GREAT VESSELS AND NERVES OF NECK 223 



in the thorax, and hooks round the aortic arch. In the 

 neck, each recurrent nerve ascends in the groove between 

 the trachea and oesophagus, along the medial side of the 

 corresponding lobe of the thyreoid gland, and, passing 

 posterior or anterior to the inferior thyreoid artery, it dis- 

 appears, 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 them 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. The accessory nerve consists of two 

 parts a spinal and a cerebral. In the jugular foramen the 

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

 jugular ganglion of the vagus, and below the base of the 

 skull 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 backwards 

 below the level of the transverse process of the atlas. It 

 crosses the internal jugular vein, and disappears into the 

 sterno-mastoid muscle. Its further course has been studied 

 already (pp. 41 and 133). It is distributed to two muscles 

 viz., the sterno-mastoid and the trapezius. 



Plexus Pharyngeus. The pharyngeal plexus 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 

 its construction, and one or more minute ganglia are 

 developed in connection with it. Its terminal twigs are given 



