500 NEUEOLOGY. 



Its branches are the nerve of Jacobson, given off from the 

 petrosal ganglion, and distributed to the tympanum and its mem- 

 brane ; filaments to the superior cervical ganglion ; a branch to 

 the carotid plexus ; branches to the muscles of the pharynx; and 

 a communicating branch to the pneumogastric nerve. 



TENTH PAIR PAR VAGUM, OR PNEUMOGASTRIC. 



This is a mixed nerve, which originates by motor and sensory 

 roots. Its apparent origin is from a groove in the medulla ob- 

 longata, immediately behind the ninth nerve; its deep roots can 

 be traced to the restiform bodies, olivary fasciculi, and the grey 

 matter near the floor of the fourth ventricle. This nerve is 

 remarkable for its extent ; for the numerous dissimilar organs to 

 which it is distributed ; and for its free and extensive communi- 

 cation with other cerebro-spinal, and with the sympathetic nerves. 

 It pierces the dura mater in company with the eleventh nerve, and 

 passes through the foramen lacerum basis cranii, previously pre- 

 senting an oblong grey mass, the jugular ganglion. 



After leaving the cranium, the par vagum descends behind the 

 guttural pouch, close to the superior cervicular ganglion, crosses 

 to the inner side of the occipital artery, and joining the common 

 carotid, proceeds down the neck in the same sheath with that 

 artery. After entering the thorax, the course of the nerve on 

 either side varies. The right nerve, turning obliquely round the 

 brachial artery, proceeds backwards by the side of the trachea to 

 the origin of the bronchi, where it gains the under and right 

 side of the oasophagus ; while the left nerve passes along the 

 anterior aorta, crosses the origin of the posterior aorta, and gains 

 the upper and left side of the OBsophagus, the two being continued 

 to the stomach and the solar plexus. 



The branches of the par vagum are : 



1. A communicating branch to the facial near its origin. 



2. Numerous branches to the superior cervical ganglion. 



3. A sensory-motor branch to the pharynx, which communicates 

 with the pharyngeal branch of the ninth. 



4. The superior laryngeal, which passes to the sides of the 

 larynx, which it enters through a hole in the thyroid cartilage, 

 being distributed to the mucous membrane, and giving motor 

 fibres to some of the muscles of that organ. 



5. Filaments to the inferior cervical ganglion, two or three 



