1010 THE NERVE SYSTEM 



geal descends beneath the mucous membrane on the inner surface of the thyroid 

 cartilage, where the two nerves become united. 



The Inferior or Recurrent Laryngeal Branch of the Vagus (n. laryngeus inferior) 

 (Figs. 744 and 746), so called from its reflected course, is the motor nerve of the 

 larynx. It arises, on the right side, in front of the subclavian artery; winds from 

 before backward around that vessel, and ascends obliquely to the side of the trachea 

 behind the common carotid artery, and either in front of or behind the inferior 

 thyroid artery. On the left side it arises m front of the arch of the aorta, and 

 winds from before backward around the aorta at the point where the impervious 

 ductus arteriosus is attached, and then ascends to the side of the trachea. The 

 nerve on each side ascends in the groove between the trachea and oesophagus, 

 and, passing under the lower border of the Inferior constrictor muscle, enters the 

 larynx behind the articulation of the inferior cornu of the thyroid cartilage with 

 the cricoid, being distributed to all the muscles of the larynx except the Crico- 

 thyroid. It communicates with the superior laryngeal nerve and gives off a 

 few filaments to the mucous membrane of the lower part of the larynx. 



The recurrent laryngeal, as it winds around the subclavian artery and aorta, 

 gives off several cardiac filaments, which unite with the cardiac branches from 

 the vagus and sympathetic. As it ascends in the neck it gives off oesophageal 

 branches, more numerous on the left than on the right side, which supply the 

 mucous membrane and muscular coat of the oesophagus; tracheal branches to 

 the mucous membrane and muscular fibres of the trachea; and some pharyngeal 

 filaments to the Inferior constrictor of the pharynx. 



The Cervical Cardiac Branches (rami cardiaci superiores), two or three in number, 

 arise from the vagus, at the upper and lower parts of the neck. 



The superior branches are small, and communicate with the cardiac branches 

 of the sympathetic. They can be traced to the great or deep cardiac plexus. 



The inferior branches, one on each side, arise at the lower part of the neck, 

 just above the first rib. That from the right vagus passes ventrad or by the 

 side of the innominate artery, and communicates with one of the cardiac nerves 

 proceeding to the great or deep cardiac plexus; that from the left runs across the 

 left side of the arch of the aorta and joins the superficial cardiac plexus. 



The Thoracic Cardiac Branches (rami cardiaci inferiores), on the right side, 

 arise from the trunk of the vagus as it lies by the side of the trachea, and from its 

 recurrent laryngeal branch, but on the left side from the recurrent nerve only; 

 passing inward, they terminate in the deep cardiac plexus. 



The Anterior or Ventral Pulmonary Branches, two or three in number, and of 

 small size, are distributed on the anterior aspect of the root of the lungs. They 

 join with filaments from the sympathetic, and form the anterior pulmonary plexus 

 (plexus pulmonalis anterior}. 



The Posterior or Dorsal Pulmonary Branches, more numerous and larger than 

 the anterior, are distributed on the posterior aspect of the root of the lung; they 

 are joined by filaments from the third and fourth (sometimes also from the first 

 and second) thoracic ganglia of the sympathetic, and form the posterior pulmonary 

 plexus (plexus pulmonalis posterior}. Branches from both plexuses accompany 

 the ramifications of the bronchi through the substance of the lungs (rami bronchiales 

 anteriores and rami bronchiales posteriores}. 



The CEsophageal Branches (rami oesophagei) are given off from the vagus both 

 above and below the pulmonary branches. The lower are more numerous and 

 larger than the upper. They form, together with branches from the opposite 

 nerve, the oasophageal plexus. From this plexus branches are distributed to the 

 back of the pericardium. 



The Gastric Branches (rami gastrici) (Fig. 744) are the terminal filaments of 

 the vagus nerve. The nerve on the right side is distributed to the posterior 



