THE VAGUS NERVE 807 



oesophageus dorsalis, ventralis) . These run backward in the posterior mediastinum, 

 dorsal and ventral to the oesophagus respectively, and enter the abdominal cavity 

 through the hiatus oesophageus; they supply branches to the oesophagus and 

 anastomose with each other. The dorsal trunk receives the major part of its fibers 

 from the right vagus. After entering the abdomen it passes to the left of the 

 cardia, and divides into gastric and coeliac branches; the former gives branches to 

 the visceral surface of the stomach, forming the posterior gastric plexus; the latter 

 ends in the right cceliaco-mesenteric ganglion and the anterior interganglionic cord. 

 The smaller ventral trunk passes to the lesser curvature of the stomach and ramifies 

 on the parietal surface of the stomach; it forms here the anterior gastric plexus 

 from which branches are supplied also to the first part of the duodenum and to the 

 liver and pancreas.^ 



The collateral branches of the vagus are as follows : 

 v.- 1. The pharyngeal branch (R. pharyngeus) is given off in relation to the 

 anterior cervical ganglion, turns around the internal carotid artery, and runs 

 ventrally and forward on the guttural pouch to the dorsal wall of the pharynx 

 (Fig. 562). Here its branches concur with the pharyngeal branch of the glosso- 

 pharyngeal nerve and with filaments from the spinal accessory and the sympathetic 

 in forming the pharyngeal plexus. This supplies the muscles of the pharynx and 

 of the soft palate (except the tensor palati), delicate filaments to the anterior 

 cervical ganglion of the sympathetic, and a larger branch which passes along the 

 side of the oesophagus and ramifies in its cervical part. 



According to EUenberger and Baum, the pharjoigeal plexus receives filaments also from the 

 digastric, anterior laryngeal, hypoglossal, and first cervical nerves. The branches of the plexus 

 form secondary intermuscular and submucous plexuses, in which there are numerous minute 

 ganglia. 



2. The anterior (or superior) laryngeal nerve (N. laryngeus cranialis) is larger 

 than the preceding and arises a little behind it (Fig. 562). It crosses the deep face 

 of the origin of the external carotid artery, runs downward and forward over the 

 lateral wall of the pharj^nx behind the hypoglossal nerve, and passes through the 

 foramen below the anterior cornu of the thyroid cartilage. Its terminal branches 

 ramify in the mucous membrane of the larynx, the floor of the pharynx, and the 

 entrance to the oesophagus; they anastomose with those of the recurrent. At 

 its origin the nerve gives off its small external branch (R. extemus) ; this descends 

 to the crico-thyroid muscle, which it supplies, and sends filaments to the crico- 

 pharyngeus also. It often arises from the vagus just below the anterior laryngeal 

 and may come from the pharyngeal branch. 



At the point of origin of the anterior laryngeal nerve there is a plexiform widening which is 

 regarded by some authors as the homologue of the ganglion nodosum of man; it often contains 

 nmiute gangha. From it a filament arises which, after a short course, rejoins the vagus or enters 

 the sympathetic trunk. Stimulation of its central end causes a reduction of the blood-pressure, 

 and it is therefore termed the depressor nerve (N. depressor). On reaching the heart it passes 

 between the aorta and the pulmonary artery and is distributed to the myocardium. 



''•■y 3. The recurrent nerve (N. recurrens), also termed the inferior or posterior 

 laryngeal nerve, difl^ers on the two sides in its point of origin and in the first part of 

 its course. The right nerve (Fig. 554) is given off opposite the second rib, turns 

 around the dorso-cervical artery from without inward, runs forward on the ventral 

 part of the lateral surface of the trachea, and ascends in the neck on the ventral 

 face of the common carotid artery. The left nerve (Fig. 553) arises from the vagus 

 where the latter begins to cross the aortic arch. It passes back over the ligamentum 

 arteriosum, winds around the concavity of the aortic arch from without inward, 



1 It will be noted that the formation of the ventral cBsophageal trunk usually occurs at the 

 root of the lungs, while the union of the dorsal branches of the two vagi generally occurs nearer the 

 hiatus oesophageus. 



