THE THOEACIC PLEXUSES. 789 



supplies cardiac branches and (on the right side) the recurrent (laryngeal) 

 nerve (Fig. 661). 



Kami Cardiaci Superiores. The cardiac branches are superior and inferior. 

 On the right side both cardiac branches pass downwards into the thorax behind the 

 subclavian artery, and proceed alongside the trachea to join the deep cardiac plexus. 

 On the left side the two nerves separate on reaching the thorax. The superior 

 nerve passes deeply alongside the trachea to join the deep cardiac plexus. The 

 inferior nerve accompanies the vagus nerve over the aortic arch, along with the 

 superior cervical cardiac branch of the sympathetic, to end in the superficial 

 cardiac plexus. 



N. Eecurrens. The right recurrent (laryngeal) .nerve arises at the root of 

 the neck, as the vagus crosses in front of the first part of the subclavian artery. 

 It hooks round the artery, and passes obliquely upwards and medially behind the 

 subclavian, the common carotid, and the inferior thyreoid arteries and the thyreoid 

 gland. It finally disappears beneath the inferior border of the inferior constrictor 

 muscle, and, receiving the name of inferior laryngeal nerve, it ends in supplying the 

 muscles of the larynx. In its course it gives off the following branches : 



(1) Cardiac branches (rami cardiaci inferiores) arise as the nerve winds round the 

 subclavian artery, and course downwards alongside the trachea to end in the deep 

 cardiac plexus. 



(2) Communicating branches to the inferior cervical ganglion of the sympathetic 

 arise from the nerve behind the subclavian artery. 



(3) Muscular branches supply the trachea, oesophagus (rami tracheales et 

 cesophagei), and the inferior constrictor of the pharynx. 



(4) Terminal branches supply the muscles of the larynx (except the crico- thyreoid) 

 and communicate beneath the lamina of the thyreoid cartilage with branches of 

 the internal laryngeal nerve. 



Branches of the Vagus in the Thorax. In the thorax the vagi form the 

 great pulmonary and oesophageal plexuses. The right nerve, in addition, furnishes 

 , cardiac branches ; and the left nerve gives off the recurrent (laryngeal) nerve. 



N. Recurrens. The left recurrent (laryngeal) nerve differs from the nerve 

 of the right side mainly in its point of origin and in the early part of its course. 

 It springs from the vagus as it crosses the aortic arch, and, after hooking round the 

 arch, lateral to the ligamentum arteriosum, it passes upwards in the superior medi- 

 astinum, in the interval between the trachea and oesophagus, to the neck. In the 

 , neck its course and relations are similar to those of the nerve of the right side. 

 The branches of the nerve are the same as those of the right nerve. The cardiac 

 branches are larger, and, arising below the aortic arch, proceed to the deep cardiac 

 plexus. 



Cardiac branches from the right vagus nerve arise in the superior mediastinum, 



and pass downwards alongside the trachea to join the deep cardiac plexus. On 



the right side thoracic cardiac branches are thus supplied from both the trunk of 



the nerve and its recurrent branch ; on the left side the cardiac branches in the 



, thorax arise solely from the recurrent branch. 



Abdominal Branches. After the formation of the oesophageal plexus the 

 two vagi nerves resume their course, and passing along with the gullet through 

 the diaphragm, terminate by supplying the stomach. The right nerve enters 

 the abdominal cavity behind the gullet, and is distributed to the posterior 

 surface of the stomach. It sends communicating offsets to the cceliac, splenic, and 

 renal plexuses. The left nerve applies itself to the anterior surface and small cur- 

 vature of the stomach, to which it is distributed. It sends communicating offsets 

 along the small curvature of the stomach to the right vagus, and between the 

 1 layers of the gastro-hepatic ligament to the hepatic plexus. 



PLEXUS THORACALES. 



Plexus Cardiaci. The cardiac branches of the vagus nerve (both cervical 

 md thoracic) combine with the cardiac branches of the sympathetic to form the 

 .superficial and deep cardiac plexuses. 



515 



