660 THE NERVOUS SYSTEM 



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

 then ventral to or through the gelatinous substance and strand of fibers 

 connected with the fifth nerve, to the surface of the bulb. 



The fibers from the nucleus ambiguus join the combined nerve, chiefly 

 the vagus and the glosso-pharyngeal. 



The bundles of fibers of the fasciculus solitarius start in the lateral gray 

 matter of the cervical cord and higher in the reticular formation of the bulb, 

 run longitudinally forward, to pass into the roots of the ninth nerve. It is 

 composed of sensory fibers, chiefly of the glosso-pharyngeal, and of the 

 pars intermedia of the facial. 



The glosso-pharyngeal nerve gives filaments through its tympanic branch 

 (Jacobson's nerve), to the fenestra ovalis and fenestra rotunda, and the Eu- 

 stachian tube; also to the carotid plexus, and through the petrosal nerve, to 

 the spheno-palatine ganglion. After communicating with the vagus and, 

 soon after it leaves the cranium, with the sympathetic, with the digastric 

 branch of the facial, and the accessory nerve, the glosso-pharyngeal divides 

 into the two principal divisions indicated by its name. These divisions 

 supply the mucous membrane of the posterior and lateral walls of the 

 upper part of the pharynx, the Eustachian tube, the arches of the palate, 

 the tonsils and their mucous membrane, and the tongue as far forward 

 as the foramen cecum in the middle line, and to near the tip at the sides and 

 inferior part. 



Functions. The glosso-pharyngeal nerve contains some motor fibers, 

 together with fibers of common sensation and the sense of taste. 



Motor fibers are distributed to the palato-pharyngeus, the stylo-pharyn- 

 geus, palato-glossus, and constrictors of the pharynx. 



Sensory fibers of touch and of common sensation are distributed to the 

 pharynx, the tonsils, and posterior palate. Nerves of taste are supplied to 

 the taste buds on the posterior third of the tongue and to the fauces. 



The Tenth Nerve, Vagus or Pneumogastric Nerve. The origin of the 

 vagus nerve is, as we have just seen, situated in the lower half of the floor of 

 the fourth ventricle, figure 378. Its nucleus is said to represent the homo- 

 logue of the cells of Clarke's column of the spinal cord. In origin it is 

 closely connected with the ninth, eleventh, and the twelfth. The com- 

 bined glosso-pharyngeal- vago-accessory nuclei lie outside of, close to, and 

 parallel with the nucleus of the twelfth. There are two main vagal nuclei, 

 one motor, the other sensory. The motor nucleus gives rise to a large 

 group of efferent fibers of wide distribution in the body all belonging to the 

 bulbar autonomies of Langley. 



Distribution. It has, of all the nerves, the most varied distribution and 

 functions, either through its filaments, or through sensory fibers which 

 are mingled in its branches, and give rise to most varied reflex reactions. 

 The vagus supplies sensory branches, which accompany the sympathetic 



