Cutaneous innervation.

This is a review of historical facets of research in cutaneous neurohistology. The silver stains, used for some 150 years, led to the discovery of the neurone theory and to contemporary comparative studies. The cholinesterase methods, used since 1950, are the most convenient for general studies of nerves. The fluorescence technique of Falck (1962) is valuable for the study of adrenergic fibers. The electron microscope techniques used since 1950 have allowed the comprehensive description of myelinated and unmyelinated nerve fibers and of corpuscles. The most important unsettled questions pertain to the physiology of cutaneous nerves and precise definitions of cutaneous sensibility.