i2 7 2 HUMAN ANATOMY. 



a. The cardiac branches (rr. cardiad inferiores) are given off in the superior mediastinum 

 and enter the deep cardiac plexus. 



b and c. Tracheal and cesophageal branches (rr. tracheales et oesophagei) are given off as 

 the nerve ascends in the neck between the trachea and oesophagus. 



d. Muscular branches enter the inferior constrictor of the pharynx. 



e. The terminal branches (n. laryngeus inferior) are formed at the point where the nerve 

 breaks up on the inner side of the thyroid cartilage. They supply the intrinsic muscles of the 

 larynx, with the exception of the crico-thyroid. 



As it turns to ascend, the inferior laryngeal nerve communicates with the inferior cervical 

 ganglion of the sympathetic, its terminal filaments joining with those of the internal laryngeal. 



Variations. The inferior laryngeal nerve has been seen to supply twigs to the crico-thyroid 

 muscle. In cases in which the subclavian artery arises dorsally, the right recurrent 

 laryngeal passes directly downward and inward from the vagus to the larynx. 



8. The thoracic cardiac nerves (rr. cardiac! inferiores) of the right side are 

 derived both from the vagus as it lies beside the trachea and from the inferior laryn- 

 geal. Those of the left side arise exclusively from the inferior laryngeal. They 

 help to form the deep cardiac plexus. 



9. The anterior pulmonary branches (rr. bronchiales anteriores) are two 

 or three small filaments which, on the right side, receive communicating fibres from 

 the deep cardiac plexus and, on the left side, are joined by filaments from both car- 

 diac plexuses. These unite to form the anterior pulmonary plexuses (plexus 

 pulmonales anteriores) (Fig. 1080), which communicate with each other and with the 

 posterior plexuses, and ramify over and supply the anterior aspect of the bronchus 

 and root of the lung. 



10. The posterior pulmonary branches (rr. bronchiales posteriores) are 

 several large twigs which join with filaments from the second, third and fourth tho- 

 racic ganglia of the sympathetic to form the posterior pulmonary plexus (plexus 

 pulmonalis posterior). Fibres from this plexus communicate with the corresponding 

 structure of the opposite side and with the anterior pulmonary plexuses, in this way each 

 vagus sending fibres to both lungs. Branches from the plexus, bearing tiny ganglia, 

 follow the subdivisions of the bronchi to supply the ultimate units of the lung. 



n. The cesophageal branches (rr. oesophagei) are given off in two situa- 

 tions : in the superior mediastinum, where the right vagus and the left inferior 

 laryngeal distribute cesophageal branches, and in the posterior mediastinum, where 

 the oesophagus is surrounded by branches from the cesophageal plexus or plexus 

 gul<z (Fig. 1081). This plexus is composed of the two vagus nerves, after they 

 leave the posterior aspect of the bronchi, in conjunction with filaments from the 

 great splanchnic nerves and from some of the lower thoracic ganglia. Both the 

 muscular and mucous coats of the oesophagus are innervated from this source. 



12. The pericardial branches (rr. pericardiaci) are given off to the upper 

 anterior portion of that membrane by either vagus and to the posterior portion by 

 the cesophageal and frequently the posterior pulmonary plexuses. 



13. The abdominal branches come from both nerves. On gaining the pos- 

 terior surface of the stomach after following the corresponding aspect of the oesopha- 

 gus, the right vagus forms the posterior gastric plexus along the lesser curvature, 

 from which gastric branches supply the posterior surface of the stomach ; the 

 remaining and larger part of the plexus is continued as the cocliac branches to 

 the plexus of the same name and, thence, in company with the sympathetic strands, 

 to the subsidiary plexuses supplying the spleen, the pancreas, the intestine, the 

 suprarenal bodies and the kidneys. In a similar manner, along the lesser curvature 

 the left vagus forms the anterior gastric plexus, from which numerous gastric 

 branches are distributed to the anterior surface of the stomach, the continuation of 

 the plexus being hepatic branches, which join the sympathetic filaments accompany- 

 ing the hepatic artery to supply the liver. 



Practical Considerations. The pneumogastric nerve may be compressed 

 or displaced by tumors in the neck, or it may be injured in accidental or operative 

 wounds, or by fracture of the base of the skull. Its division is not always fatal ; in 



