Unmyelinated nerve fibers associated with Meissner's corpuscle in the green monkey (Cercopithecus aethiops L.)

The ultrastructure and organization of free nerve fibers occurring in dermal papillae containing Meissner's corpuscles were studied in the fingertips of the Green Monkey (Cercopithecus aethiops L.). The course of the thin unmyelinated fibers leads in the vicinity of Meissner's corpuscles in the connective tissue of its sheaths, between the epidermis and the peripheral fibroblast layer; they never come into contact with the nervous component of the receptor. Consequently, neither a "pericorpuscular reticulum" nor an "apparatus of Timofeew" is formed. The presence of thin axons containing dense-cored vesicles is evident, but they are not autonomous fibers, as indicated by the negative results of the Falck-Hillarp test for catecholamines. The nerve fibers occasionally seem to bear a close resemblance to the "open" and "plain" endings described by other authors in papillae devoid of corpuscles. Despite failure for close mutual contact to be established between the Meissner's corpuscle and the unmyelinated fibers ramifying in the connective tissue surrounding it, the hypothesis that the two may cooperate to form a "multimodal sensory package" is not without interest.