GLOSSO-PHARYNGEAL NERVE 7G7 



Tilt' anterior or upijcr branch consists entirely of vestil)ular libres, it divides 

 into three parts which pass above the crista falciforniis, through the area cril)rosa 

 superior, and are distributed to the utricle, and to the ampullae of the sui)erior and 

 external semicircular canals. Cianglionic nerve-cells are found in this part of the 

 nerve. 



The lower or posterit)r branch contains l)Oth vestil)ular and cochlear iil)res. It 

 trives oft' the former in two twigs which contain ganglion ci-lls, one passes through 

 the area cribrosa media to the saccule, and the other through the foramen singulare 

 to the am}>ulla of the ))osterior vertical semicircular canal. The remaining and 

 larger ])art of the lower branch consists of cochlear libres which pass through the 

 tractus si)iralis foraminulentus of the inferior cribriform area into the central 

 canal of the modilus and the spiral lamina of the cochlea. They are connected 

 with the nerve-cells of the spiral ganglion of the cochlea, and they terminate 

 in the or^an of Corti. 



NINTH OR GLOSSO-PHARYNGEAL NERVE 



The glosso-pharyngeal nerve is made up of fibres derived from three different 

 sources. Two of these sets of fibres arise from distinct groups of cells, and 

 re})resent the motor part of the nerve and the portion devoted to the special sense 

 of taste. The third set of fibres takes the form of an ascending root (funiculus 

 solitarius)', the round cross-section of which forms a consi)icuous object in sections 

 through the lower part of the medulla. The fibres from these three sources emerge 

 in the form of several fasciculi (superficial origin) in the groove between the olivary 

 and restiform l^odies, near the lower border of the pons, in series with the roots of 

 the vagus nerve. 



The two principal nuclei are called the small-celled and the large-celled nuclei, 

 and are absolutely continuous with the nuclei of the vagus and of the accessory 

 part of the spinal accessory nerve. 



The small-celled nucleus (sensory, or accessorio-vago-glosso-pharyngeal 

 nucleus) i-orresponds for the most part to the ala cinerea in the floor of the fourth 

 ventricle. In this situation it lies immediately external to the chief nucleus of the 

 hypo-glossal nerve. Higher up, it recedes from the middle line, and is more dee]>ly 

 ))lace(l, being covered by the chief nucleus of the auditory nerve. It is from this 

 d(H'i)er (up])er) ))art that the glosso-pharyngeal fil)res take origin and these fibres 

 are regarded as the conductors of the s])ecial sense of taste. 



The large-celled nucleus (motor nucleus, nucleus aml)igvuis) contains ci'lls 

 resembling the motor cells in the anterior horn of the sjnnal cord, and is regarded 

 as a portion of the head of that horn which has been ami)Utated from the neck l)y 

 the decussation of the pyramids. * It is more deeply placed than the small-celled 

 nucleus. It is i)laced between the nucleus lateralis and external accessory olive, and 

 somewhat dorsally to both. It extends in a sagittal direction from the level of the 

 stria,' medullares downwards to a point a little below the fourth ventricle. From 

 the upper end of this nucleus fi'bres j)ass dorsally and then arch outwards to join 

 the fibres derived from the small-celled nucleus. Both sets of fibres then ])rocee(I 

 forwards and outwards, piercing the ascending root of the trigeminal, and emerge 

 at the ventral margin of the restiform body. 



The ascending root (funiculus solitarius) commences at a i)oint innuediately 

 above the level of the decussation of the pyramids. It ])asses u}nvards in the form 

 of a shar])ly circumscribed round bundle, gaining in strength as it ascends. It is 

 placed at first close to the outer side of the nucleus of the hypoglossal nerve; 

 higher up it is related to the outer side of the small-celled (accessorio-vago-glosso- 

 l)haryngeal) nucleus (fig. 4?>\), and lies dorsally to the roots of the vagus. Finally, 

 at the level of the stria? medullares, it lu-nds at right angles to its former course, and 

 runs forwards and outwards, traversing thi' sul)stantia gelatinosa and the ascending 

 root of the trigeminal to join the rest of the glosso-pharyngeal nerve, forming the 

 uppermost (most ])roximal) of the series of fasciculi which has been descri])ed as 

 the superficial origin of that nerve. 



