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THE NERVE SYSTEM 



plexus gives off (1) the small superficial petrosal nerve (Fig. 740); (2) a branch 

 to join the great superficial petrosal nerve; and (3) branches to the tympanic 

 cavity, all of which will be described in connection with the anatomy of the ear. 



The Carotid Branches (n. caroticotympanicus superior and n. caroticotympanicus 

 inferior) descend along the trunk of the internal carotid artery as far as its com- 

 mencement, communicating with the pharyngeal branch of the vagus and with 

 branches of the sympathetic. 



The Pharyngeal Branches (rami pharyngei) are three or four filaments which 

 unite opposite the Middle constrictor of the pharynx with the pharyngeal branches 

 of the vagus and sympathetic nerves to form the pharyngeal plexus, branches 

 from which perforate the muscular coat of the pharynx to supply the muscles 

 and mucous membrane. 



The Muscular Branch (ramus stylopharyngeus) is distributed to the Stylo- 

 pharyngeus muscle. 



The Tonsillar Branches (rami tonsillares) supply the tonsil, forming a plexus 

 (circulus tonsillaris) around this body, from which branches are distributed to 

 the soft palate and fauces, where they communicate with the palatine nerves. 



The Lingual Branches (rami linguales) are two in number; one supplies the cir- 

 cumvallate papillae and the mucous membrane covering the surface of the base 

 of the tongue; the other perforates its substance, and supplies the mucous mem- 

 brane and follicular glands of the posterior one-third of the tongue and communi- 

 cates with the lingual nerve. 



The Gustatory Path. The impressions of taste reach the glossopharyngeal 

 nucleus in the medulla oblongata in two ways. From the posterior one-third 

 of the tongue and from the palate they reach the nucleus by the glossopharyngeal 

 nerve. From the anterior two-thirds of the tongue impulses of taste are conveyed 

 by the chorda tympani or portion of the nervus intermedius. From the glosso- 

 pharyngeal nucleus gustatory impressions pass by way of the medial fillet to the 

 thalamus of the opposite side, and from the thalamus through ventral thalamo- 

 cortical radiation to the gyrus hippocampi, where the cortical gustatory centre 

 is situated. 



Applied Anatomy. Injury may produce hemorrhage about the roots of the nerve. Berg- 

 mann reported such a case. The patient died from edema of the glottis after presenting evi- 

 dences of disorder of speech and difficulty in swallowing. Disease of the glossopharyngeal 

 nerve alone cannot usually be diagnosticated. 



THE TENTH, VAGUS, OR PNEUMOGASTRIC NERVE (N. VAGUS) 



(Figs. 743, 744). 



The tenth, vagus, or pneumogastric nerve has a more extensive distribution 

 than any of the other cranial nerves, passing through the neck and thorax to the 

 upper part of the abdomen. It is composed of both motor and sensor fibres. 

 It supplies the organs of voice and respiration with motor and sensor fibres, and 

 the pharynx, oesophagus, stomach, and heart with motor fibres. Its superficial 

 origin (Fig. 743) is by eight or ten filaments from the groove between the olive 

 and the restiform body below the glossopharyngeal; its central connections are 

 described on page 882. 



The real origin of the sensor fibres of the vagus is to be found in the cells of 

 the ganglia on the nerve viz., the ganglion of the root and the ganglion of the 

 trunk. The filaments become united and form a flat cord, which passes outward 

 beneath the flocculus to the Jugular foramen, through which it emerges from the 

 cranium (Fig. 744). In passing through this opening the vagus accompanies 

 the spinal accessory nerve, being contained in the same sheath of dura with it, a 



