies toward the periphery. These materials in some way unknown are essential to the integrity of the lateral-line organs. The trophic relations thus outlined are probably not the result of specialized nerve fibers, the so-called trophic fibers, but are characteristic of all nerve fibers.