It has been known that the tactile receptor in the epidermis is represented by a complex composed of a specialized receptor cell, called Merkel cell or Tastzellen, and its related axon since its discovery by MERKEL (1875). Several papers (CAUNA 1962, MUNGER 1965, MUSTAKALLIO and KIISTALA 1997 and a review (WINKELMANN 1967) have referred to the fine structure of the Merkel cell-axon complex in the mammalian skin as revealed by electron microscopy.Each report, however, was based upon only a few electron micrographs, since the Merkel cells occur rather infrequently in sections of the epidermis as known by the statement of MUSTAKALLIO and KIISTALA (1967) that it was encountered only once during the electron microscopic examination of 20 biopsy specimens from the adult human epidermis. We obtained many electron micrographs from more than eighteen different Merkel cells of three different species, one of which contained two strains, one was albino and the other was pigmented.Therefore, we can compare the fine structures of these specialized sensory epidermal cells between species, between different regions of the skin and between pigmented and non-pigmented animals.The probable mechanism of formation and release of specific granules of these cells which has been meagerly referred to in the previous papers will also be treated with in this report. Materials and MethodsThe sole skin from albino (ddN) and black (C57BL) mice, the pigmented snout skin of the dog and the axillary skin of a 7-month human fetus were used. The last specimen was taken from the product of legal abortion. Small pieces of skin were fixed in a vial containing ice-cold fixative consisting of 1% osmium tetroxide, veronal acetate buffer adjusted at pH7.4 and 4.5% sucrose for about 2hrs. After finishing the fixation the specimens were dehydrated through a series of increasing concentrations of ethanol and then embedded in Epon 812. Ultrathin sections were cut with glass knives on either an MT-1 or an MT-2 type of Porter-Blum microsome. Sections were stained with uranyl acetate followed by lead hydroxide and examined with a Hitachi HU-11 D electron microscope.

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