630 CRANIAL NERVES. 



The filament to the Arytenoid muscle is distributed partly to it, and partly 

 to the mucous lining of the larynx. 



The filament which joins with the recurrent laryngeal, descends beneath the 

 mucous membrane on the posterior surface of the larynx, behind the lateral 

 part of the thyroid cartilage, where the two nerves become united. 



The inferior or recurrent laryngeal, so called from its reflected course, is the 

 motor nerve of the larynx. It arises on the right side, in front of the sub- 

 clavian artery: winds from before backwards round that vessel, and ascends 

 obliquely to the side of the trachea, behind the common carotid and inferior 

 thyroid arteries. On the left side, it arises in front of the arch of the aorta, 

 and winds from before backwards round the aorta at the point where the 

 obliterated remains of the ductus arteriosus are connected with it, and then 

 ascends to the side of the trachea. The nerves on both sides ascend in the 

 groove between the trachea and oesophagus, and, passing under the lower 

 border of the Inferior Constrictor muscle, enter the larynx behind the articu- 

 lation of the inferior cornu of the thyroid cartilage with the cricoid, being 

 distributed to all the muscles of the larynx, excepting the Crico-thyroid, and 

 joining with the superior laryngeal. 



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

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

 pneumogastric and sympathetic. As it ascends in the neck, it gives off' ceso- 

 phageal 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, two or three in number, arise from the pneumo- 

 gastric, at the upper and lower part of the neck. 



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

 of the sympathetic, and with the great cardiac plexus. 



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

 neck, just above the first rib. On the right side, this branch passes in front 

 of the arteria innominata, and anastomoses with the superior cardiac nerve. 

 On the left side, it passes in front of the arch of the aorta, and anastomoses 

 either with the superior cardiac nerve, or with the cardiac plexus. 



The thoracic cardiac branches, on the right side, arise from the trunk of the 

 pneumogastric, as it lies by the side of the trachea: passing inwards, thev 

 terminate in the deep cardiac plexus. On the left side, they arise from the left 

 recurrent laryngeal nerve. 



The anterior 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. 



The posterior pulmonary branches, more numerous and larger than the ante- 

 rior, are distributed on the posterior aspect of the root of the lung: they are 

 joined by filaments from the third and fourth thoracic ganglia of the sympa- 

 thetic, and form the posterior pulmonary plexus. Branches from both plexuses 

 accompany the ramifications of the air-tubes through the substance of the lungs. 



The cesophageal branches are given off from the pneumogastric both above and 

 below the pulmonary branches. The latter are the more numerous and largest. 

 They form, together with branches from the opposite nerve, the cesophageal 

 plexus. 



The gastric branches are the terminal filaments of the pneumogastric nerve. 

 The nerve on the right side is distributed to the posterior surface of the 

 stomach, and joins the left side of the coeliac plexus, and the splenic plexus. 

 The nerve on the left side is distributed over the anterior surface of the 

 stomach, some filaments passing across the great cul-de-sac, and others along the 

 lesser curvature. They unite with branches of the right nerve and sympathetic, 

 some filaments passing through the lesser omentum to the left hepatic plexus. 



