THE NERVOUS SYSTEAf 



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auditory meatus, but escaping from the internal ear by the 

 aqueduct of Fallopius, it leaves the eighth nerve, and passing 

 beneath the parotid gland, finds its way on to the face, about 

 1 J inches below the articulation, over the external masseter 

 muscle. During this short course the nerve has supplied the 

 small superficial petrosal nerve, a nerve to the stapedius muscle 

 of the middle ear, and the chorda tympani. The latter takes a 

 remarkable course through the petrous temporal bone, supplies 

 fibres to the submaxillary and sublingual glands, and eventually 

 joins the lingual nerve of the glands, there assisting the special 

 nerve of taste. Besides the above 

 branches, the main trunk of the 

 facial, on its way to the face, 

 has supplied motor fibres to the 

 muscles of the external ear, and 

 sensory fibres to the skin of that 

 part ; motor fibres to the digastric 

 muscle, to the orbicularis of the 

 eye, and the corrugator of the 

 brow. The main trunk on the 

 surface of the masseter muscle 

 divides into two branches, which 

 between them supply all the 

 muscles of the face, lips, cheek, 

 and nostril with motor power. 

 The seventh nerve is the nerve 

 of expression. In this connection 

 it supplies the external ear and 

 all the muscles of the face and 

 lips. Paralysis of this nerve pro- 

 duces a typical facial expression 

 (Fig. 155). The ear droops, the FlG - 155.— Characteristic Facial 

 eye remains open the upper lip Hl^ZZlll^l^Z 

 is drawn towards the sound side, 



is elongated and flabby ; the lower lip droops, and saliva runs 

 from the mouth ; the nostrils are elongated, and the face 

 possesses a stupid, vacant look. Nutritive change may occur 

 to the eye in consequence of exposure, and deafness is present 

 owing to paralysis of the muscle of the middle ear. Bernard 

 pointed out that if both facial nerves be divided in the horse, 

 and the animal galloped, suffocation results in consequence of 

 the nostrils being unable to dilate, and the horse unable to 

 breathe through the mouth. The sensory fibres which join the 

 seventh do so through the nerve of Wrisberg ; this supplies 

 the mucous membrane of the anterior two-thirds of the 

 tongue. Through the chorda tympani, secretory fibres are 



