THE CRANIAL NERVES. 481 



Connection with Deglutition. In the fauces and pharynx, the 

 glossopharyngeal nerve is sensitive to certain impressions, which 

 excite the muscles of the neighboring parts and bring into play the 

 mechanism of deglutition. The beginning of this process consists in 

 drawing backward and upward the base of the tongue, by which the 

 masticated food is carried through the isthmus of the fauces into the 

 pharynx. Next, the muscles of the pillars of the fauces (palatoglossal 

 and palatopharyngeal) close the opening of the isthmus, while the soft 

 palate is extended across the upper end of the pharynx, shutting off its 

 communication with the posterior nares ; and the constrictor muscles 

 of the pharynx then force its contents downward into the esophagus. 

 This is an involuntary reflex action. The contraction of the muscles, 

 and their coordination in a series of successive movements, will take 

 place even in a state of unconsciousness under the stimulus of food or 

 liquids in contact with the fauces and pharynx. This contact produces 

 an impression which is conveyed by the glossopharyngeal nerve inward 

 to the medulla oblongata, whence it is reflected in the form of a motor 

 impulse. 



Motor Properties of the Glossopharyngeal. Although this nerve 

 appears to be exclusively sensitive at its origin, it is found, when 

 examined outside the cranium, to possess motor properties. In the 

 experiments of Mayo on the ass, confirmed by those of Longet on 

 the horse and dog, irritation of the glossopharyngeal nerve in the 

 neck produced contraction of the stylopharyngeal muscle and the 

 upper part of the pharynx. These movements were the result of 

 direct motor action, since, in the experiments of Longet, they were 

 excited by irritating the peripheral extremity of the divided nerve. 



The glossopharyngeal, therefore, after its exit from the jugular fora- 

 men, is a mixed nerve. In addition to its original sensitive filaments, 

 it has received a branch of communication from the facial, and also 

 a branch from the pneumogastric. The latter branch is regarded, on 

 anatomical grounds, as made up, wholly or in part, of motor fibres 

 coming from the spinal accessory, through its anastomosis with the 

 pneumogastric. The results obtained by experiment also indicate a 

 double source for the motor fibres of the glossopharyngeal nerve. If 

 these were derived exclusively from either the facial or the spinal 

 accessory, the division of one or the other of these nerves above its 

 communicating branch would abolish completely the motor power of 

 the glossopharyngeal. But the experiments of Bernard and Longet, 

 in which the facial nerve was divided in the aqueduct of Fallopius, and 

 those in which the spinal accessory was destroyed on both sides, show 

 that the process of deglutition, though retarded, is not abolished by 

 either operation. 



Beside these anastomotic branches near its origin, the glosso- 

 pharyngeal is joined by a second branch from the facial, which accom- 

 panies it to the styloglossal muscle, and perhaps also to the pillars of 

 the fauces ; and, according to Cruveilhier, a branch derived from the 



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