Page:Muscles and Regions of the Neck.djvu/24

22 a partial septum, divides a superficial space from the general submucous tract; and it is necessary to understand this arrangement, in order to apprehend the mode in which the sub-maxillary gland approaches the mucous membrane of the mouth: the gland lies in the superficial division of the space, and it is round the posterior edge of the mylo-hyoid muscle that its duct is reflected in proceeding to discharge itself, which by so entering the sublingual space it is enabled to do. The anterior division of the digastric space contains, superficially the gland just mentioned, the facial artery and vein with some of their branches, the mylo-hyoid twig from the third division of the fifth, and many lymphatic ganglia. The gland receives a thin capsular investment from the deep surface of the fascia, closing the space, and this prolongation contracts and condenses itself round the posterior extremity and duct, accompanying these in their turn round the mylo-hyoid, and furnishing the duct with a dense fibrous tunic. The artery enters the space from below, by passing beneath the posterior belly of the digastric muscle, very tortuously winds through the submaxillary gland, and bends over the basial edge of the jaw a little in front of the masseter. It furnishes a deep ascending branch (the tonsillary) near the angle of the jaw and many glandular twigs; but its only considerable branch in this region is the sub-mental, which runs toward the median line just beneath the jaw, and, supplying the mylo-hyoid muscle on which it is applied, and the anterior belly of the digastric, terminates by freely communicating with its fellow. The sub-mental branch derives additional importance from the frequency of an anomalous distribution, by which, piercing the mylo-hyoid muscle and entering the sublingual space, it partly discharges the functions of the lingual artery in supplying the sublingual gland. The facial vein lies behind the artery, and quits the space below in passing over the digastric and stylo-hyoid muscles, which divide it from the artery. Its usual or chief termination is in the internal jugular; but it frequently contributes more or less to form the external or the anterior jugular vein. The mylo-hyoid nerve runs parallel to the origin of the muscle, which gives it its name, and supplies it and the anterior belly of the digastric. The lymphatic glands are numerous and important: they receive the absorbent vessels from the face and likewise from the mouth and pharynx, are the frequent seat of strumous inflammation, readily sympathize in disordered conditions of the fauces and alveoli, and take an active part in propagating the malignant influence of cancerous ulcerations on the face. These parts are all covered in by the aponeurosis,—which fixes itself to the base of the jaw,—and by the platysma and superficial fascia,—which continue themselves on the face. They are readily accessible to the surgeon, but seldom subjected to any operation of importance. The deep or sublingual portion of the digastric space has its roof formed by the mucous membrane, which, between the tongue and alveolar arch, constitutes the floor of the mouth: the side of the tongue and the continuous surface of the pharynx, as already described, compose its inner wall; and it follows from the previous description that, in part at least, the mylo-hyoid is its floor. The gustatory nerve runs through it beneath the mucous membrane, which it supplies: the hypo-glossal, describing a parallel but inferior curve, is distributed in succession to the muscles of the inner wall of the space; the glosso-pharyngeal between these two in height, but confined to the root of the tongue, bends inwardly beneath the stylo-glossus; the lingual artery, emerging from under cover of the hyo-glossus, which has hidden its tortuous ascent, divides anteriorly into two branches; a ranine, which follows the curved border of the tongue to its tip, where it archingly unites with its fellow; a sublingual, which directing itself a little outward, supplies the third salivary gland: this little body lies on the divergent fibres of the genio-glossus, near their origin, and close beneath the membrane of the mouth: finally, the duct of the submaxillary gland, traversing the space obliquely, crosses its contents, and communicates with the cavity of the mouth just beside the frœnum. This space is the seat of ranula (a tumour formed by obstruction of the submaxillary duct), and of some salivary concretions; in both which complaints the distended canal isbrought so immediately beneath the mucous membrane, which it raises, that other parts are little liable to injury; here, too, it is that the surgeon, when obliged to divide the frœnum linguæ, must cautiously cut the too tight fold near to the symphysis, and vertically, lest, in extending his incision backward, he should wound the ranine artery. Sharp instruments penetrating downward beside the tongue may wound the sublingual artery, and the consequent hæmorrhage, distending the submucous space, raise the reflected membrane on each side into swellings of such size, as to suggest imminent peril of suffocation.

7. The small region to which, under the name of posterior pharyngeal, I propose giving brief notice, has for its roof the basilar portion of the occiput and petrous part of the temporal bone, and presents in this direction the orifices of the jugular, carotid, and anterior condylic canals: it extends downwards between the pharynx and vertebræ into the anterior triangle of the neck, and is separated from the posterior division of the digastric space, within which it lies, by the styloid and vaginal processes, and by the attachment to these of a strong layer of fascia, which passes beneath the digastric muscle. The internal carotid artery, surrounded by branches from the superior cervical ganglion,