On the Sensory Nerve Distribution in the Mucous Membrane of the Cavum Oris and the Pars Nasalis Pharyngis of Cat in the Last Fetal Stage

Abstract

In a fetus of cat of the last stage, the tongue papillae are already in nearly full formation. The filiform papillae comprise small and large types, the former found in the peripheral parts of the tip of the dorsum linguae and the latter in the other parts, including the radix linguae.The small-sized filiform papillae have stocks growing out from the propria into the epithelium and protrude into the oral cavity with their horn-teeth. The large-sized filiform papillae have conspicuous furrows between them and well-developed stocks, but are lower in statue and lose their horn-teeth in the rear parts of the tongue.The development of the stocks of the small-sized filiform papillae being poor, the number of sensory fibres innervating them is very small, only the better-developed papillary stocks among them being provided with incoming sensory fibres, which end in unbranched and simple branched terminations. Their terminal fibres are usually fine and show little change in size in their courses before they end in sharp or blunt pints subepithelially or sometimes intraepithelially.The papillary stocks of the large-sized filiform papillae being better developed, sensory fibres as well as vegetative fibres are found always in them. Most of the sensory fibres end in subepithelial simple branched terminations, but their terminal fibres show frequent change in size and marked winding courses and end sharply or bluntly.The fungiform papillae are found not only in the peripheral but also the more central parts of the dorsum linguae too. The fungiform papillae found amidst the small filiform papillae are much smaller than those amidst the large filiform papillae. A fungiform papilla is always bounded off from the filiform papillae around it by a distinct circular furrow, and is covered on the top side by a non-cornified stratified flat epithelium containing taste-buds but thinner than that facing the furrow. In the basis of their stock, a nerve plexus is sometimes formed containing hemiganglion cells, but usually a mere thick nerve bundle runs up through the stock and spreads out subepithelially. This bundle contains thick sensory and thin vegetative fibres, the former usually ending in simple branched terminations, but more rarely in rather complex branched terminations originating in very thick fibres and having terminal fibres frequently changing in size and winding in their courses. Besides, intraepithelial and especially extra- and intragemmal fibres are in marked development. The vegetative fibres always end in terminal reticula spread out beneath the tastebuds and interestingly enough, in close relation with sensory terminations. The same may be said of the vegetative fibres in the vallate and the foliate papillae mentioned below.The vallate papillae are covered by a thin stratfied flat epithelium and many taste-buds are found in it on the sides facing the furrow as well as the oral cavity, and a smaller number of them are seen in the outer wall of the surrounding furrow, too. The foliate papillae are found in the rear lateral parts of the dorsum linguae. These have a furrow only on their medial side in adult cat, but in fetal cat, another furrow is found on their lateral side too. Taste-buds are present not only in the epithelium facing these furrows but also in that facing the oral cavity. The tastebuds in the wall of the medial furrow alone are found in adult cat too, but those in the other parts above seemingly degenrate away gradually after birth.In fetal cat, the vallate and the foliate papillae have already basal plexus containing REMARK's hemiganglion cells formed in their basis. The sensory fibres and the vegetative fibres emerging thence spread out fan-wise toward the epithelium. As in the fungiform papillae, their terminations comprise unbranched and simple branched subepithelial and intraepithelial or intra- and extragemmal terminations.