548 THE CRANIAL NERVES. 



external rectus muscle, it is beneath the other nerves, but above the 

 ophthalmic vein. While passing along the internal carotid artery in 

 the cavernous sinus, it is joined by several filaments of the sympathetic 

 from the carotid plexus. According to Bock it is joined in the orbit 

 by a filament from Meckel's ganglion. — (" Beschreibung des Fiiuften 

 Nervenpaares." 1817.) 



Varieties. — Absence upon one side has been recorded, its place being supplied 

 by a branch from the third nerve. (General!.) 



SEVENTH PAIR OF NESVES. 

 In the seventh cranial nerve of AVillis are comprised two nerves 

 having a distinct origin, distribution, and function. One of these, the 

 facial, is the motor nerve of the face ; the other, the auditory, is the 

 special nerve of the organ of hearing. Both enter the internal auditory 

 meatus in the temporal bone, but they are soon separated from each 

 other. The facial nerve being the firmer of the two, was termed the 

 portio dura, the other being called the portio mollis. 



r AC I All NERVE. 



Surface attachment. — The facial nerves appear, on each side, at 

 the inferior margin of the pons, and in a Ime with the roots of the fifth 

 pair. Each nerve emerges from the medulla oblongata, in the outer 

 part of the depression between the olivary body and the diverging resti- 

 form body (inferior peduncle of cerebellum), and is often firmly ad- 

 herent, as a flattened band, to the lower edge and even for a short 

 distance to the upper surface of the pons. On its outer side is the 

 auditory nerve. A separate fasciculus of the facial nerve {intermediale 

 2Kirt) is sometimes attached to both auditory and facial nerves. 



Deep origin. — The fibres of the facial nerve course backwards, in- 

 wards, and a little upwards to reach the outer side of the column of 

 nerve-cells, which lies beneath the emmentia teres (common nucleus of 

 sixth and facial nerves). In it many of the fibres end. A few pass 

 inwards, and cross at the raphe to the opposite side of the medulla. 

 Other fibres ascend to the upper extremity of the nucleus, around which 

 they turn, and descend, as a compact bundle, on its inner side. These 

 fibres finally radiate forwards and outwards to the column of nerve- 

 cells, prolonged downwards from the motor nucleus of the fifth nerve, 

 and also to the superior olivary body. 



Course. — The facial nerve is inclined outwards with the auditory 

 nerve, from its place of origin, to the internal auditory meatus. The 

 facial lies in a groove on the auditory nerve, and the two are united in 

 the auditory meatus by one or two small filaments. At the bottom of 

 the meatus the facial nerve enters the aqueduct of Fallopius, and follows 

 the windings of that canal to the lower surface of the skull. The 

 nerve passes through the temporal bone at first almost horizontally 

 outwards, between the cochlea and vestibule ; on reaching the inner 

 wall of the tympanum it is turned suddenly backwards above the fenestra 

 ovalis towards the pyramid. At the place where it bends, the nerve 

 presents a reddish fiangliform cjilargemenf, sometimes called the (jenku- 

 latc gamjUon, which marks the place of junction of several nerves. 

 Opposite the pyramid it is arched downwards behind the tympanum 

 to the stylo-mastoid foramen, by which it leaves the osseous canal. It 

 is then continued forwards through the substance of the parotid gland. 



