800 



NERVOUS SYSTEM OF THE HORSE 



small superficial petrosal nerve from the tympanic plexus, through which communi- 

 cations are made with the facial and glosso-pharyngeal nerves. Sympathetic 

 fibers are derived from the plexus on the internal maxillary artery. Efferent fila- 

 ments go to the tensor palati, tensor tympani, and pterygoid muscles and to the 

 Eustachian tube. 



The ganglion is small and somewhat difficult to find, and in many cases it is replaced by 

 a number of minute ganglia interspersed in a fine plexus. 



5. The superficial temporal nerve (N. temporalis superficialis) (Figs. 562, 

 646, 647) runs outward across the pterygoideus lateralis, passes between the parotid 

 gland and the neck of the ramus of the mandible, turns around the latter, and di- 

 vides into two branches. The transverse facial branch (Ramus transversus faciei) 

 accompanies the transverse facial vessels and ramifies in the skin of the cheek. 

 The larger ventral branch unites with the ventral buccal division of the facial nerve. 

 Before its division the nerve gives off twigs to the guttural pouch, the parotid 

 gland, the external ear, and the skin of the external acoustic meatus and the mem- 



FiG. 048. — Pakt of Bbanch of Lower Jaw of Hohse; Medial View. 

 The bone haa been removed to show the vessels and nerves. 1,1', Mandibular alveolai; nerve; 2 

 cheek teeth and gums; 2', branch to camne and incisor teeth; 3, 3', alveolar artery; 4. satellite vein, 

 ing's Atlas.) 



2, branches to 

 (After Leiser- 



brana tympani. Branches from it concur with filaments from the cervical branch 

 of the facial nerve in the formation of the auricular plexus. 



6. The mandibular alveolar nerve (N. alveolaris mandibulse) (Figs. 561, 562, 

 646)^ arises with the lingual by a common trunk which passes forward at first on 

 the lateral pterygoid muscle, then inclines ventrally between the medial pterygoid 

 and the ramus of the mandible. The lingual and alveolar separate at an acute 

 angle, and the latter enters the mandibular foramen and courses in the canal 

 within the ramus (Fig. 648). Emerging at the mental foramen, it terminates by 

 dividing into six to eight inferior labial and mental branches, which ramify in the 

 lower lip and chin. Before entering the bone, the nerve detaches the mylo-hyoid 

 nerve (N. mylohyoideus), which runs downward and forward between the ramus 

 and the mylo-hyoid muscle; it supplies that muscle, the anterior belly of the 

 digastricus, and the skin of the anterior part of the mandibular space. The dental 

 and gingival branches detached from the nerve Avithin the mandible are arranged 

 like the corresponding nerves of the upper jaw. 



7. The lingual nerve (N. lingualis) arises by a common trunk with the mandib- 

 ular alveolar nerve (Figs. 561, 562). After separating from the latter it runs 



"■ Also termed the inferior dental nerve. 



