554 THE CRANIAL NERVES. 



with branches of the pneumogastric to the mucous membrane and the 

 superior and middle constrictors of the pharynx. The muscles, accord- 

 ingly, to which this nerve is directly or indirectly distributed are those 

 by which the tongue is drawn backward (styloglossal), the larynx and 

 pharynx elevated (digastric and stylopharyngeal), and the upper part 

 of the pharynx contracted (superior and middle constrictors) ; that is, 

 those concerned in the act of deglutition. 



Physiological Properties of the Glossopharyngeal. The glossopha- 

 ryngeal nerve is evidently for the most part a nerve of sensibility. Its 

 origin from the tract of gray matter in the medulla oblongata correspond- 

 ing to the posterior horns of gray matter in the spinal cord, the distinct 

 ganglion located upon its trunk in the jugular foramen, and the fact that 

 it is mainly distributed to the mucous membranes of the tongue and 

 pharynx, all indicate its resemblance in anatomical arrangement to other 

 well known sensitive nerves or nerve roots. The result of direct experi- 

 ment corroborates this view. Longet, in irritating the glossopharyngeal 

 nerve within the cranium, was never able to produce muscular contrac- 

 tion ; and although Chauveau, in experimenting upon this nerve in the 

 same situation in recently killed animals, saw its galvanization followed 

 by contraction of the upper part of the pharynx, the effect may have 

 been due to reflex action, since the nerve w~as still in connection with 

 the medulla oblongata. This conclusion is rendered certain by the in- 

 vestigations of Reid, 1 who found that irritation of the glossopharyngeal 

 nerve produced movements of the throat and lower part of the face ; 

 but that these movements were, in a great measure, reflex and not 

 direct, since they were also produced after the nerve had been divided, 

 by applying the irritation to its cranial extremity. Its sensibility to 

 mechanical or galvanic irritation, however, appears to be of a low grade, 

 as compared with that of the trigeminal nerve. While some observers 

 (Reid) found its irritation in the living animal, outside the jugular fora- 

 men, give rise to evident signs of pain, others (Panizza) have failed to 

 see any indications of suffering from this cause ; and others still (Longet) 

 speak of the signs of pain, thus produced, in a more or less uncertain 

 manner. This variation in the observed results is sufficient to show the 

 inferior capacity of the glossopharyngeal nerve for the receipt of painful 

 impressions; since no experimenter has ever doubted the acute sensibility 

 of the fifth pair. 



But notwithstanding the comparative deficiency of the nerve itself, 

 and the parts to which it is distributed, in ordinary sensibility, it serves 

 to transmit sensitive impressions of a special character, which are con- 

 nected with two different but associated functions, namely : 1. The sense 

 of taste, and, 2. The reflex act of deglutition. 



Connection with the Sense of Taste. The power of perceiving sensa- 

 tions of taste exists not only in the anterior portion of the tongue which 



1 Todd's Cyclopaedia of Anatomy and Physiology. Article, Glossopharyngeal 

 Nerve. 



