CRANIAL NERVES. 109 



Properties. Undoubtedly a motor nerve at its origin, but in its course 

 receives sensitive filaments from the 5th pair and the pneumogastric. 



Irritation of the nerve; after its emergence from the stylo-mastoid fora- 

 men, produces convulsive movements in all the superficial muscles of the 

 face. Division of the nerve at this point causes paralysis of these muscles 

 on the side of the section, constituting facial paralysis ; the phenomena o ( f 

 which are, a relaxed and immobile condition of the same side of the face ; 

 the eyelids remain open, from paralysis of the orbicularis palpebrarum ; 

 the act of winking is abolished ; the angle of the mouth droops, and saliva 

 constantly drains away; the face is drawn over to the sound side ; the face 

 becomes distorted upon talking or laughing ; mastication is interfered with, 

 the food accumulating between the gums and cheek, from paralysis of the 

 buccinator muscle; fluids escape from the mouth in drinking; articulation 

 is impaired, the labial sounds being imperfectly pronounced. 



Properties of the branches given off in the aqueduct of Fallopius. The 

 Large petrosal, when irritated, throws the levator palati and azygos uvulae 

 muscles into contraction. Paralysis of this nerve, from deep-seated lesions, 

 produces a deviation of the uvula to the sound side, a drooping of the palate, 

 and an inability to elevate it. 



The Small petrosal influences hearing by animating the tensor tympani 

 muscle ; when paralyzed, there occurs partial deafness and an increased 

 sensibility to sonorous impressions. 



The Tympanitic branch animates the stapSdius muscle, and influences 

 audition. 



The Chorda tympani influences the circulation and the secretion of 

 saliva, in the sub-maxillary glands, and governs the sense of taste in the 

 anterior two-thirds of the tongue. Galvanization of the chorda tympani 

 dilates the blood vessels, increases the quantity and rapidity of the stream 

 of blood, and increases the secretion of saliva. Division of the nerve is 

 followed by contraction of the vessels, an arrestation of the secretion, and 

 a diminution of the sense of taste, on the same side. 



Function. The facial is the nerve of expression, and coordinates the 

 muscles employed to delineate the various emotions, influences the sense 

 of taste, deglutition, movements of the uvula and soft palate, the tension of 

 the membrana tympani, and the secretions of the sub-maxillary and parotid 

 glands. Indirectly influences smell, hearing and vision. 



8th Pair. Portio Mollis. Auditory Nerve. 



Apparent Origin. From the upper and lateral portion of the medulla 

 oblongata, just below the margin of the pons Varolii. 



