980 THE NERVOUS SYSTEM 



of bipolar cells, or cells which give off their central and peripheral processes directly 

 from opposite sides of the cell-body. The central fibres (axones) enter the medulla 

 oblongata. 



The peripheral fibres from the vestibular ganglion separate into an upper and a 

 lower branch. The upper or utriculo-ampullar branch divides into the following- 

 terminal branches: 



(1) The utricular branch passes through the superior macula cribrosa of the 

 vestibule and terminates in the macula acustica of the utriculus. 



(2) Accompanying the utricular branch through the superior macula cribrosa 

 is a branch, the superior ampullar, to the crista acustica of the ampulla of the supe- 

 rior semicircular canal, and 



(3) A similar branch, the lateral ampullar, to the ampulla of the lateral semi- 

 circular canal. 



The lower or sacculo-ampullar branch accompanies the cochlear division a short 

 distance further than the upper, and divides into 



(1) A branch, the posterior ampullar, which passes through the foramen singu- 

 lare and the inferior macula cribrosa and terminates in the ampulla of the posterior 

 semicircular canal, and 



(2) A branch, the saccular, which passes through the middle macula cribrosa 

 and terminates in the macula acustica of the sacculus. 



The central connections oj the vestibular division are described in detail on pages 805, 806. 

 Its large nucleus of termination, spread through the area acustica in the floor of the fourth 

 ventricle, and divided into four sub-nuclei, is associated with the nuclei fastigii, globosus, and 

 emboliformis of the cerebellum, with the nuclei of the eye-moving nerves, with the spinal cord, 

 and probably with the cerebral cortex. 



The cochlear division or nerve. The fibres of this division are distributed to 

 the organ of Corti in the cochlea, and so are considered as comprising the auditory 

 nerve proper. They arise from the long, coiled spiral ganglion of the cochlea, the 

 cells of which are likewise bipolar. The peripheral fibres of these cells (dendrites) are 

 shorter than those of the vestibular ganglion. They terminate about the auditory or 

 hair-cells of the organ of Corti and thus collect impulses aroused by stimuli affecting 

 these cells. The central fibres of the ganglion continue the central course through the 

 modiolar canal and the tractus spiralis foraminosus of the cochlea, and thence, 

 joining the vestibular division through the internal auditory meatus, they enter the 

 brain-stem to terminate in their dorsal and ventral nuclei. A description of these 

 nuclei and the further central connections of the cochlea with the superior olive, the 

 nuclei of the eye-moving nerves, the inferior quadrigeminate bodies, the medial geni- 

 culate bodies, and with the cerebellum and temporal lobes of the cerebral hemispheres 

 is given on pages 806, 807. 



THE NINTH NERVE THE GLOSSO-PHARYNGEAL 



The glosso-pharyngeal nerves are mixed nerves and each is attached to the medulla 

 by several roots which enter the postero-lateral sulcus, a short distance behind 

 the olivary body and in direct line with the facial nerve. 



The filaments, when traced outwards, are seen to blend, in front of the 

 flocculus, into a trunk which lies in front of the tenth nerve, but which passes through 

 a separate opening into the arachnoid and the dura mater and through the jugular 

 foramen. In the foramen this trunk lies in front and outside of the tenth nerve in 

 a groove on the petrous portion of the temporal bone, and in this situation two 

 ganglia are interposed in it, a superior or jugular, and an inferior or petrous. After 

 it emerges from the jugular foramen the glosso-pharyngeal nerve descends at first 

 between the internal carotid artery and the internal jugular vein and to the outer side 

 of the vagus; then, bending forwards and inwards, it descends internal to the sty- 

 loid process and the muscles arising from it , and t urning around the lower border of the 

 stylo-pharyngeus it passes between the internal and the external carotid arteries, 

 crosses the superficial surface of the stylo-pharyngeus, and runs forwards and up- 

 wards, internal to the hyoglossus muscle and across the middle constrictor and the 

 stylo-hyoid ligament, to the base of the tongue (fig. 707). 



Ganglia. The superior or jugular ganglion or ganglion of Ehrenritter, is a 

 small, ovoid, reddish-grey body which lies on the back part of the nerve-trunk in the 



