92 THE NERVOUS SYSTEM 



solitarius, an elongated column of grey matter (Fig. 47) which 

 also receives some of the sensory fibres of the vagus. 



The glosso-pharyngeal nerve leaves the medulla oblongata at 

 the upper end of the groove between the olive and the restiform 

 body (Fig. 8), and passes out of the skull through the jugular 

 foramen in company with the vagus and accessory nerves. In 

 its extracranial course the nerve is very deeply situated, and 

 it inclines downwards and medially in the neck to reach the 

 lateral wall of the pharynx. 



Two ganglia, termed the ganglion superius and the ganglion 

 petrosum^ are found on the nerve as it lies in the jugular 

 foramen. 



The tympanic branch arises from the petrosal ganglion and, 

 passing through a minute canal in the petrous temporal, enters 

 the middle ear, where it breaks up into a small plexus. A 

 branch emerges from this plexus and unites with a small 

 branch from the geniculate ganglion of the facial to form the 

 lesser superficial petrosal nerve, which ends in the otic ganglion 

 (p. 70). In this way the glosso-pharyngeal nerve establishes 

 communications with both the mandibular and the facial 

 nerves. 



It is said that the secretory fibres for the parotid gland leave 

 the glosso-pharyngeal in the tympanic branch and travel in the 

 lesser superficial petrosal nerve to the otic ganglion, from 

 which they pass directly to the auriculo-temporal nerve (p. 74). 



On the lateral wall of the pharynx the glosso-pharyngeal 

 nerve breaks up into lingual and pharyngeal branches. The 

 lingual branches supply the mucous membrane of the posterior 

 third of the tongue with ordinary sensation and with the sense 

 of taste, and they extend to the soft palate and the palatine 

 tonsil. In nuclear lesions of the tractus solitarius the sense of 

 taste is not lost over the posterior part of the tongue. On 

 account of the size of the tractus. solitarius the results of lesions 

 are very variable, but the escape of the taste fibres in such 

 lesions has led many authorities to the view that these fibres 

 pass to the sensory nucleus of the trigeminal, via the tympanic 



