THE STRUCTURAL IDENTITY OF THE PAIN SPOT IN HUMAN SKIN

Abstract

Areas of skin were removed to various depths surgically or chemically and the regeneration of sensory spots was followed by means of electrical and mechanical stimulation. Most superficial pain and touch endings are located within the dermis and not over .1 mm. below the epidermis. Barium sulphide treatment sufficient to remove epithelium kills nerve fibers deeper than this. Pain returns with regrowth of nerve twigs, in general one twig to each group of 1-3 follicles. An initial sensitive point later expands to restore the normal skin spot. When unit areas containing one fol-licular group and one pain twig are excised during regeneration, or when normal skin is removed surgically, each pain twig can be located by stimulation as a sensitive point. Other twigs containing touch fibers or innervating follicles can be similarly located but their stimulation gives only touch. Some pain twigs, however, contain touch fibers. It is concluded that each pain spot is innervated by several pain fibers, the more sensitive spots by a greater number; each such twig spreads out over a unit area with a central most sensitive point over the twig; higher sensitivity here than elsewhere is accounted for by the larger number of fibers whose endings can be stimulated at this point; a continuous subepithelial nerve net is formed by the overlap of pain and touch ramifications.