114 DISSECTION OF THE NECK. 



larynx. (See " LARYNX.") In the neck it furnishes branches to the 

 thyroid body, and the following offset to one laryngeal muscle and the 

 pharynx : 



The external laryngeal branch (fig. 25. 7 ) arises beneath the internal 

 carotid artery, and runs below the superior laryngeal nerve to the side of 

 the larynx. Here it gives offsets to the pharyngeal plexus, and it i* con- 

 tinued beneath the sterno-thyroideus to the crico-thyroid muscle ard the 

 inferior constrictor. Near its origin this branch communicates with the 

 superficial cardiac branch of the sympathetic* nerve. 



c. Cardiac branches. Some small cardiac nerves spring from the 

 pneumo-gastric at the upper part of the neck, and join cardiac branches 

 of the sympathetic. At the lower part of the neck, on each side, there is 

 a single cardiac nerve : the right one enters the chest and joins the deep 

 nerve.s_to the heart from the sympathetic ; and the left nerve terminates 

 in the superficial cardiac plexus of the thorax. 



d. The inferior laryngeal or recurrent nerve (fig. 25) leaves the pneumo- 

 gastric trunk on the right side opposite the subclavian artery, and winding 

 round that vessel, takes an upward course in the neck to the larynx, 

 ascending beneath the common carotid and inferior thyroid arteries, and 

 between the trachea and the oesophagus. At the larynx it enters beneath 

 the ala of the thyroid cartilage, where it will be afterwards traced. The 

 following branches arise from it : 



Some cardiac branches leave the nerve as it turns round the subclavian 

 artery ; these enter the thorax, and join the cardiac nerves of the sym- 

 pathetic. 



Muscular branches spring from it whilst it lies between the trachea and 

 the oesophagus, and are distributed to both those tubes. Near the larynx 

 some filaments are furnished to the inferior constrictor muscle. 



On the left side the recurrent nerve arises in the thorax, opposite the 

 arch of the aorta, but lies between the trachea and oesophagus in the 

 neck, as on the right side. 



The SPINAL ACCESSORY NERVE (fig. 26, 12 ) courses through the foramen 

 jugulare with the pneumo-gastric, but is not marked by any ganglion. 

 The nerve is constructed of two parts, viz., accessory to the vagus, and 

 spinal, which have a different origin and distribution. (Origin of the 

 cranial nerves.) 



The part accessory to the vagus (") is the smaller of the two, and finally 

 blends with the pneumo-gastric beyond the skull. In the foramen of exit 

 it lies close to the vagus, and joins the upper ganglion of that nerve by 

 one or two filaments. Below the foramen it is continued over the lower 

 ganglion of the nerve, and blends with the trunk beyond the ganglion. 

 It gives offsets to join the pharyngeal and upper laryngeal branches of the 

 pneumo-gastric, and according to Bendz, to many other branches of that 

 nerve. 



The spinal part (fig. 26, lz ) is much larger, is round and cord-like, and 

 is connected with the smaller piece whilst it is passing through the fora- 

 men jugulare. Beyond the foramen the nerve (fig. 25, 2 ) takes a back- 

 ward course through the sterno-mastoid muscle, and across the side of the 

 neck to end in the trapezius muscle : at first it is concealed by the jugular 

 vein, but it then passes either over or under that vessel. The connections 

 of the nerve beyond the sterno-mastoideus have been already examined 

 (p. 66). 



