852 THE NERVOUS SYSTEM OF THE DOG 
to the common carotid artery. The two nerves separate after entering the thorax 
(Figs. 613, 614). The right vagus crosses obliquely over the right face of the 
trachea and divides a short distance behind the bifureation of the latter into dorsal 
and ventral branches. The left vagus crosses the lateral surface of the aortic arch 
and divides similarly. By the union of the dorsal and ventral divisions of the two 
nerves there are formed dorsal and ventral cesophageal trunks. The dorsal trunk 
concurs with branches of the cceliac plexus in forming the posterior gastric plexus 
on the visceral surface of the stomach. The ventral trunk ramifies on the parietal 
surface of the stomach, forming the anterior gastric plexus, from which a consider- 
able branch passes along the lesser curvature to the pylorus. Some special features 
of the collateral branches are: Two pharyngeal branches are present. The anterior 
pharyngeal branch arises from the vagus above the ganglion nodosum. It passes 
under the deep face of the carotid artery and descends on the lateral surface of the 
pharynx to endin the crico-thyroid muscle. It furnishes a root of the inferior pharyn- 
geal branch, and communicates with the pharyngeal branch of the ninth and with the 
Fic. 683.—Nerves OF Face or Doc. Parotrp GLAND IS REMOVED. 
Nerves: a, Facial; b, posterior auricular; c, internal auricular; d, digastric; e, inferior buccal; f, cervical branch 
of facial; g, auriculo-palpebral; A, superior buccal; 7, temporal branch; &, 4’, &’’, zygomatic branch; /, auriculo-tem- 
poral; m, malar branch of 1; n, buccinator; 0, mylo-hyoid branch; p, subcutaneus male; gq, lacrimal; r, frontal; s, 
infratrochlear; ¢, infraorbital. 1, Paramastoid process; 2, occipito-mandibularis; 3, base of concha; 4, masseter; 
6, zygomaticus; 6, scutularis; 7, zygomatic arch; 8, maxilla. (Ellenberger-Baum, Anat. d. Hundes.) 
anterior laryngeal and hypoglossal nerves. The posterior pharyngeal branch is 
formed by the union of roots derived from the anterior pharyngeal nerve and the 
ganglion nodosum, together with filaments from the anterior cervical ganglion. 
It crosses the side of the pharynx behind the anterior pharyngeal and ramifies on 
the posterior constrictor of the pharynx and the origin of the cesophagus. It 
contributes filaments to the pharyngeal plexus, communicates with the recurrent 
nerve, and supplies twigs to the thyroid gland. The pharyngeal plexus is formed 
on the lateral surface of the pharynx by branches of the pharyngeal nerves and the 
communications above described; branches from it innervate the muscles and 
mucous membrane of the pharynx. The anterior laryngeal nerve arises from the 
ganglion nodosum and descends over the side of the pharynx, crossing beneath the 
carotid artery and the anterior laryngeal nerve. It passes through the thyroid 
notch and ramifies in the mucous membrane of the larynx. It communicates with 
the anterior cervical ganglion and the anterior pharyngeal branch of the vagus, and 
gives twigs to the hyo-pharyngeus muscle. Immediately after its entrance into the 
larynx it gives off a large branch which, instead of uniting with the recurrent as in the 
