882 



THE NERVE SYSTEM 



The Vagus and Glossopharyngeal Nuclei are usually considered in their aggregate, 

 justified not only by their similarity in origin and central connections, but also 

 by the uncertainty which prevails regarding their peripheral interlacement and 

 complex terminations. Both nerves are in greater part afferent, but also contain 

 efferent axones. 



1. Afferent Portions. The afferent axones of the vagus arise from the cells in the 

 jugular ganglion and ganglion nodosum (ganglion of the trunk); the afferent axones 

 of the glossopharyngeal arise from the cells in its ganglion superius and ganglion 

 petrosum. The root fascicles of both nerves enter the medulla oblongata along 

 its dorsolateral groove, and the axones then undergo bifurcation into ascending 

 and descending rami, similar to those of the dorsal roots of the spinal nerves. 



FIG. 648. Primary terminal nuclei of the afferent (sensor) cranial nerves schematically represented in a sup- 

 posedly transparent brain stem, lateral view. The optic and olfactory centres are omitted. 



The ascending rami end in the nucleus alae cinereae (nucleus vagi et glossopkaryn- 

 gei); the descending rami collect to form a compact bundle called the tractus 

 solitarius or trineural fasciculus, 1 and terminating in a gray eel! column called the 

 nucleus of the solitary tract 2 a caudal prolongation of the nucleus alae cinereae. 

 Both tract and nucleus become attenuated caudad, to disappear in the fourth 

 cervical segment (relation with phrenic nerve nucleus), while cephalad it has 

 been traced as far as the region of the *ocus caeruleus (relation with trigeminal 

 nerve nuclei). 

 "From the cells of the nucleus alae cinereae and nucleus tractus solitarii axones 



'There are other "solitary" fasciculi in the nerve system, and the name "trineural fasciculus'' aptly 

 characterizes a tract which has for its object the mutual interchange of functions among the central nuclei of 

 the accessory, vagus, and glossopharynweal nerves. 



2 The nucleus of the solitary tract lies to the mesal side of the tract. Another nucleus has been described 

 by Mellus, lying lateral of the tract. 



