008 HANDBOOK OF PHYSIOLOGY. 



IXtli Nerve. Distribution. The glosso-pharyngeal nerve gives fila- 

 ments through its tympanic branch (Jacobson's nerve), to the fenestra 

 ovalis and fenestra rotunda, and the Eustachian tube, parts of the mid- 

 dle ear; also, to the carotid plexus, and through the petrosal nerve, to 

 the spheno-palatine ganglion. After communicating, either within or 

 without the cranium, with the vagus, and soon after it leaves the cra- 

 nium, with the sympathetic, digastric branch of the facial, and the 

 accessory nerve, the glosso-pharyngeal nerve parts into the two principal 

 divisions indicated by its name, and supplies 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 caecum in the 

 middle line, and to near the tip at the sides and inferior part. 



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

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



1. Motor fibres are distributed to the palato-pharyngeus, the stylo- 

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



2. Sensory fibres in- the parts which it supplies, and a centripetal 

 nerve through which impressions are conveyed to be reflected to the ad- 

 jacent muscles. 



o. Fibres for the SPECIAL XERVE of taste (from its fibres derived from 

 the fifth, Gowers), in till the parts of the tongue and palate to which it is 

 distributed. After many discussions, the question, Which is the nerve 

 of taste? the chorda tympani, the gustatory, or the glosso-pharyngeal? 

 may be most probably answered by stating that they are not them- 

 selves, strictly speaking, nerves of this special function, but through 

 their connection with the fifth nerve. For very numerous experiments 

 and cases have shown that when the trunk of the fifth nerve is paralyzed 

 or divided, the sense of taste is completely lost in the superior surface 

 of the anterior and lateral parts of the tongue, at the back of the tongue, 

 and on the soft palate and palatine arches. The loss is instantaneous 

 after division of the nerve, and, therefore, cannot be ascribed wholly to 

 the defective nutrition of the part, though to this, perhaps, may be 

 ascribed the more complete and general loss of the sense of taste when 

 the whole of the fifth nerve has been paralyzed. 



The Xth Nerve ( Vagus or Pneumogastric) . 



The origin of the Vagus nerve is, as we have just seen, situated in 

 the lower half of the calamus scriptorins in the ala cinerea (fig. 365). 

 Its nucleus is said to represent the cells of Clarke's (posterior vesicular) 

 column of the spinal cord. In origin it is closely connected with the 

 ninth, eleventh, and the twelfth. The combined glosso-pharyngeal- 



