164 Anatomy of thi: Rabbit. 



divided — the latter at the base of the tongue — so that the external 

 carotid artery may be displaced backward. 



(a) The ninth (glossopharyngeal) nerve is farthest forward. Its 

 two main branches are the ramus lingualis to the tongue, 

 and the ramus pharyngeus, the latter entering the lateral 

 wall of the pharynx. 



The tenth (vagus) nerve bears an elongated ganglionic enlargement, 

 the plexus ganglioformis (ganglion nodosum). It lies immediately 

 below the jugular foramen. 



The superior laryngeal nerve and the ramus cardiacus are given off 

 at the level of the origin of the internal carotid artery. 



The eleventh cranial, or spinal accessory nerve (n. accessorius) is 

 dorsal to the vagus, with which it is united above the plexus ganglio- 

 formis by a ramus internus. The nerve passes dorsad to the medial 

 side of the mastoid attachments of the sternohyoideus and cleidomas- 

 toideus muscles, giving branches to the latter, and then passes backward 

 to the ventral surface of the trapezius to which it is distributed. 



The twelfth (hypoglossal) nerve arises behind the foregoing nerves, 

 since it conies from the hypoglossal foramina of the occipital. It 

 crosses their roots, forming a broad curve on the lateral surface of the 

 root of the external carotid artery and enters the base of the tongue. 

 The ramus descendens is given off at about the point where it crosses the 

 artery. 



The cervical portion of the sympathetic trunk begins in the superior 

 cervical ganglion (g. cervicale superius). It lies to the medial side of the 

 vagus ganglion and of the internal carotid artery. The nerves 

 proceeding from the ganglion accompany the branches of the external 

 and internal carotid arteries to the head. 



9. The oral cavity and pharynx. 



The glossopharyngeal nerve and the superior laryngeal nerve and 

 artery may be divided, and the external carotid artery with the associ- 

 ated nerves separated from the oesophagus and trachea. The latter may 

 be displaced downward to a slight extent by dividing the loose con- 

 nective tissue along the ventral surface of the vertebral column. An 

 incision extending from the anterior end of the oral cavity backward into 

 the oesophagus will expose the internal surface of the digestive tube 

 sufficiently to make out its features. The incision divides the con- 

 strictor pharyngis muscle, a broad band of muscle fibres enclosing the 

 posterior portion of the pharynx. 



The general divisions are: 



(a) The oral cavity (cavum oris), divisible into the oral cavity 

 proper, and the vestibulum oris, the latter lying between the 

 alveolar processes and teeth on the one hand and the lips on 

 the other. 



(b) The pharynx: its oral portion (pars oralis) continues the orq,l 

 cavity, and connects it with the oesophagus. Its dorsal, 

 also anterior, nasal portion (pars nasalis), or nasopharynx. 



