728 THE NERVES. 



the internal pterygoid mtiscle. Lying beside the external maxillary 

 artery in the latter part of its course, it passes with it along the posterior 

 border of the large branch of the hyoid bone, and gains the base of the 

 tongue with the lingual artery, by coursing beneath the hyo-glossus brevis 

 muscle. The papilte on the posterior portion of the lingual mucus mem- 

 brane receive the terminal ramuscules of this nerve. (See the Sense of Taste.) 

 Collateral Branches. — On its course it furnishes : 



1. Jacobson's nerve (tympanic branch), a very thin filament springing from 

 Andersch's ganglion, proceeding upwards, and entering a particular foramen 

 in the tuberous portion of the temporal bone, to be distributed more 

 especially to the tympanum, sending also to the superficial petrous nerves 

 two branches which are designated the deep great and small petrous nerves. 



2. Filaments of communication with the superior cervical ganglion, two 

 or three in number, though sometimes replaced by a single ramuscule. 



3. A branch to the carotid plexus, which passes back on the guttural 

 pouch to reach the terminal extremity of the common carotid, whence its 

 filaments are sent, with those of the sympathetic nerve, either to the external 

 carotid, occipital, or even to the common carotid artery itself. This branch 

 communicates, by several anastomoses, with the numerous sympathetic 

 branches which pass from the superior cervical ganglion to the surface of 

 the guttural pouch, and which are either expended in that membrane, or 

 join the posterior border of the great hypoglossal nerve. 



4. A. pharyngeal branch (Fig. 342, 11), which is generally detached close 

 to the pharyngeal artery, and forms, along with the pharyngeal filaments of 

 the pneumogastric nerve, a remarkably intricate plexKs (pharyngeal) on the 

 upper wall of the pharynx, below the guttural pouch. This plexus receives 

 a filament from the hypoglossal nerve. 



10. Tenth Pair, Vagus, or Pneumogastric Nerves. (Figs. 338, 342, 362.) 



The pneumogastric nerve is as remarkable for its extent, as for the 

 multiplicity of physiological uses imposed upon it. 



It is prolonged to beyond the stomach, after distributing to that viscus, 

 the oesophagus, pharynx, lung, bronchi, trachea, and larynx a large number 

 of filaments on which depend the movements, secretory functions, and 

 purely sensory phenomena of which all these organs are the seat. 



Origin. — The pneumogastric is a mixed nerve, and consequently arises 

 from two kinds of roots ; these we will successively describe before passing 

 to its distribution, though it must be remarked that this subject has not yet 

 been fully determined. 



Sensitive roots. — These arise from a nucleus of grey substance situated 

 near the floor of the fourth ventricle, a little behind the glosso-pharyngeal 

 nucleus, and in which the fibres of the antero-lateral columns of the medulla 

 oblongata, or respiratory track of Bell, seem to be lost. In leaving the 

 medulla, they form from four to ten bundles, which describe a slight curve 

 whose convexity is upwards ; the highest median fibres correspond to the 

 groove that limits, superiorly, the respiratory tract, the posterior and ante- 

 rior fibres bending down to the pyramids— the second more than the first. 



These roots proceed transversely outwards, mixed with connective tissue 

 and some fine muscular ramifications, and leave the cranium by one of the 

 openings (jugular foramen) in the posterior foramen lacerum, uniting in 

 their passage through that aperture in a somewhat voluminous ganglion, 

 called in Man the jugular ganglion. 



