On the Microscopic Anatomy and the Sensory Nerve Supply of the Tongue in Flying-Squirrel

Abstract

The mucous membrane of the tongue of flyig-squirrel may be called rather rich in sensory nerve supply, but far lese rich than the same of man and other higher mammals studied hitherto. The foremost part of the dorsum linguae and the entire facies inferior linguae with poorly developed propria contain only very poor proprial plexus and consequently the number of sensory fibres cming from this plexus is very few. Only the fungiform papillae found sporadically in the foremost part of the dorsum linguae have often well-developed proprial plexus under them. The propria is well developed in the middle and the psoterior parts of the dorsum linguae and the radix linguae, permitting good development of the proprial plexus.The sensory supply to the filiform papillae is very poor in the foremost part but grows better in the parts more to the rear of the dorsum linguae and falls off a little again in the radix linguae. So, the sensory innervation of the papillae in these parts runs parallel with the size of the papillary stocks. Namely, the very ill-developed filiform papillae found in the foremost part are devoid of sensory fibres, except the few somewhat stouter papillae found in this part into which 1 or 2 sensory fibres run and end in unbranched terminal fibres therein. The considerably well-developed filiform papillae in the middle part of the dorsum linguae are always supplied with sensory fibres which end in simple and complex branched terminations; the terminal fibres of these often show very perceptible change in size and sometimes end after penetrating the epithelium very slightly. The filiform papillae with the largest stocks found in the hinder part of the dorsum linguae are the best provided with sensory fibres and their terminations among all the filiform papillae. These terminations include not a few uncapsulated simple glomerular terminations. The filiform papillae in the radix linguae are somewhat worse developed than those in the preceding part.Into a fungiform papilla, a rather thick nerve bundle composed of a few medium-sized sensory fibres and many fine vegetative fibres comes in and spreads out in the top part of the stock. The sensory fibres end in unbranched and simple branched terminations beneath the taste-budded epithelium, and only a very few of the terminal fibres in intra- or extra-gemmal fibres. The vegetative fibres end in terminal reticula as always.In the lateral margins of the rear part of the dorsum linguae of flying-squirrel are found formations taking place of the foliate papillae in the upper and lower walls of the longitudinal deep furrow located there. The propria of both the walls contains complex ground plexus sometimes containing a number of REMAK's hemiganglion cells. This plexus consists of numerous fine vegetative fibres and a fewer thick sensory fibres, of which the former end in well-developed terminal reticula beneath the taste-budded epithelium, while the latter form simple and complex subepithelial branched terminations with terminal fibres often enough of thick size and not rarely ending intra- or extra-gemmally.The vallate papillae on the tongue of this animal are very few but well developed and have very well-devloped ground plexus containing some REMAK's hemiganglion cells in their basis; these plexus containing numerous fine vegetive fibres and fewer sensory fibres run into the papillary stocks and spread out the nerve fibres toward the taste-budded epithelium, beneath which the terminations are formed, just in the manner as in the taste-budded furrows. The sensory terminal fibres here too often form intra- and extragemmal fibres. Well-formed branched sensory terminations composed of thick terminal fibres are found in a rather large number in the taste-budless epithelium in the basis and the encircling wall of the vallate papillae and the terminal fibres from these terminations frequently end inside the epithelium.