CHAP. XIX.] THE FACIAL NERVE. 105 



carotid artery, it forms a very celebrated anastomosis with the 

 sympathetic, by means of two large and distinct branches, and it 

 sometimes anastomoses with the nasal branch of the fifth. 



Anatomy points to the function of this nerve as distinctly as it 

 does to that of the fourth. The sixth nerve can have no other 

 office than that of regulating the movements of the abductor muscle 

 of the eye. Experiment fully confirms this conclusion, and a few 

 cases have been observed in which internal strabismus was found 

 to accompany compression of the nerve by a tumor. 



Of the Facial Nerve. (Portio dura of the seventh pair.) This 

 is one of the most interesting and remarkable of the motor nerves. 

 Its close proximity to the auditory nerve led Willis to class it along 

 with that nerve. The former nerve is soft in its structure, and 

 its bundles loosely coherent; the latter is more compact, and sur- 

 rounded by a neurilemma of sufficient density to give to it a power 

 of resistance very superior to that of its neighbour. 



These two nerves lie in a fossa situate on either side of the 

 medulla oblongata, and behind the posterior edge of the pons, 

 bounded on the outside by a small lobule of the cerebellum, called 

 the flock by Reil, or the lobule of the vagus or of the auditory nerve; 

 the floor of this fossa is formed by the restiform column. The 

 portio dura nerve, which lies inside the portio mollis, penetrates 

 the restiform column, and through it may be traced to the central 

 part of the medulla oblongata, the olivary columns, where it con- 

 nects itself with the vesicular matter. 



In examining the distribution of the facial nerve, it will be found 

 convenient to divide it into three stages, and to enumerate its 

 branches in each stage. 



The first stage is intracranial, from its origin to its exit at the 

 internal auditory meatus. In this stage it forms a connexion with 

 the auditory nerve by the portio intermedia of Wrisberg, an oblique 

 branch of communication, which seems like a fasciculus of fibres 

 passing off from the portio dura, and accompanying the auditory 

 nerve into the labyrinth. This branch was described by Arnold 

 and Gcedechens as a second root of the facial nerve, but inasmuch 

 as it does not form a connexion with the centre, distinct from that 

 which the principal fibres of the nerve have with it, this view is not 

 tenable. Regarding the facial as a motor nerve, this branch may 

 possibly be viewed, as conveying motor influence to the muscular 

 apparatus of the cochlea, which we have discovered. 



The second stage is contained in the aqueductus Fallopii. In 

 its passage through this canal a gangliform swelling is formed on 



