NERVES 151 



The 6xH or ABDUCENS OCULI. Origin Superficial: from 

 the sulcus between the pons and medulla, anterior to the 

 anterior pyramid. Deep : floor of 4th ventricle beneath 

 fasciculus teres. 



Course. Pierces dura mater on basilar process and grooves 

 side of dorsum ephipii to reach cavernous sinus; lies to 

 outer side of internal carotid, and below the other nerves. 

 Enters orbit by sphenoidal fissure, between the heads of the 

 external rectus, lying above ophthalmic vein. 



Distribution. External rectus (ocular surface). 



Relations. The following table shows how the nerves of the 

 orbit change their position to one another. They lie from 

 above down. 



In ^Cavernous /w ^ sphenoidal Fi , sure . 



Third. Fourth. Frontal. Lachrymal. 

 Fourth. (Above the muscles.) 



Fifth. Superior division o 



Sixth 



The 7TH or FACIAL. Origin Superficial : from the pons, ex- 

 ternally and posteriorly, on its ventral surface. Deep : floor 

 of 4th ventricle, anterior and external to nucleus of 6th nerve. 



Course. Passes forwards and outwards to enter the internal 

 auditory meatus ; it lies upon a groove on the auditory nerve, 

 with pars intermedia of Wrisberg between, and at the 

 bottom of the meatus the latter joins the facial, which 

 entering the aqueductus Fallopii, runs first outwards 

 above and between cochlea and vestibule as far as hiatus 

 Fallopii ; then backwards in internal wall of tympanum, just 

 above fenestra ovalis, at the bend presenting a swelling, the 

 geniculate ganglion ; and finally it passes downwards, to emerge 

 from the bone at the stylo-mastoid foramen ; it then passes 

 outwards and forwards in the parotid, dividing behind the 

 ramus of jaw into temporo-facial and cervico-facial branches, 

 which further subdivide and intercommunicate, forming the 

 pes anserimis. 



Communications : 



In the meatus, with auditory and pars intermedia. 



In the aqueduct, with Meckel's ganglion by large superficial 

 petrosal ; otic ganglion by small superficial petrosal ; plexus on 

 middle meningeal by external superficial petrosal. 



