X. N. vagus.

—The vagus nerve arises from the side of the medulla in the manner described under the Brain ([page 346] and [Fig. 138], X). It passes through the jugular foramen along with the glossopharyngeal and accessory nerves.

Cervical Portion of the Vagus ([Fig. 156], d, d′).—In the foramen, or just before entering it, it presents a ganglionic enlargement, the ganglion jugulare (or “ganglion of the root”), and a short distance beyond the foramen it forms a second ganglion, the ganglion nodosum (d) (or “ganglion of the trunk”), which lies dorsocaudad of the superior cervical sympathetic ganglion (e). The ganglia of the vagus and sympathetic are closely bound together by connective tissue, and that portion of the vagus craniad of the ganglion nodosum is interconnected by a network of nervous fibres with the sympathetic (e), hypoglossal (b), and accessory (c) nerves. From the ganglion nodosum the vagus (d′) passes caudad, closely bound up with the sympathetic; the two lie at the side of the common carotid artery. Just before entering the thorax the two separate, the vagus being the larger and lying ventrad of the sympathetic. (In rare cases the two are distinctly separated throughout their length.)

[Fig. 156].—Glossopharyngeal, Hypoglossal, Vagus, Sympathetic, and First Cervical Nerves in the Neck.

a, N. glossopharyngeus; b, N. hypoglossus; c, N. accessorius; d, ganglion nodosum of vagus nerve; d′, N. vagus; e, ganglion cervicale superius of sympathetic; f, ramus descendens of N. hypoglossus (united with first cervical); g, branch to M. thyrohyoid from ramus descendens of N. hypoglossus; h, N. laryngeus superior of N. vagus; i, united vagus and sympathetic nerves; j, first cervical nerve; k, second cervical nerve; l, N. pharyngeus from vagus. 1, M. masseter; 2, outline of external ear; 3, M. splenius; 4, M. levator scapulæ ventralis; 5, M. longus capitis; 6, trachea; 7, M. sternothyreoideus; 8, M. sternohyoideus; 9, M. thyreohyoideus; 10, M. constrictor pharyngis inferior; 11, M. constrictor pharyngis medius; 12, cut end of M. stylohyoideus; 13, M. hyoglossus; 14, M. stylopharyngeus; 15, bulla tympani; 16, M. jugulohyoideus; 17, M. styloglossus; 18, M. mylohyoideus.

Branches of the vagus in the cervical region ([Fig. 156]).

a. N. auricularis.—This leaves the ganglion jugulare, passes into the petrous bone to the facial canal, leaves the skull with the facial nerve by the stylomastoid foramen, and is distributed to the external ear.

b. N. pharyngeus (l).—This leaves the vagus craniad of the ganglion nodosum, passes ventrad, sends a small communicating branch to N. laryngeus superior (h), and is distributed to the pharyngeal muscles and cranial part of the œsophagus.

c. N. laryngeus superior (h).—This arises from the ganglion nodosum, passes ventrad, crossing the medial surface of the carotid artery, and reaches the larynx at about the level of the caudal end of M. thyreohyoideus. It passes into the larynx and supplies its mucosa.