CONNECTIONS AND FUNCTIONS OF CRANIAL NERVES 467 



ventrally and internally to the vestibular nucleus, both nuclei being in 

 close relation to the roof nuclei of the cerebellum. Many fibres of the 

 vestibular nerve pass apparently through these various nuclei on the 

 inner side of the restiform body into the cerebellum, where they make 

 connection with the roof nucleus or nucleus fastigii. By the nuclei of 

 Deiters and Bechterew the vestibular nerve is connected through the 

 dorsal longitudinal bundle and the descending vestibulo-spinal tract 

 with the motor nuclei of the cranial and spinal nerves. 



The use of the vestibular nerve is entirely connected with the 

 function of equilibrium. It is probably not concerned in conveying 

 auditory impressions, all its nerve fibres being derived ultimately 

 from the nerve- endings in the saccule and utricle and semicircular 

 canals. 



The seventh cranial nerve or facial nerve emerges from the brain 

 at the inferior margin of the pons, lateral to the point of exit of the 

 sixth nerve. It is almost entirely a motor nerve, but carries also 

 some sensory fibres for taste and general sensibility which it receives 

 from the nervus intermedius of Wrisberg. The motor nucleus of 

 the seventh nerve lies in the reticular formation, dorsally to the 

 superior olive, at some depth below the floor of the fourth ventricle. 

 From this nucleus the fibres first pass inwards and dorsally towards 

 the floor of the ventricle, where they collect to form a bundle which runs 

 upwards in the grey matter for a short distance and then turns sharply 

 in a ventro- lateral direction to emerge on the lateral aspect of the pons. 

 The fibres from the motor nucleus supply the muscles of the face, the 

 scalp, and the ear. Secretory fibres also run in the chorda tympani, 

 which is a branch of the facial. These, however, are probably derived, 

 like the sensory fibres, from the nerve of Wrisberg. The sensory 

 fibres of the nerve of Wrisberg originate in the nerve- cells of the genicu- 

 late ganglion, and, passing inwards with the main root of the facial, 

 divide into ascending and descending branches and end in the upper 

 part of the column of grey matter which receives also the sensory fibres 

 of the ninth and tenth cranial nerves. 



The ninth and tenth cranial nerves arise by a series of bundles of 

 nerve fibres from the side of the medulla. Both the ninth and tenth 

 are mixed visceral sensory and motor nerves. The sensory nucleus 

 is a column of grey matter lying laterally to the hypoglossal nucleus 

 just below the prominence on the floor of the fourth ventricle known 

 as the ala cinerea. The descending fibres of these nerves form a 

 well-marked bundle of white fibres known as the fasciculus solitarius, 

 or sometimes, from its supposed connection with the regulation of 

 respiration, the ' respiratory bundle of Gierke.' It may be traced down 

 as far as the uppermost part of the cervical cord, its fibres losing them- 

 selves on their way down among the cells of the enclosing grey matter. 



