286 THE NERVOUS SYSTEM 



sinus it receives fibers from the first division of the fifth and from 

 the sympathetic. 



Function. The function is indicated in its distribution. It 

 is insensible at its origin. Stimulation produces contraction of 

 the external rectus; section causes paralysis of that muscle and 

 consequent internal strabismus and diplopia. 



Seventh Nerve (Facial). 



Origin. The apparent origin of the seventh is from the up- 

 per end of the medulla in the groove between the olivary and 

 restiform bodies. Its deep origin is in the pons beneath the 

 floor of the fourth ventricle a little external to the nucleus of the 

 sixth. 



Course and Distribution. The seventh nerve passes out- 

 ward and forward with the auditory nerve (on its inner side) to 

 enter the internal auditory meatus. From their relative firmness 

 and texture and their close relation here, the seventh and eighth 

 nerves have been called respectively the portio dura and the 

 portio mollis. Running between them is a fasciculus from the 

 medulla known as the intermediary nerve of Wrisberg, or the 

 portio inter duram et mollem ; most of its fibers join the facial 

 in the internal auditory meatus. The facial nerve enters the 

 Fallopian aqueduct at the bottom of the meatus and follows 

 it to issue at the stylo-mastoid foramen, run forward in the sub- 

 stance of the parotid gland and divide behind the ramus of the 

 jaw into temporo-facial and cervico -facial branches. 



Its branches of communication are numerous, (i) In the in- 

 ternal auditory meatus it communicates with the auditory nerve ; 

 (2) in the aqiieductus Fallopii with the otic and spheno-palatine 

 ganglia, with the sympathetic and with the auricular branch of 

 the pneumogastric; (3) after leaving the stylo-mastoid foramen, 

 with the fifth, ninth, tenth and sympathetic. 



Its branches of distribution are also quite numerous, (i) In 

 the aqueductus Fallopii it gives off (a) the tympanic branch to 



