1496 A MANUAL OF ANATOMY 



the spinal cord. The nucleus ambiguus is ventral in position to 

 the dorsal vago-glosso-pharyngeal nucleus, and the axons of its 

 cells, some of which form the glosso-pharyngeal efferent or motor 

 fibres, pass dorsalwards towards the more superficially placed dorsal 

 vago-glosso-pharyngeal nucleus. They then alter their course and 

 pass ventralwards and outwards, and associate themselves with 

 the afferent or sensory glosso-pharyngeal fibres. 



The tuniculi of the glosso-pharyngeal nerve appear in the dorso- 

 lateral sulcus of the medulla oblongata, between the olivary and 

 restiform bodies, and immediately below the facial nerve. 



Distribution. — ^The glosso-pharyngeal nerve is distributed to 

 (i) the mucous membrane of the posterior third of the tongue, of 

 which part it is the nerve of taste, as well as of common sensation ; 

 (2) the mucous membrane of the pharynx, tonsil, and fauces ; (3) the 

 mucous membrane of the tympanum ; and {4) the stylo-pharyngeus 

 muscle. It also furnishes secretory and vaso-dilator fibres to the 

 parotid gland through means of (i) its tympanic branch (Jacobson's 

 nerve), (2) the tympanic plexus, (3) the small superficial petrosal 

 nerve, (4) the otic ganglion, and (5) the auriculo-temporal nerve. 



Tenth, Pneumogastric, or Vagus Nerve. — ^This nerve consists of 

 afferent or sensory fibres, which grow into the medulla oblongata; 

 and efferent or motor fibres, which arise within the medulla 

 oblongata . 



Afferent or Sensory Fibres. — ^These fibres arise from the central 

 poles of the bipolar cells of the ganglion of the root and the ganglion 

 of the trunk of the nerve, which resemble the glosso-pharyngeal 

 ganglia (jugular and petrous), the Gasserian ganglion of the fifth 

 nerve, and the spinal ganglia. Having entered the medulla oblon- 

 gata, the afferent fibres pass to the same two terminal sensory 

 nuclei as do the afferent fibres of the glosso-pharyngeal nerve — 

 namely, the dorsal vago-glosso-pharyngeal nucleus and the nucleus 

 of the fasciculus solitarius — which have just been described in con- 

 nection with the glosso-pharyngeal nerve. The most of the afferent 

 fibres of the vagus nerve pass to the vagal portion of the dorsal vago- 

 glosso-pharyngeal nucleus, which represents its greater and lower 

 part, the highest part of the nucleus receiving, as stated, a few of 

 the afferent fibres of the glosso-pharyngeal nerve. Within the 

 vagal part of the nucleus the afferent fibres of the vagus terminate 

 in arborizations around its cells. A few of the afferent fibres, 

 however, descend along with most of the afferent fibres of the glosso- 

 pharyngeal nerve, the two sets of descending fibres constituting the 

 strand called the fasciculus solitarius, already described in connec- 

 tion with the glosso-pharyngeal nerve. These descending afferent 

 vagal fibres terminate, like the corresponding glosso-pharyngeal 

 fibres, in the nucleus of the fasciculus solitarius, which has been 

 described in connection with the glosso-pharyngeal nerve. 



The dorsal vago-glosso-pharyngeal sensory nucleus, and the 

 nucleus of the fasciculus solitarius, also sensory, are therefore 

 shared in common by the afferent or sensory fibres of the glosso- 



