On the Sensory Innervation of the Palm and the Sole of Formosan Macaque

Abstract

The cristae intermediae go much deeper into the corium than the cristae limitantes in the skin of the palm and the sole of Formosan macaque. The collagenous fibres of the reticular layer of the corium not only stretch into the interior of the dermal papillae, but also frequently directly cover the tip parts of the cristae limitantes. The papillary layer is found conspicuosly around the cristae intermediae and in the upper parts of the dermal papillae. The sweat glands are sporadically found in the subcutis. No arterio-venous anastomoses were found in my monkey specimens.No primary or subcorial and secondary or subpapillary plexuses, as observed in the human palm and sole, were found in the skin of the same parts of Formosan macaque, either. The nerves proper to the hairless skin of these parts and comprising both vegetative fibres and sensory fibres send off the vegetative fibres to the sweat glands before ascending through the reticular layer alongside of the blood vessels and the sweat gland ducts and then entering the papillary layer covering the cristae intermediae, run up sometimes to the ridges of the cristae but mostly into the upper parts of the dermal papillae.As sensory terminations, PACINIan bodies were found in the subcutis, MEISSNER's tactile bodies, non-capsulated glomerular terminations and branched terminations in the dermal papillae and specific branched terminations around the ridges of the cristae intermediae. Intraepidermal fibres originated in the branched terminations in the tip of some dermal papillae were discovered, but their number was much too small for regarding them as anything more than quite exceptional formations, as those found in the human palm and sole (WADA and AIBA). All the above sensory terminations are considerably simpler in construction than those found in the human counterparts.The branched terminations generally consist in simple-typed ones having only 2 or 3 branch fibres, but somewhat more complex ones are not absent. Most of these are formed in the dermal papillae devoid of MEISSNER's tactile bodies, but are more rarely found together with such bodies in the same papillae. Their terminal fibres often show change in size and sometimes accompany specific nuclei. Besides, peculiar branched or unbranched terminations having very short terminal fibres forming multiform fibrillar expansions or end-plates were found especially in the small papillae.Non-capsulated simple glomerular terminations are found only in a small number. The capsulated MEISSNER's tactile bodies comprise two standard types of different arrangement of the nerve elements in their oval inner bulbs. Most of the tactile bodies found in my specimens could be classed as belonging to one of the modifications of these standard types which consisted of the Type I, generally called the spiral, consisting in tactile bodies with their nerve fibres running parallel or spirally to the skin surface, and of the Type II, consisting of tactile bodies with fibres taking plexus-like or glomerular arrangement, thus to be named the plexu-stype or glomerular bodies. 1 or 2 sensory fibres are usually running into a tactile body, generally from the base side but sometimes from the lateral sides of the body and their terminal parts and their terminal fibres in the inner bulb undergo perceptible change in size.Of modifications of these standard types, mixed-type bodies occupy the overwhelming majority, but besides these, bodies with multifarious neurofibrillar expansions or end-plates, bodies sending out extracapsular fibres, certainly poorer in development than those in man, from their distal ends, bodies in which the spiral or parallel fibres as in Type I are turned into neurofibrillar net-works spreading one over another and many such modifications are also observable. It is of interest that very small-sized tactile bodies often were found in my monkey specimens.