THE FACIAL NERVE. 



337 



of gustatory; 17, inferior dental; 18, mylo-hyoid nerve; 19, incisive 

 branch of dental nerve; 20, branch of mental, cut; <z, pterygoideus in- 

 ternus ; b, part of pterygoideus externus muscle ; c, mylo-hyoid muscle ; 

 d, portion of anterior belly of the digastric ; e, hypoglossal muscle ; J\ 

 portion of submaxillary gland. 



OF THE SEVENTH PAIR, THE FACIAL NERVE. 



This nerve arises from the upper part of the groove between the oli- 

 vary and restiform bodies, and near the pons. varolii. With The seventh 

 the auditory nerve, or portio mollis, it constitutes the seventh P air > or facial, 

 nerve in the nomenclature of Willis, and derives the name portio dura, 

 under which it sometimes passes, from the density and closeness of its 

 texture. It supplies all the muscles of the face except those of mastica- 

 tion, which are supplied by the fifth nerve, those of the palate, the sta- 

 pedius, laxator tympani, and tensor tympani ; also the muscles of the ex- 

 ternal ear, and some of those of the tongue. The facial is a centrifugal 

 nerve. If irritated near its origin, there is no sensation of pain ; but sub- 

 sequently it obtains fibres from other sources, as from the fifth and the 

 pneumogastric. After it has been joined by these, irritation is acutely 

 felt. It is therefore to be regarded as the general motor nerve of the 

 face, influencing the function of respiration through reflex action, but not 

 being connected with the function of mastication. Injury of it produces 

 paralysis of the parts to which it is distributed, as, for example, the orbic- 

 ularis palpebrarum, causing inflammation of the eye and opacity of the 

 cornea, through inability of that organ to free itself from dust and spread 

 the lachrymal secretion over its surface. In like manner, the sense of 

 hearing may be injured through loss of control over the muscular struc- 

 tures of the ear, and the acuteness of the sense of smell diminished from 

 Fig.iw. inability to introduce the air in a 



strong current, or the sense of taste, 

 if the point of injury be previous to 

 the giving off of the chorda tympani. 

 In paralysis of the facial nerve the 

 muscles of the face become powerless, 

 and the countenance, therefore, dis- 

 torted. 



ILLUSTRATION OF THE FACIAL NERVE. 



Fig. 167 : 1, trunk of the facial 

 at its emergence from the aqueduct 

 of Fallopius ; 2, occipito- auricular 

 branch ; 3, auricular of the cervical 

 plexus ; 4, twig of the occipital mus- 



The facial nerve. 



