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 bifurcation 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 oesophageal trunks. The dorsal tnink 

 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 end in 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 



Fig. 683. — Nerves of Face of Dog. Parotid Gland is Removed. 

 Nerves: a, Facial; 6, posterior auricular; c, internal auricular; d, digastric; e, inferior buccal; /, cervical branch 

 of facial; g, auriculo-palpebral; h, superior buccal; i, temporal branch; k, k' , k" , zygomatic branch; I, auriculo-tem- 

 poral; m, malar branch of I; n, buccinator; o, mylo-hyoid branch; p, subcutaneua malte; q, lacrimal; r, frontal; s, 

 infratrochlear; t, infraorbital. U Paramastoid process; £, occipito-mandibularis; 3, base of concha; 4t masseter; 

 6, zygomaticus; 6, scutularis; 7, zygomatic arch; 8, maxilla. (EIlenberger-Baum, Anat. d. Hundes.) 



anterior laryngeal and hypoglossal nerves. The posterior pharjoigeal 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 phar3mgeal 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 

 ] arynx it gives off a large branch which, instead of uniting with the recurrent as in the 



