620 FUNCTIONS OP THE CEREBRO -SPINAL NERVOUS SYSTEM. 



the posterior belly of the digastric muscles. It does not supply the muscles 

 of mastication. Its chorda tympani branch joins the lingual of the fifth, 

 and has been shown by Bernard to be the nerve by which the submaxillary 

 gland is excited to active secretion, while another branch is distributed to 

 the parotid ( 101). Experimental as well as anatomical researches leave 

 110 doubt that the Portio Dura is the general motor nerve of the face; min- 

 istering to the influence of Volition and of Emotion, and also being the 

 channel of the reflex movements concerned in respiration, as of other auto- 

 matic actions of the muscles. 



493. Although the functions of the Glosso-Pharyngeal nerve have been 

 heretofore alluded to in part, several questions still remain to be discussed 

 in regard to them. Reasons have been given for the belief, that it is chiefly 

 an afferent nerve, scarcely having any direct power of exciting muscular 

 contraction, but conveying impressions to the Medulla Oblongata, which 

 produce reflex movements of the motor nerves concerned in deglutition ( 89). 1 

 This view of this function was deduced by Dr. J. Reid from minute ana- 

 tomical investigation, and from a large number of experiments. Some ex- 

 perimenters assert that they have succeeded in exciting direct muscular 

 actions through its trunk; but these actions seem to be limited to the stylo- 

 pharyngei, palato-glossi, and superior constrictor muscles. 2 Much contro- 

 versy has taken place on the question, whether this nerve is to be regarded 

 as ministering, partly or exclusively, to the sense of Taste ; and many high 

 authorities have ranged themselves on each side. The question involves 

 that of the function of the Lingual branch of the 5th pair; and it is partly 

 to be decided by the anatomical relations of the two nerves respectively. 

 The Glosso-pharyngeal is principally distributed on the mucous surface of 

 the fauces, and on the back of the tongue; but, according to Valentin, it sends 

 a branch forwards, on either side, somewhat beneath the lateral margin, 

 which supplies the edges and inferior surface of the tip of the tongue, and 

 inosculates with the Lingual branch of the 5th. On the other hand, the 

 upper surface of the front of the tongue is supplied by this Lingual branch. 

 The experiments of Dr. Alcock, whose conclusions are borne out by Dr. J. 

 Reid, decidedly support the conclusion, that the gustative sensibility of this 

 part of the tongue is chiefly due to the latter nerve, being evidently impaired 

 by division of it. On the other hand, it is equally certain that the sense of 

 taste is not destroyed by section of the Lingual nerve on each side ; and it 

 seems also well ascertained, that it is impaired by section of the Glosso- 

 pharyngeal nerve. The pathological evidence bearing upon this point ap- 

 pears somewhat contradictory. Numerous cases have been recorded,' 1 in^ 

 which both common and gustative sensation were destroyed in the parts of 

 the tongue supplied by the 5th pair, when that nerve was paralyzed; in 

 some of these, the loss of the sense of taste appeared to extend itself to the 

 base of the tongue, but then there was evidence that the Glosso-pharyngeal 

 was involved in the paralysis. On the other hand, cases of paralysis of the 

 :~>th pair are related by Mr. Noble and by Vogt, 4 in which commom sensa- 

 tion was lost, whilst the sense of taste remained in the same parts; and Mr. 

 Noble relates another case, 5 in which there was loss of taste without impair- 

 ment of common sensation. The cases of Mr. Noble and Vogt would seem 



1 See also Vulpian, Rev. des Cours Seient., t. iii, p. 7">4. 



See CliMiiveaii, Journal de Physiologic; Brown-Squard, 18012, t. v, p. 1200. 



3 See ei-pr.-ially the cases recorded by Humbert;, in Miiller's Archiv, 1S:!S, II oft 

 iii; Todd and !'>wnian, in Physiological Anatomy, vol. i, p. 445; and Dixon, in 

 Med -Chir. Trans., vol. xxviii. 



4 Medical Gazette, Oct. :2oth, 1834; and Miiller's Archiv, 1840, p. 72. 

 6 Medical Gazette, Nov. *2lst, 1835. 



