THE CRANIAL NERVES. 141 



What is the function of the glosso-pharyngeal as a motor nerve ? 

 Whether by reason of its communications with other nerves or 

 not in its distribution, the nerve is a motor nerve as well as 

 sensory. Its distribution is to all the muscles of deglutition, 

 and stimulation causes contraction of the muscles, while division 

 paralyzes them. The very numerous connections of the nerve com- 

 plicate its anatomical origin very greatly, and interfere with a clear 

 comprehension of the unaided function of the nerve. 



Where does the reflex for swallowing originate? 



In the medulla oblongata, where the centre of origin of the nerve 

 is situated. 



What is the origin of the pneumogastric or tenth nerve ? 



It arises from the gray matter in the floor of the fourth ventri- 

 cle, its nucleus being very close to those of the glosso-pharyngeal, 

 spinal accessory, and hypoglossal. Its fibres pass through the sub- 

 stance of the medulla oblongata, and emerge from its lateral sur- 

 face with the roots of its associate nerves, the glosso-pharyngeal 

 and spinal accessory. It passes from the skull with them by the 

 jugular foramen. It has at this point a ganglionic enlargement. 

 From here it passes down the neck, and is distributed more diffusely 

 than any other cranial nerve. 



What synonyms has the tenth nerve ? 



Pneumogastric, from its distribution and function ; vagus or Par 

 Vagum, from its scattered distribution (vagus, Latin = wanderer). 



What principal distributions has the pneumogastric ? 



It is supplied to the organs by which air and food enter the body, 

 and besides this has several important connections with the sympa- 

 thetic system. (1) To the larynx it supplies sensation and motion 

 through the superior and inferior larytigeal branches. (2) In the 

 chest it forms the pulmonary plexuses, which innervate the bronchi 

 and lungs. (3) Branches to the cardiac plexus supply important 

 stimuli to the heart and great vessels. (4) There are branches to 

 the pliaryngeal and oesophageal plexuses which are both sensory and 

 motor, supplying both the mucous membrane and the muscular 

 structures of the parts. (5) Its terminal branches supply the sen- 

 sory and motor nerves to the stomach, the left nerve being dis- 

 tributed on its anterior wall, and the right posteriorly. (6) Branches 



