NERVES OF THE NECK. 365 



2. The hypoglossal nerve, the twelfth cranial, is a stout 

 nerve which leaves the skull by the condylar fora- 

 mina, immediately behind the foramen lacerum 

 posterius, and lies at first very close to the pneumo- 

 gastric, glosso-pharyngeal, and spinal accessory 

 nerves. Outside the skull it runs downwards and 

 inwards for about half an inch, and then turns 

 forwards, crossing the internal carotid artery near 

 the point of division of the carotid into internal 

 and external carotids. It then runs forwards and 

 inwards along the dorsal surface of the stylo-hyoid 

 muscle, and parallel to the posterior cornu of the 

 hyoid, to the base of the tongue, in the muscles of 

 which it ends. 



The hypoglossal nerve is readily found, where it horns for- 

 wards between the carotid artery and the stylo-hyoid mtiscle; 

 it should be followed from this point bachvards to the skull, 

 and forwards to the tongue. 



a. The ramus descendens is a branch of the hypo- 

 glossal, which arises from the main nerve just be- 

 fore it reaches the internal carotid artery. It runs 



Fio. 63.— Lepus cuniculus. Dissection to show tlie nerves of the neck. 

 The hinder part of the trachea is puslied slightly to the right side, 

 and the thyroid body is removed. Two-thirds natural size, 

 (c. H. H.) 



AC, right carotid artery. AD, ductus arteriosus, with loop of left recur- 

 rent laryngeal nerve passing behind it. AO, arch of aorta. AP, root of 

 pulmonary artery. AS, right subclavian artery, with loop of right recurrent 

 laryngeal nerve passing behind it. 



MA, mandibular muscle. MD, stylo-hyoid muscle. MH, sterno-hyoid 

 muscle ; the sterno-thyroid is seen at the hinder end where both muscles are 

 cut across. MM, sterno-mastoid muscle. MV, posterior cornu of hyoid. 

 MW, clavicle. 



TSijr, glosso-pharyngeal nerve. P, anterior and posterior portions of right 

 pneumogastric nerve. The middle portion has been removed. PA, left pneu- 

 mogastric nerve. PB, ganglion of the pneumogastric nerve. PC, anterior 

 laryngeal nerve. PD, depressor nerve. PR, PS, right and left recurrent 

 laryngeal nerves. Q, spinal accessory nerve. E, hypoglossal nerve. RD, 

 descending ramus of the hypoglossal : its connections with the first and second 

 spinal nerves are not shown. SB. great auricular nerve arising from the 

 third cervical spinal nerve. SC, SD, SE, fourth, fifth, and eighth cervical 

 spinal nerves. SH, SK, right and left phrenic nerves : the anterior portion 

 of the left one has been removed. SL, cervical sympathetic nerve. SM, 

 anterior cervical ganglion. SUV, middle cervical ganglion. 



TM, submaxillary gland. TW, Wharton's duct. TP, oesophagus. TR, 

 trachea. TV, lung. TTV, diaphragm. TZ, ear, cut off short. VL, VB, 

 left and right anterior vense cavw. 



