222 HEAD AND NECK 



loop of the cervical plexus, and the superior cervical ganglion 

 of the sympathetic. Further, the hypoglossal nerve is gener- 

 ally closely bound to it by fibrous attachment, in the midst 

 of which some interchange of nerve filaments takes place. 



Branches of Distribution of the Cervical Part of the 

 Vagus. The branches which spring from the vagus as it 

 traverses the neck are the following: (i) pharyngeal ; 

 (2) superior laryngeal ; (3) recurrent; (4) cardiac. 



Ramus Pharyngeus. The pharyngeal branch springs 

 from the upper part of the ganglion nodosum and runs 

 downwards and forwards, superficial to the internal carotid 

 artery, to end in the pharyngeal plexus. It is frequently 

 replaced by two branches, of which the upper is the larger. 



Nervus Laryngeus Superior. The superior laryngeal 

 nerve, a much larger branch, arises from the middle of the 

 ganglion nodosum. It passes downwards and forwards, but 

 differs from the pharyngeal branch by passing deep to the 

 internal carotid artery. Whilst in that situation it ends by 

 dividing into the internal laryngeal and external laryngeal 

 nerves, both of which have been previously seen in the dis- 

 section of the anterior triangle (p. 132). 



Before it divides, the superior laryngeal effects communications, by 

 means of fine twigs, with the superior cervical ganglion of the sympathetic, 

 and it also receives one or two filaments from the pharyngeal plexus. 



The internal laryngeal nerve runs to the interval between 

 the hyoid bone and the thyreoid cartilage ; there, after 

 disappearing under cover of the posterior border of the 

 thyreo - hyoid muscle, it pierces the membrane of the same 

 name, and enters the pharynx, and then descends to the 

 larynx. 



The external laryngeal nerve is a very slender branch, which 

 inclines downwards and forwards to reach the crico-thyreoid 

 muscle, in which it ends. 



It supplies a few filaments to the inferior constrictor of the pharynx and 

 a fine twig to the superior cardiac branch of the sympathetic, whilst it 

 receives a communicating branch from the superior cervical ganglion of 

 the sympathetic. 



Nervus Recurrens. The recurrent nerve arises differ- 

 ently on the two sides. On the right side, after springing 

 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 from the vagus, 



