244 



Anatomy of the Rabbit. 



(i) 



(J) 



(c) 



The twelfth cranial or hypoglossal nerve (n. hypo- 



glossus) enters the base of the tongue. It lies on the lateral 

 side of the external carotid artery and. on the medial side of 

 the stylohyoideus major. It is distributed as a motor nerve 

 to the lingual muscles. 



The ramus lingualis of the ninth cranial, or glosso- 

 pharyngeal nerve (n. glossopharyngeus) enters the base of 

 the tongue at a point dorsal to the hypoglossus and between 



the stylohyoideus minor and the stylo- 

 pharyngeus. It is a gustatory nerve of 

 the tongue. 

 S. Dissection of the extra-cranial roots of 

 the ninth to twelfth nerves (Fig. 79). 



These nerves, which for the most part have 

 already been exposed, may be traced to their 

 origin in the jugular and hypoglossal foramina. 

 The tympanic bulla should be cleared and 

 the tendons of origin of tongue muscles 

 removed from the jugular process. 



(a) The ninth (glossopharyngeal) nerve 

 is farthest forward. Its two main 

 branches are the ramus lingualis to 

 the tongue, and the ramus pharyn- 

 geus, the latter entering the lateral 

 wall of the pharynx. 



(b) 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 

 (depressor nerve) 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. The nerve passes dorsad 

 to the medial side of the mastoid attachments of the sterno- 

 hyoideus and cleidomastoideus muscles, giving branches 

 to the latter, and then passes backward to the ventral surface 

 of the trapezius to which it is distributed. 



Fig. to. Plan of the 

 extra-cranial roots of the 

 IX-XII cranial nerves and 

 sympathetic trunk; vential 

 surface, right side, the 

 sympathetic and depressor 

 nerve shown as displaced 

 from the dotsal surface of 

 the artery, o, 10, n, 12, 

 glossophaiyngeal, vagus, 

 spinal accessory, and hypo- 

 glossal nerves; ac, carotid 

 artery; c, cervical root of 

 ramus descendens XII; 

 gn, ganglion nodosum vagi; 

 Is, superior laryngeal; nd, 

 depressor nerve; rd, ramus 

 descendens hypoglossi; s, 

 sympathetic. 



