THE CRANIAL OR ENCEPHALIC 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 

 oblorigata 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 striae (linece transversce, strice medullares*), as is admitted in the 

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

 discover these striae 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 Schroeder 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. 1 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 petrosum or ganglion of Andersch, in 

 which it is somewhat difficult to distinguish the motor filaments of the 

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

 medulla oblongata (Fig. 338, 2). 



Course and Termination. Scarcely has the glosso-pharyngeal nerve 

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

 concavity looks forward, behind the large branch of the os hyoides, included 

 at first between a fold of the guttural pouch, then between the latter and 



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

 remove all the doubts existing in the minds of a large number of anatomists, as to the 

 nature of the glosso-pharyngeal nerve. It evidently possesses at its origin, as motor 

 filaments, those arising from the same part as the facial nerve, and as sensitive filaments 

 those from the corpus restiforme. Besides, we may object to the opinion which would 

 also attribute the motor property of the glosso-pharyngeal nerve to the anastomosing 

 bianche-< passing between it and the seventh pair, on the ground that thf se anastomoses 

 are far from being constant, und that in i-ome species they are always totally absent. 



