On the Nerve Supply of the Dorsum Linguae and the Facies Inferior Linguae in Newborn Dog

Abstract

The filiform papillae in the dorsum linguae of newborn dog are small-sized and of short cylindrical form; they are still in a low stage of development and consequently the number of the sensory fibres coming into their stocks is also very small. These fibres form undranched and simple branched terminations beneath the epithelium. The stem fibres are usually medium-sized, but sometimes thick stem fibres are also present and send out terminal fibres which show conspicuous change in size and some windings in their courses. The above findings are not much different from what has been reported on the same papillae of the adult dog. Neither intraepithelial fibres nor corpuscular terminations have been found in the filiform papillae.The fungiform papillae were much larger than the filiform papillae and their epithelium often contains taste-buds. In most of these papillae, a single nerve bundle runs through the basis into the stock and sends out nerve fibres radially toward the epithelium. The nerve fibres consist of fine vegetative and thick sensory fibres, of which the former end in STOHR's terminal reticula, but the latter end in unbranched and simple branched terminations beneath the epithelium. These sensory terminations are somewhat more complex than those in the filiform papillae above. The fungiform papillae contain some intraepithelial fibres of simplest unbranched type, but bifurcated intraepithelial terminations are not rare either. The sensory nerve supply to the taste-buds in these papillae is very poor indeed, some of the taste-buds being utterly devoid of any sensory fibre. No corpuscular termination was found in these papillae either.The foliate papillae on the tongue of the newborn dog were rather typically formed and taste-buds were abundant in the epithelium not only on the sides of the surrounding furrow but also on the side facing directly the oral cavity.The circumvallate papillae are small both in size and in number. Taste-buds are contained in the epithelium facing the oral cavity and in a smaller and variable number in the epithelium lining the sides of the surrounding furrow. The epithelium of the oral-cavity side was not yet found anywhere depressed, as observed in such papillae of the adult dog.Basal plexus containing REMAK's hemiganglion cells is formed in the basis of the foliate and the circumvallate papillae. This plexus consists of a larger number of fine vegetative fibres and somewhat fewer thick sensory fibres. The former end in very well-developed terminal reticula in the papillary stocks, while the latter fibres, much more numerous than in the fungiform papillae, spread out radially toward the epithelium and end beneath it. The sensory terminations are mostly of simple branched type, complex ones being as yet unformed. These sensory terminations come into very intimate relation with the vegetative fibres and terminal reticula. They are most often formed just beneath the taste-buds and their terminal fibres often run into the epithelium to end in intra- and extra-gemmal fibres. The terminal fibres frequently show marked change in size and within the epithelium, often end bluntly or in small knobs.The facies inferior linguae of the newborn dog is generally surfaced by a thin smooth non-cornified stratified flat epithelium. The propria here is also rather thin, and the papillae growing out of the propria into the epithelium are usually very ill developed, but somewhat larger papillae are found near the median line. A few longitudinal mucous folds are formed on the facies inferior.The facies inferior contains only very ill-developed proprial plexus, and consequently, the sensory fibres therein are also very scanty. The sensory terminations here too are of unbranched and simple branched types only