826 



THE NERVOUS SYSTEM 



The glosso-palatine nerve (nervus inter medius, sensory root of facial, etc.) is a mixed nerve 

 but largely sensory. It accompanies the facial from a short distance beyond the geniculura (genu 

 externum) of the facial to its attachment to the brain stem. Its sensory fibres arise as T-fibres of 

 the cells of the geniculate ganglion (at the geniculum of the facial) . The peripheral processes go as 

 the chorda tympani to supply the epithelium of the anterior part of the tongue and that of the 

 palate, especially of the palatine arches. The central processes enter the brain stem, bifurcate 

 into caudal and cephaKc branches, and find their nucleus of termination in a superior extension 

 of the nucleus of the sohtary tract (the ventral portion of the nucleus of the ala cinerea). The 

 geniculate ganghon contains some cell-bodies of sympathetic neurones, left over in it during 

 the period of migration form its homologue of the ganglion crest. 



The efferent fibres of the glosso-palatine arise from cell-bodies lying dorso-medial to the 

 nucleus of the facial and in the level between this and the nucleus of the masticator nerve 

 superior to it. Its cells are usually scattered in the reticular formation in line with the dorsal 

 efferent nucleus of the vagus. Since most of its fibres, at least, are concerned with sympathetic 

 neurones (terminate in sympathetic ganglia) and convey secretory impulses destined for the 

 sahvary glands, it has been called the nucleus salivatorius. 



Fig. 652. — Transverse Section through Pons and Portion of Cerebellum at Level 

 OF Nuclei and Root Filaments of Abducens and Facial Nerves. (From Villiger.) 

 Kucleus globosus 



Kucleus embohformis 

 Brachium conjunctivum 



Restiform body 



Tractus nucleo-cere- 

 bellaris 



Medial longitu- 

 dinal fasciculus 



Root filaments 

 of facial 



Nucleus of facial 



Superior olive 



Tractus thalamo-olivaris 

 Corpus trapezoideum and medial 

 lemniscus 



Pjramid 



Fourth ventricle 

 Brachium conjunctivum 



Genu of facial nerve (pars 

 ■^ / ascendens n. facialis) 



Tractus nucleo-cerebellaris 



Nucleus of abducens 



Root filaments of 

 abducens 



Nuclei and root of 

 ~ trigeminus 



Corpus trape- 

 zoideum 



Brachium pontis 



Nucleus reticularis 

 tegmenti 

 Deep stratum of pons 



Superficial ^atr^itum uf pun:s 



Pyramid 

 Medial stratum of pons 



The abducens is a small, purely motor nerve, which supplies the lateral rectus muscle 

 of the eye. Its nucleus of origin lies close to the mid-line in the medial eminence of the floor 

 of the fourth ventricle, and in Une with that of the hypoglossus. Its root-fibres, uncrossed, pursue 

 a ventral course, inclining a little laterally and curving inferiorly to emerge from under the 

 inferior border of the pons. They pass lateral to the pyramid, and often between some of its 

 fasciculi. The nucleus receives cortical or voluntary impulses by way of the pyramidal 

 fasciculi chiefly of the opposite side. Its connection with the auditory apparatus and the 

 medial longitudinal fasciculus has already been noted. It probably receives afferent impulses 

 through the fibres of the trigeminus as well as by fibres descending from the nuclei of termi- 

 nation of the optic nerve. It is also associated, by way of the medial longitudinal fasciculus, 

 with the nucleus of the oculomotor nerve of the same and opposite sides. 



The trigeminus is considerably larger than any of the nerves inferior to it, and has the most 

 e.xten.sive central connections of any of the cranial nerves. It is a purely sensory nerve which 

 enters through the brachium pontis in line with the facial nerve. It serves as the nerve of 

 general sensibility for the face from the vertex of the scalp downward, and thus it corresponds 

 to the afferent fibres (dorsal root) for all the nerves giving motor supply to structures underlying 

 its domain. Its fibres arise from its large, trilobtul, semilunar ((jasscrian) ganglion, situated 

 outside the brain. This corresponds to the dorsal root ganglion of a spinal nerve, and its cells 

 give off the characteristic T-fibres with peripheral and central branches. The central or 

 afferent branches upon entering the brain-stem bifurcate into ascending and descending divi- 

 sions, just as the entering dorsal root-fibres of the spinal nerves, and find their nucleus of ter- 

 mination in a dorso-lateral cohnnn of grey substance, lying deeply and extending longitudinally 

 through the Ijrain stern, and consisting of the upward continuation of the gelatinous substance 

 of Rolando of tlio spinal cord. Opposite the entrance of the nerve is a considerably thickened 

 fiortion of fliis column of gnsy sulKstancc, known as the sensory nucleus of the trigeminus, and 

 the remainder below is called the nucleus of the s]>inal tract (fig. 047). Both parts are equally 

 "sensory." After bifurcation the branches of the entering fibres of the trigeminus terminate 

 about the cells of these nuclei. The descending branches are much longer than the ascending, 



