Page:Muscles and Regions of the Neck.djvu/13

Rh viewed connectedly), it may be well to lake them in that relation.

Thus, (1) a region of the median line, (2) an antero-inferior, (3) an antero-superior, (4) a postero-superior, and (5) a postero-inferior triangle, (6) a digastric, and (7) a posterior pharyngeal space, are to be severally considered; and a few preliminary remarks may be given to the tegumentary parts, which are more or less common to all.

The skin is fine, thin, and extensible, especially below and in front; becoming coarser and more adherent toward the upper part of the posterior triangle; it frequently presents some transverse wrinkling above the hyoid bone, which seems to depend on the platysma myoides; here, too, the follicles are larger and more abundant than in the other parts of the neck, and, in the male subject, the surface is overgrown by the beard. The subcutaneous cellular tissue has already been described; in the upper part of the posterior triangle it becomes almost inseparably confounded with the cervical aponeurosis; the platysma myoides lies between its layers and keeps them apart over the greater surface of the neck; the fibres of this muscle are absent in the lower part of the anterior, and upper part of the posterior triangle, and at these spots the two layers of the superficial fascia fall together and are nearly confounded. In the deeper lamina of this texture, subjacent to the platysma in the parts where it lies, run the superficial veins and nerves. The external jugular vein commences in the parotid gland, usually by radicles, which correspond to the terminal branches of the external carotid artery, temporal, internal maxillary, and transverse facial; pierces the fascia near the angle of the jaw, and directs itself almost vertically toward the middle of the clavicle, in the deep layer of superficial fascia; just at the edge of the clavicular insertion of the sterno-mastoid muscle it bends inward, pierces the aponeurosis, and discharges itself into the subclavian vein. It thus very obliquely crosses the sterno-cleido-mastoideus from its anterior to its posterior edge, separated from that muscle by its fascial sheath; the auricular nerve runs upward parallel to its posterior border; the platysma covers it in its whole course with fibres which cross its direction; its place of discharge into the subclavian vein is usually just opposite the scalenus anticus, covered by fascia and by the sterno-mastoid muscle. It receives superficial occipital, superior and posterior scapular veins; branches from the posterior triangle of the neck, and from the trapezius; it has uncertain and irregular communication with the anterior jugular vein, and receives a certain, though not regular, branch from the internal jugular; this is usually given to it at the lower part of the parotid, or on its emergence from that gland, and occasionally seems to constitute its commencement. Obvious surgical inferences from the anatomy of this vein are: the relief that its communication with the internal jugular enables it to give, when opened in cases of cerebral congestion; the eligibility of its line of passage over the thick belly of the sterno-mastoid for that mode of venesection; the necessity for dividing some fibres of the platysma transversely to their length (by an incision nearly in the direction of the sterno-mastoid) in order to obtain a clear opening and free jet of blood; the need for care in this operation, but still more in proportion as the vein is wounded lower in the neck, to hinder the possibility of air being inspired through its cavity.

The anterior jugular vein is an irregular subcutaneous supplement to the external: it commences in the submental region, near the hyoid bone; descends vertically beside the median line, receiving branches from the larynx, and sometimes from the thyroid body; on arriving at the sternum, or near that bone, it bends horizontally outward, piercing the fascia, and runs behind the origin of the sterno-mastoid, to throw itself into the subclavian vein, somewhat within the termination of the external jugular. It generally has free communications with its fellow and with the internal and external jugular. Its size is in inverse proportion to that of the external; and, in absence of this, it is generally a very considerable branch; it is sometimes single and mesial; but more usually two exist, which are commonly of unequal calibre.

The superficial nerves are of two classes, being partly derived from the cervical plexus, partly from the portio dura.

The cervical plexus sends its superficial branchings in three directions: the mastoid and auricular pass upward; the anterior cervical runs forward; the supra-clavicular and super-acromial, as their names denote, descend more or less obliquely.

The mastoid, originating from the second cervical nerve, winds upwardly across the splenius, and almost parallel with the posterior edge of the sterno-mastoid, which it crosses in its ascent. It pierces the fascia soon after its origin, and becomes subcutaneous. Its distribution is entirely to the skin of the mastoid and occipital regions. The auricular, rising from the second and third cervical nerves by a trunk, common to it with the anterior cervical, directly pierces the fascia, loops round the posterior edge of the sterno-mastoid, and ascends across its surface (the fascial sheath intervening) toward the angle of the jaw; where, after supplying twigs to the integuments over the parotid gland, it divides into terminal branches, which are distributed to the external and internal surfaces of the auricle and to the adjoining integument, in a manner which need not be particularised in the present article. In crossing the sterno-mastoid it is parallel to the external jugular vein, and behind it. The anterior cervical rises in common with the last, and pierces the fascia in its company; bends at right angles across the sterno-mastoid muscle, and is itself crossed by the external jugular vein. On arriving at the edge of the muscle, it divides into many twigs, which, traversing the platysma at several spots, distribute themselves to the skin of the anterior triangle of the neck, and to that of the adjacent part of the digastric