Innervation density of mechanoreceptive fibres supplying glabrous skin of the monkey's index finger.

Abstract

The innervation densities of mechanoreceptive fibers supplying the ridged glabrous skin of the middle and terminal phalanges of the monkey''s (M. nemestrina) index finger were estimated using a combination of histological and neurophysiological procedures. This estimate was based on a count of the total number of A.beta. myelinated fibers in the palmar digital nerve at the level of the proximal phalanx, on demonstrating that the majority of A.beta. fibers in the monkey''s palmar digital nerve are mechanoreceptive afferents, the estimation, based on a sample of 398 fibers, of the fraction of rapidly adapting, slowly adapting and Pacinian mechanoreceptive fibers in the palmar digital nerve and the estimation of the area of glabrous skin innervated by the palmar digital nerve. The estimated innervation density of the finger pad and the skin of the middle phalanx was 178 and 80/cm2 for rapidly adapting fibers, 134 and 46/cm2 for slowly adapting fibers and 13/cm2 Pacinian fibers of both phalanges, respectively.