GICAL ANATOMY OF TILE NECK.
The posterior parts of the neck having been described in a previous article (see BAcK), the present will be restricted to an account of its anterior aspect.
The cervical vertebrx (by their bodies, inter vening fihro-cartilaginous discs, and transverse processes), together with the anterior and la teral vertebral muscles, already described, com pose the skeleton and supporting fabric of this region ; the anterior fibres of the trapezii, as they descend on either side to the inner edge of the acromio-clavicular arch, form its lateral boundaries ; the larynx and trachea (covered by their own extrinsic riband-like muscles, and partly covering the pharynx and (esophagus) separate the nearly symmetrical halves of the neck by constituting alonz its median line a raarked columnar relief, in the recesses beside which lie the great cervical vessels ; the base of the skull and the oblique line of the jaw are the upper limits of the region ; the clavicle (just behind which the great vascular and ner vous trunks of the upper extremity course) bounds it below ; the skin, the platysnia myoides (in its cellular covering), and the cer vical aponeurosis are stretched across it as ge neral itivestments ; while the last-named fascia ensheathes the various parts by special pro cesses from its deeper surface.
Thus, in general terms, the structure of the neck may be described ; but, for the more pre cise and particular account, which the impor tance of its anatomy renders necessary, a division of it into spaces of small extent is convenient. The arrangement, which I propose following, differs but little from that usually adopted, and, perhaps, somewhat exceeds it in precision.
The upper limits of the neck having been stated as the oblique line of the jaw and the base of the skull (which parts, as we shall pre sently see, are brought into relation by the attachments of the constrictor pharyngis supe rior), our highest region has in that direction these parts for its boundary, and extends below as far as the curve of the muscle, from which it is named the digastric space.
A small space that can hardly be referred to the digastric,—from which it is separated by the vaginal process of the temporal bone, and by attachments of fascia,—and which, from the im portance of its contents, deserves careful consi deration, is the posterior pharyngeal ; it lies closely beneath the base of the skull, (from the vaginal process to the median line) between the pharynx and spine, and includes the carotid, jugular, and condylie canals, and the organs traversing them.
If now an oblique line be carried across the neck, from the sterno-clavicular articulation to the tip of the mastoid process, it divides, as a diagonal, the remaining quadrilateral surface of the neck into two triangles ; an anterior one having its apex at the sterno-clavicular joint, and its base along the posterior belly of the digastric muscle; a posterior one, having, its base at the inner two-thirds of the cla vicle,—its apex at the mastoid proccsi,—its posterior side formed by the trapezins,—its an terior border defined by the imaginary I ne which demarks it from the anterior triangle. The omo-hyoid muscle, in its reflected course, crosses both these triangles, subdividing them ; and since the angle of its bend falls just on the line of their separation, and since it proceed.; from behind the outer third of the clavicle to the body of the hyoid bone, it acts as a second diagonal in the neck, dividing each into an upper and a lower triangular space. These four triangles will be described in detail ; and since the sterno-inastoid (which is too sub stantial to be treated as a mere boundary-line) enters into all of them, and has to parts of each relations of the extremest practical importance, some separate, chiefly recapitulatory, consi deration will be given to its relative anatomy. Finally, to ensure for the organs of the median line the consideration they reqnire (the useful ness of which mainly depeuds on their being viewed connectedly), it may be well to take them in that relation.