NERVES OF THE ENCEPHALON. 379 



roots, of which the internal is three or four times as large as 

 the other. 



These roots, before they penetrate the dura mater, most com- 

 monly unite into a single trunk, which goes almost directly for- 

 wards, and is enveloped in a neurileme. Passing through -fhe 

 cavernous sinus, it gets into the orbit by the sphenoidal fora- 

 men, and is spent upon the abductor oculi muscle. 



The Seventh Pair of Nerves is composed of the Facial and 

 the Auditory. 



The Facial Nerve (Nervus Facialis, Portio Dura Septimi, 

 Par Septimum) is placed in front of and above the auditory 

 nerve. It arises by two branches, which are perfectly distinct 

 from each other, and differ much in their size. The larger 

 one, which is placed within and above the other, arises from 

 the medulla oblongata at the most superior part of the corpus 

 restiforme, where the latter joins the tuber annulare. The 

 origin of the nerve is sometimes overlapped by the latter, so 

 that some few of its fibres appear to corne from the annular 

 protuberance, while they only pass through it, in their course 

 from the medulla oblongata. The second branch, which is 

 much smaller than the other, arises, by three or four filaments, 

 from that portion of the medulla oblongata which is placed be- 

 tween the first branch and the auditory nerve. 



The two branches of the facial nerve are kept distinct for 

 the distance of several lines before they unite. Proceeding 

 outwards and backwards, they reach the meatus auditorius in- 

 ternus, and then proceed, as a single cylindrical trunk, through 

 the aqueduct of Fallopius, to emerge at the stylo-mastoid fora- 

 men, for the purpose of being distributed upon the muscles and 

 skin of the head. ' 



The Auditory Nerve (Nervus Audilorius, Jlcusticus, Portio 

 Mollis Septimi) arises, in part, from the medullary stria3 on the 

 surface of the calamus scriptorius, and partly from the corpus 

 restiforme, between the glosso-pharyngeal nerve and the tuber 

 annulare. At its origin it is so extremely soft as not to bear 

 handling, and is too pulpy to present the appearance of fibres; 

 but, becoming more distant from the medulla oblongata, it is 

 harder and more fibrous. 



