NERVES OF THE NECK. * 375 



The sole difficulty in dissecting the anterior laryngeal nerve 

 lies in the possibility of confusing it with the ramus descendens 

 of the hypoglossal. This is avoided if it be remembered that, 

 while both nerves cross the carotid artery, the ramus descendens 

 lies ventral to the artery, and the anterior laryngeal, dorsal 

 to it. 



The depressor nerve is a very slender branch of 

 the anterior laryngeal nerve, which runs 

 backwards along the neck : it lies dorsal to 

 the carotid artery, and along the inner side 

 of the main stem of the pneumogastric nerve, 

 very close to the sympathetic nerve-trunk. 

 It ends in the heart. 



Find the depressor nerve where it leaves the anterior laryngeal 

 nerve, about the level of the posterior end of the thyroid cartilage, 

 and follow it backwards along the neck. Its dissection in the 

 thorax is difficult. 



b. The right posterior or recurrent laryngeal nerve 

 arises from the pneumogastric nerve at the 

 posterior end of the neck. It loops round the 

 subclavian artery, and then runs forwards along 



Fig. 65. Lepus cuniculus. Dissection to show the nerves of the 

 neck. The hinder part of the trachea is pushed 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 - 

 reut laryngeal nerve passing behind it. AO, arch of aorta. AP, root of pul- 

 monary artery. AC, right subclavian artery, with loop of right recurrent 

 laryugeal 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 acro3s. MM, sterno-mastoid muscle. MV, posterior cornu of hyoid. MW, 

 clavicle. 



NG, 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. PG, anterior 

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

 laryngeal nerves. Q, spinal accessory nerve. R, 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. SN, middle cervical ganglion. 



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

 trachea. TV, lung. TW, diaphragm. TZ, ear, cut off short. VL, VR, left 

 and right anterior venae cavse. 



