THE CRANIAL NERVES. 553 



they arise into anatomic and physiologic connection with a portion of 

 the musculature of the alimentary canal and its diverticulum, the 

 lung. 



Communicating Branches. At or near the ganglia of the vagus 

 it receives communicating branches from the eleventh nerve, the 

 spinal accessory, the facial, the hypoglossal, and the anterior branches 

 of the two upper cervical nerves. Owing to this manifold origin of 

 the efferent fibers in the trunk and peripheral branches of the vagus, 

 it is, in some instances, difficult, if not impossible, to determine to 

 which of these nerves a given muscle contraction is to be referred. 



Vagal Branches. As the vagus passes down the neck it gives 

 off the following main branches (Fig. 255) : 



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



the pKaryngeal plexus, are distributed to the mucous membrane 

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

 constrictors, the tensor palati, levator palati, and the azygos 

 uvulae. 



2. The superior larynpeal nerve which, entering the larynx through 



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

 brane 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 unite to form a single nerve, the 

 so-called depressor nerve. It is distributed to the heart-muscle. 

 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. 



3. The inferinr faryu.ffp.al nerve which is distributed ultimatejjV^JjC^jill 



the muscles of the larynx except the crico-thyroid and to the 

 inferior constrictor of the pharynx. 



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



cardiac plexus, are distributed to the heart. 



5. The pulmonary nerves distributed to the mucous membrane of the 



bronchiaTfubes and their ultimate terminations, the lobules and 

 air-cells, as well as to their non-striated muscle-fibers. 



6. The gas tricand 'intestinal nerves, distributed to the mucous mem- 



brane and" muscular walls of the stomach and intestines. 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 

 palate, pharynx, 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 



