628 STRUCTURE OF THE BULB, PONS, & MID-BRAIN. [OH. XLiv. 



ear. The ventral root originates from a collection of nerve-cells 

 external to the glosso-pharyngeal nucleus, called the inner or 

 dorsal auditory nucleus. This root becomes the vestibular division 

 of the auditory nerve and is distributed to the vestibule and 

 ampullae of the semicircular canals of the internal ear. The 

 vestibular (Scarpa's) ganglion on the vestibular portion and the 

 spiral ganglion on the cochlear division have bipolar cells and 

 represent a spinal ganglion (see Ear). 



rt ^Ventral to the inner auditory nucleus is a collection of large 

 nerve-cells, formerly called the outer auditory nucleus, but now 

 known as the nucleus of Deiters. Its cells are connected with those 

 of the cerebellum. 



9, 10, ii. These three nerves are called respectively the 

 glosso-pharyngeal, vagus or f >neum 9 as ^ r ^ an d spinal accessory, 

 They arise from an area of grey matter, reaching from about the 

 middle of the floor of the fourth ventricle down into the spinal 

 cord, as low as the origin of the sixth or seventh cervical nerves. 

 The nuclei of the three nerves are closely connected with each 

 other. 



In addition to this combined nucleus, which is composed of 

 small cells, there are certain lateral contributions, namely : 

 i. the nucleus ambiguus, a large celled nucleus, which lies on 

 the lateral side of the reticular formation and is an accessory 

 origin of the vagus and glosso-pharyngeal ; ii. the fasciculus soli- 

 tarius, which is situated in the bulb, ventral and a little lateral 

 to the combined nucleus, and which is also called the ascending 

 root of the glosso-pharyngeal nerve or the respiratory bundle ; 

 and iii. the spinal portion which takes origin from a group of 

 cells lying in the extreme lateral margin of the anterior cornu. 

 This is the origin of the spinal accessory ; it corresponds to 

 the antero-lateral nucleus of the bulb, and the lateral part of 

 the grey matter of the spinal cord. The fibres of the spinal 

 origin of the nerve pass from these cells through the lateral 

 column to the surface of the cord. 



The fibres from the combined nucleus, chiefly from the median 

 part, pass in a ventral and lateral direction through the reticular 

 formation, then ventral to or through the gelatinous substance and 

 the strand of fibres connected with the fifth nerve, to the surface 

 of the bulb. 



The bundles of fibres of the fasciculus solitarius start in the 

 lateral grey matter of the cervical cord and higher in the reticular 

 formation of the bulb ; they run longitudinally forwards to pass 

 into the roots of the ninth nerve. 



The glosso-pharyngeal and vagus portions of the combined 



