On the Innervation of the Snout and the Nasal Cavity of Cat in the Last Fetal Stage

Abstract

The snout is already in nearly full formation in the last fetal stage, but shows some infantility. Its mucous membrane is covered by a stratified flat epithelium far thinner than in fetal cattle (ABE) and has epithelial sulci on its surface. At the bottom of these sulci are formed distinct cristae limitantes. Between these cristae, papillae are found developed. In the submucosa, neither snout glands nor sinus hairs can be discovered.The vestibula nasi have a catilaginous plate corresponding in shape to the inner vestibular moulding. The nasal septal cartilage stands on the median line and a semilunar cartilaginous arch extends on either side of it. A cartilaginous process juts out from a point somewhat lower than the mid-point of either arch. This closed cartilage is lined with a mucous membrane on its inside, the epithelium is a a stratified flat one far thinner than that of the snout and forms no epithelial sulci. Conspicuous papillae, however, are still in formation in the foremost part adjacent to the snout. Nasal glands are well developed in the areas where the mucous membrane is thick but absent in the areas where it is thin, in the deep parts of the vestibulum. The backmost part of the vestibule is covered by a stratified cylindrical epithelium.The pars respiratoria of the nasal cavity is under a ciliated epithelium and nasal glands and venous plexus are in very good development in the submucosa beneath, but no smooth muscle fibres are found among the veins.The snout of fetal cat of last stage is already richly supplied with sensory fibres. Very uumerous thick sensory fibres are found in the submucosal and the proprial plexus. Most of the sensory fibres run toward the epithelial cristae and a fewer toward the papillae. A small part of the former end subepithelially in branched terminations, but the larger part run further into the cristae to end similarly. These are already rather complexly constructed, their terminal fibres are thick and mostly show frequent change in size in their short and peculiar winding courses before ending sharply. Fibres that run up in rather long courses close to the superficial layer of the epithelium are not rare either. It is of interest that such terminations were found in all the cristae examined. The sensory terminations in the papillae are very scanty, and these few are nothing more complex than the simplest unbranched terminations.Arterio-venous anastomoses were often found in the submucosa of the snout and the foremost part of the vestibulum nasi of my cat's fetus. These are not only very richly provided with terminations of vegetative fibres (STOHR's terminal reticula), but also contain a comparatively large number of terminations of thick sensory fibres. Their terminal fibres show frequent change in size and often penetrate into the epitheloid cell layer before ending.Sensory nerve fibres are found also rather numerous in the vestibulum nasi, and most of them are found in the parts adjoining the snout. As the deeper part of the vestibulum is reached, the number of sensory fibres decreases very rapidly, especially in the area where the mucous membrane is thin.The mucous membrane covered by a thick papillae-containing epithelium in the part of the vestibulum nasi adjoining the snout also contains many sensory fibres, though not so many as in the snout. These usually enter the cristae to form intraepithelial branched terminations. The terminal fibres of these also show marked change in size and peculiar looped courses. A small number of unbranched and simple branched terminations are found in the papillae as well.In the parts of mucous membrane outside the areas provided with epitelial cristae and papillae in the vestibulum, the formation of proprial plexus is feeble, so that sensory fibres are also limited in number; these few sensory fibres end subepithelially in unbranched and simple branched terminations.