4. Mucous membrane and glands.—The inte rior of the pharynx is lined by a mucous mem brane continuous with that investing the several cavities which open into it; it is of a reddish colour, and adherent to the muscular parietes by a thin submucous areolar tissue; from co vering the back part and sides of the interior of the pharynx, it is to be traced along the under surface of the basilar process united to the periosteum through the medium of its sub mucous tunic, which at this part acquires con siderable thickness, and is occasionally the seat of polypus; laterally and above it is reflected over the guttural orifice of the Eustachian tube, enters the canal, and is conducted by it to the cavity of the tympanum, forming an exceed. ingly thin lining to both; continuous with the mucous membrane, investing the upper surface of the velum, it passes through the posterior nasal openings into the nose; it may be next traced through the isthmus fauciutn, covering the under surface of the velum and posterior pillars of the fauces, to be continuous with the membrane of the buccal cavity, while more in teriorly, after assisting to form the aryteno epiglottidean folds of the laryngeal mucous membrane, it is reflected over the posterior surface of the larynx, to which it is connected so loosely by an areolar tissue as to be thrown into longitudinal folds, a provision for the dila tation of this part of the pharynx during the pas sage of the food ; lastly, it is continued into the (esophagus. The mucous membrane above the velum palati, upon its upper surface and within the Eustachian tubes, is coated with epithelial prisms, corresponding in this respect with that which lines the greater part of the nasal cavities, while below the velum the epithelium assumes the lamelliform or scaly character. (See Mu cous MEMBRANE.) As it invests the upper part of the pharynx its free surface presents numerous slight elevations occasioned by the glands which are situated beneath it ; these in deed are scattered over the whole pharynx, but are especially abundant at its upper part, where they form a compact lamina between its mus culo-membmnous tunic and the mucous mem brane, opening upon the surface of the latter by slender ducts.
5. Vessels and nerves. —The bloodvessels distributed to the pharynx are derived from several sources, but chiefly. from an especial trunk, viz. the ascending or inferior pharyngeal artery; this vessel arises from the posterior part of the extemal carotid, often its first branch, near the bifurcation of the common carotid ; it ascends to the base of the skull, lying close by the side of the pharynx and upon the rectus capitis anticus major muscle, sending off' nu merous small branches, which, intermingling with the pharyngeal plexus of nerves, are dis tributed to the constrictors and stylo-pharyn geus, to the velum, arches of the palate and tonsil, ending in minute ramifications on the mucous membrane ; the next most regular sup ply is from the inferior palatine and tonsillitic branches of the facial artery ; the internal max illary, lingual and superior thyroid vessels con tribute an irregular supply of small and unim portant twigs. The veins form a considerable
plexus, the pharyngeal venous plexus, which is produced chiefly by the frequent anastomoses of the pharyngeal vein with the small branches that accompany the inferior palatine and tonsil litic arteries, and with some of the commencing twigs of the internal maxillary vein ; the pha ryngeal vein, which receives the blood from this plexus, opens, either singly or in conjunc tion with the lingual, into the internal jugular vein ; of the lymphatics, but little is known ; they probably enter the chain of glands which lie along the outer side of the carotid sheath. An intricate plexus of nerves, the pharyngeal plexus, is situated upon the sides of the pha rynx, the branches being earticularly numerous upon the middle constnctor muscle near its origin ; it is of some length, and subject to variety in the number of its filaments in diffe rent subjects ; it interlaces with the ramifica tions of the arterial twigs from the ascending pharyngeal, and derives its branches from the three portions of the eighth pair of nerves and from the superior cervical ganglion of the sym pathetic ; the glosso-pharyngeal nerve sends downwards two or more branChes to the plexus; one of these I have seen to join the superior laryngeal nerve ; they are given off just before the nerve winds round the lower border of the stylo-pharyngeus muscle subsequently one or two bmnches penetrate this muscle to be distri buted to the pharyngeal mucous membrane ; the pneumo-gastric detaches one or two pharyn geal branches; the larger one appears in a great measure formed by a branch from the spinal accessory nerve; these join with the filaments from the glosso-pharyngeal ; the superior laryn geal nerve by its external branch also contri butes a few filaments ; lastly, from the superior cervical ganglion of the sympathetic, twigs are derived, which; communicating vvith those already mentioned, complete this intricate plexus ; the branches from it are distributed to the pharyngeal walls, to the soft palate, and stylo-pharyngeus muscles. The digastric branch of the facial nerve and the lingual or its de scending bmnch are described as sometimes communicating with this plexus : for the more minute anatomy of these nerves see PAR