100 HUMAN PHYSIOLOGY. 



Properties. Irritation of the roots at their origin calls forth evidences 

 of pain ; it is, therefore, a sensory nerve, but its sensibility is not so acute 

 as that of the trifacial. Irritation of the trunk after its exit from the 

 cranium produces contraction of the muscles of the palate and pharynx, 

 due to the presence of anastomosing motor fibres. 



Division of the nerve abolishes sensibility in the structures to which it is 

 distributed, and impairs the sense of taste in the posterior third of the 

 tongue (see Sense of Taste). 



Function. Governs sensibility of pharynx, presides partly over the 

 sense of taste, and controls reflex movements of deglutition and vomiting. 



loth Pair. Pneumogastric. Par Vagum 



Apparent Origin. From the lateral side of the medulla oblongata, 

 just behind the olivary body. 



Deep Origin. In the gray nuclei in the lower half of the floor of the 

 4th ventricle, and in the substance of the restiform body. Some' filaments 

 are traced along the restiform tract, toward the cerebellum, and others to 

 the median line of the floor of the 4th ventricle, where many of them 

 decussate. 



This nerve has two ganglia ; one in the jugular foramen, called the gan- 

 glion of the root, and another outside of the cranial cavity on the trunk, 

 the ganglion of the trunk. 



Distribution. The filaments from the root unite to form a single trunk, 

 which leaves the cavity of the cranium, through the jugular foramen, in 

 company with the spinal accessory and glosso-pharyngeal. It soon receives 

 an anastomotic branch from the spinal accessory, and afterward branches 

 from the facial, the hypoglossal and the anterior branches of the two upper 

 cervical nerves. 



As the nerve passes down the neck it sends off the following main 

 branches : 



1. Pharyngeal nerves, which assist in forming the pharyngeal plexus, 

 which is distributed to the mucous membrane and muscles of the pharynx. 



2. Superior laryngeal nerve, which enters the larynx through the thyro- 

 hyoid membrane, and is distributed to the mucous membrane lining the 

 interior of the larynx, and to the crico-thyroid muscle and the inferior con- 

 strictor of the pharynx. The " depressor nerve" found in the rabbit, is 

 formed by the union of two branches, one from the superior laryngeal, the 

 other from the main trunk; it passes downward to be distributed to the 

 heart. r < - , - - - : f 



