752 THE NERVOUS SYSTEM. 



nerve and gives off a few filaments to the mucous membrane of the lower part of 

 the larynx. 



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

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

 the pneumogastric and sympathetic. As it ascends in the neck it gives off cesoph- 

 ageal 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. 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. On the right side this branch passes in front or by the 

 side of the arteria innominata, and communicates with one of the cardiac nerves 

 proceeding to the great or deep cardiac plexus. On the left side it passes in front 

 of the arch of the aorta and joins the superficial 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, 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 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 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 first and second) thoracic 

 ganglia of the sympathetic, and form the posterior pulmonary plexus: Branches 

 from both plexuses accompany the ramification of the air-tubes through the sub- 

 stance of the lungs. 



The cesophageal branches are given off from the pneumogastric 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 

 cesophageal plexus or plexus gulce. From this plexus branches are distributed to 

 the back of the pericardium. 



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 with the sympathetic, some fila- 

 ments passing through the lesser omentum to the hepatic plexus. 



Surgical Anatomy. The laryngeal nerves are of considerable importance in considering 

 some of the morbid conditions of the larynx. When the peripheral terminations of the superior 

 laryngeal nerve are irritated by some foreign body passing over them, reflex spasm of the glottis 

 is the result. When the trunk of this same nerve is pressed upon by, for instance, a goitre or 

 an aneurism of the upper part of the carotid, we have a peculiar dry, brassy cough. When the 

 nerve is paralyzed, we have anaesthesia of the mucous membrane of the larynx, so that foreign 

 bodies can readily enter the cavity, and, in consequence of its supplying the crico-thyroid muscle, 

 the vocal cords cannot be made tense, and the voice is deep and hoarse. Paralysis of the 

 superior laryngeal nerves may be the result of bulbar paralysis, may be a sequel to diphtheria, 

 when both nerves are usually involved, or it may, though less commonly, be caused by the 

 pressure of tumors or aneurisms, when the paralysis is generally unilateral. Irritation of the 

 inferior laryngeal nerves produces spasm of the muscles of the larynx. When both these 

 recurrent nerves are paralyzed, the vocal cords are motionless, in the so-called "cadaveric posi- 

 tion " that is to say. in the position in which they are found in ordinary tranquil respiration 

 neither closed as in phonation, nor open as in deep inspiratory efforts. When one recurrent 

 nerve is paralyzed, the cord of the same side is motionless, while the opposite one crosses the 

 middle line to accommodate itself to the affected one ; hence phonation is present, but the voice 



