GREAT VESSELS AND NERVES OF NECK 315 



from the vagus as the latter crosses the first part of the 

 subclavian artery, it hooks round the artery and ascends to 

 its termination. On the left side, it arises in the thorax, 

 and hooks round the aortic arch. In the neck each nerve 

 ascends in the groove between the trachea and oesophagus, 

 along the medial side of the lateral lobe of the thyreoid 

 gland, and, passing posterior or anterior to the inferior 

 thyreoid artery, it disappears as the inferior laryngeal nerve 

 under cover of the lower border of the inferior constrictor 

 muscle, and enters the larynx. 



Before the recurrent nerve reaches the larynx it gives 

 off several branches viz., (i) cardiac branches; (2) twigs 

 to the trachea and oesophagus ; and (3) a few filaments to the 

 inferior constrictor as it passes under cover of its lower margin. 



Cardiac Branches. Two cardiac branches arise from the 

 vagus in the neck. On the right side, both of these enter 

 the thorax by passing posterior to the subclavian artery and 

 they end in the deep cardiac plexus. On the left side, the upper 

 nerve joins the deep cardiac plexus, whilst the lower nerve 

 enters into the formation of the superficial cardiac plexus. 



Nervus Accessorius. This nerve consists of two parts 

 a spinal and a cerebral. In the foramen jugulare the cerebral 

 portion is connected by one or two fine twigs with the jugular 

 ganglion of the vagus, and below the basis cranii it leaves 

 the spinal part and joins the vagus. 



The cerebral part of the accessory nerve contributes to the vagus 

 the greater proportion of its motor fibres. They pass over the surface 

 of the ganglion nodosum, and are continued into the pharyngeal and 

 into the superior laryngeal nerves. Some of the fibres are carried down 

 the stem of the vagus into the cardiac branches and also into the recurrent 

 nerve. 



The spinal part of the accessory is directed posteriorly 

 under the transverse process of the atlas. It crosses the 

 internal jugular vein, and disappears into the substance 

 of the sterno-mastoid muscle. Its further course has been 

 studied already (pp. 147 and 150). It is distributed to two 

 muscles viz., the sterno-mastoid and the trapezius. 



Plexus Pharyngeus. This is a mesh-work of fine 

 nerve filaments, which is formed upon the wall of the 

 pharynx at the level of the middle constrictor muscle. 

 The pharyngeal branches of the vagus, glosso-pharyngeal, 

 and superior cervical ganglion of the sympathetic enter into 



