THE VAGUS NERVE 807 
cesophageus dorsalis, ventralis). These run backward in the posterior mediastinum, 
dorsal and ventral to the cesophagus respectively, and enter the abdominal cavity 
through the hiatus cesophageus; they supply branches to the cesophagus 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 cceliac 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: 
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 cesophagus and ramifies in its cervical part. 
According to Ellenberger and Baum, the pharyngeal 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 pharynx 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 cesophagus; they anastomose with those of the recurrent. At 
its origin the nerve gives off its small external branch (R. externus); 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 
minute ganglia. 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. 
3. The recurrent nerve (N. recurrens), also termed the inferior or posterior 
laryngeal nerve, differs 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, 
1Tt will be noted that the formation of the ventral cesophageal 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 cesophageus. 
