314 HEAD AND NECK 



below the base of the cranium. Strong branches of com- 

 munication pass between it and the first loop of the 

 cervical plexus, and the superior cervical ganglion of the 

 sympathetic. Further, the hypoglossal nerve is generally 

 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 anteriorly, 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. This, a much larger branch, 

 arises from the middle of the ganglion nodosum. It passes 

 downwards and anteriorly, but differs from the preceding 

 nerve by passing deep to the internal carotid artery. In 

 this situation it ends by dividing into the internal laryngeal 

 and external laryngeal nerves ; both of these have been 

 previously seen in the dissection of the anterior triangle 

 (p. 232). 



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 anteriorly to reach the crico-thyreoid 

 muscle, in which it ends. 



It supplies a few filaments to the inferior_'constrictor of the pharnyx 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 



