THE CENTRAL NERVOUS SYSTEM 



821 



sensation on the face, conjunctiva, the mucous membranes of the 

 mouth and nose, and the structures contained in them, and, accord- 

 ing to Gowers, special sensation, through branches given off to the 

 facial and glosso-pharyngeal nerves, on the organs of taste.* Com- 

 plete paralysis of the nerve causes loss of movement in the muscles 

 of mastication, sometimes impaired hearing, and loss of common 

 sensation in the area supplied by it. Loss 

 or impairment of taste in the correspond- 

 ing half of the tongue is also often seen 

 disease involving the sensory root, 



Nu. 



n. V. 



in 



although not in affections of the trunk 

 of the nerve, since the taste fibres leave 

 it near its origin (Gowers) . Both taste and *'' 

 touch are lost in the monkey in the an- 



A". 



A'u.m.jjr.ji. T 7 . 



FIG. 343. SCHEME OF MOTOR AND SENSORY NEURONS OF TRIGEMINUS 

 (GEHUCHTEN). 



G. s. G., Gasserian ganglion ; Nu. m. m. n. V., nucleus of the descending root ; 

 Nu. m. pr. n. V., chief motor nucleus of the fifth nerve ; Rad. desc. mes. n. V., 

 accessory motor nucleus, sometimes called the descending root ; Tr. sp. n. V., 

 tractus spinalis, or spinal root of the fifth. 



terior two-thirds of the tongue after intracranial section of the 

 trigeminus (Sherrington). 



Vaso-motor changes are occasionally, and ' trophic ' changes 

 frequently, observed in disease of the fifth nerve. The trophic 



* It should be stated that some physiologists believe that the glosso- 

 pharyngeal is the nerve of taste, and that none of the taste fibres go to 

 the sensory nuclei of the fifth nerve. The majority hold that the glosso- 

 pharyngeal supplies the posterior third, and the chorda tympani and 

 lingual the anterior two-thirds of the tongue with gustatory fibres. The 

 removal of the Gasserian ganglion and the adjacent portion of the fifth 

 nerve for severe and persistent neuralgia, has afforded opportunities to 

 test this question. But, unfortunately, the results described by various 

 observers do not agree, some finding that taste is unimpaired, others that it 

 is abolished. Gowers states that the gustatory sensations may persist for 

 some time after the operation, although ultimately (in two or three weeks) 

 they disappear. It may be, however, that this disappearance is due to secon- 

 dary changes produced in the end-organs of the true taste fibres, the taste 

 buds, by degeneration of the supporting cells consequent on section of the 



