THE CRANIAL NERVES. 601 



1. The pharyngeal nerves, which, after entering into the formation of the 



pharyngeal plexus, are distributed to the mucous membrane and to the 

 muscles of the pharynx ; e.g. , superior and inferior constrictors, the levator 

 palati, and the azygos uvulae; according to B eevor and Horsley the nerves 

 for these muscles are branches of the spinal accessory. 



2. The esophageal nerves, which after entering into the formation of the 



esophageal plexus, are distributed to the mucous membrane, and to the 

 muscles of the lower two-thirds of the esophagus. 



3. The superior laryngeal nerve which, entering the larynx through the 



thyro-hyoid membrane, is distributed to the mucous membrane lining 

 the interior of the larynx and to the crico-thyroid muscle. From the 

 superior laryngeal and the main trunk small branches are given off 

 which in the rabbit unite to form a single nerve, the so-called depressor 

 nerve. (See page 375.) It is distributed to the surface of the ventricle 

 and perhaps to structures at the root of the aorta. Though this 

 anatomic arrangement is not found in man, there are many reasons for 

 believing that analogous fibers are present in the vagus trunk of man and 

 other animals. 



4. The inferior laryngeal nerve which is distributed utimately to all the 



muscles of the larynx (except the crico-thyroid) and to the inferior con- 

 strictor of the pharynx. These motor fibers are derived from the spinal 

 accessory. 



5. The cardiac nerves which, after entering into the formation of the cardiac 



plexus, are distributed to the heart. 



6. The pulmonic nerves distributed to the mucous membrane of the bronchial 



tubes and their ultimate terminations, the lobules and air-cells, as well 

 as to their non-striated muscle-fibers. 



7. The gastric and intestinal nerves, distributed to the mucous membrane and 



muscle walls of the stomach, intestines, and gall-bladder. Other fibers 

 in all probability pass to the liver, spleen, kidney, and suprarenal bodies. 



Properties of the Pneumogastric or Vagus Nerve and its Various 

 Branches. Faradization of the vagus nerve close to the medulla oblongata 

 gives rise to sensations of pain and to contraction of the musculature of a 

 portion of the alimentary tract, viz. : the esophagus, stomach, and possibly 

 of the intestine and of the pulmonary apparatus. Division of the nerve is 

 followed by a loss of sensibility in the mucous membrane of the alimentary 

 tract and of the pulmonary apparatus, together with a loss of motility of 

 the structures above mentioned. 



Stimulation of the trunk of the nerve in different parts of its course pro- 

 duces a variety of results dependent to some extent on the presence of anas- 

 tomosing branches from adjoining nerves. 



The Pharyngeal Nerves. Faradization of the pharyngeal nerves consisting 

 of both afferent and efferent fibers, gives rise to sensations of pain, contraction 

 of the pharyngeal muscles, and perhaps to vomiting. Division of these nerves 

 is followed by a loss of sensibility in the parts to which they are distributed and 

 by paralysis of the muscles with a consequent impairment of deglutition. 



The Esophageal Nerves. Faradization of the esophageal nerves, gives 

 rise to sensations of pain and to contractions of the muscle coat of the esoph- 

 agus. Division of these nerves is followed by a loss of sensibility in the parts 



