THE CJRANIAL OR ENGEPEALIC NERVES. 727 



or its properties, because, notwithstanding these anastomoses, its proper 

 fibres preserve their complete independence. 



8. Eighth Pair, or Auditory Nerves. (Figs. 324, 338.) 



This, is the nerve of hearing, and affects a very simple disposition, which 

 we will sum up in a few words. 



Origin. — The auditory nerve (portio mollis) proceeds from the medulla 

 oblongata by two roots, an anterior or lateral, and a posterior. The latter 

 (Fig. 323, 20) commences on the floor of the fourth ventricle by some 

 convergent strise (linea transversm, strice medullares), as is admitted in Ahe 

 majority of treatises on human anatomy, though we have never been able to 

 discover these striaa in the domesticated animals ; it is afterwards directed 

 outwards in winding round the posterior cerebellar peduncle, and unites with 

 the anterior root on the side of the medulla oblongata. The latter root 

 (Fig. 338, g), consists of a single fasciculus joined with that of the facial, 

 and escapes from between the fibres of the corpus restiforme. The nucleus 

 of the auditory nerve has been discovered by Schrceder Van der Kolk, a 

 little below that of the facial nerve. 



Course and Termination. — These two roots immediately unite into a 

 ■ single soft cord situated behind that of the seventh pair, with which it is 

 directed outwards to reach the internal auditory hiatus (or meatus.) There 

 it divides into two branches — an anterior and posterior, whose fasciculi 

 traverse the foramina at the bottom of that hiatus : the former to gain the 

 axis of the cochlea (the cochlear branch), and the latter the semicircular 

 canals (vestibular branch.) The description of these two branches will be 

 deferred till we come to the sense of hearing. 



9. Ninth Pair, or Glosso-Pharyngeal Nerves. (Figs. 338, 3 ; 342, 10.) 

 The glosso-pharyngeal is a mixed nerve, which carries general sensation, 

 with gustative sensibility, into the posterior third of the tongue, and excites 

 ( ontraction of the pharyngeal muscles. , „ , , 



Origin —This nerve originates on the side of the medulla oblongata, 

 behind the eighth pair, by eight or ten fine roots, some of which are 

 implanted in the corpus restiforme, while the others, the smallest number, 

 escape, like the filaments of the facial nerve, from the interstice between 

 that body and the lateral column of the medulla oblongata.^ These roots 

 soon unite in a single cord, which issues from the cranium by a particular 

 orifice in the posterior foramen lacerum, and at this point exhibits a grey 

 oval-shaped enlargement- the ganglion pelrosum ov ganghonof Andersji m 

 which it is somewhat difiicult to distinguish the motor filaments of ho 

 nerve from those which arise between the lateral and superior columns of the 



"^'SLflTT^^^^^^^^ lias the glosso-pharyngeal nerve 



escaped from the cranium, before it descends, in describing a curve whose 

 concavity lo^ks forward, behind the large branch of the os hyoides, included 

 atfirTbetweenafoldo'f the guttural pouch, then between the latter and 

 1 This disposition wliich is readily exposed in the Horse, appears to us sufficient to 

 1 his disposition, «''i the minds of a large number of anatomists, as to the 



remove all the doubts existing nth^^^^^ ^^ .^^ ^ ^^ ^^^^^ 



fif^rntf thosetstSfro^mfhe same part as the faJa^nerve, and as sensidvefllaments 

 filaments, tnose arisiu„ """ ■RpSdet we mav obicct to t le opinion which would 



those from the c<n-P"%'^^*^^°™^; „?7,p '',o„3^ nerve to the anastomosing 



also -ttrihute.the motor Ijroperty of thejtes ^^^^ ^^^^^ anas.omosJ 



a'rtS frrSg^o^Xnt! :nd thaVr.ome Voies they'are always totally ab=cn:. 



