636 TEXT-BOOK OF PHYSIOLOGY 



nerve. (See page 325.) 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 ultimately 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, and at the same time causes 

 an inhibition of the heart. Division of the nerve is followed by a loss of 

 sensibility in the mucous membrane of the alimentary tract and of the pul- 

 monary apparatus, together with a loss of motility of the structures above 

 mentioned, and a loss of the inhibition .of the heart. 



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 esopha- 

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

 to which they are distributed, a partial paralysis of the muscle coat and an 

 impairment of deglutition. 



The Superior Laryngeal Nerve. Faradization of the superior laryngeal 

 nerve gives rise to sensations of pain, and to contraction of the crico-thyroid 

 muscle. Through reflected impulses it causes contraction of the muscles 

 of deglutition, and of the muscles concerned in the act of coughing; inhibi- 

 tion of the inspiratory movement and arrest of respiration in the condition 

 of expiratory standstill, with perhaps a tetanic contraction of the expiratory 

 muscles, and contraction of the laryngeal muscles with closure of the glottis. 



Peripheral stimulation of this nerve e.g., the contact of foreign 

 particles gives rise to a similar series of phenomena. Division of these 

 nerves is followed by a loss of sensibility in the laryngeal mucous mem- 

 brane, paralysis of the crico-thyroid muscle with a consequent lowering of 



