THE HEAD AND NECK 



1075 



forms the outer wall of the cavernous sinus, a little in front of the 

 posterior clinoid process of the sphenoid bone. 



The fourth or trochlear nerve, of small size, pierces the dura mater 

 at a point a little behind the posterior clinoid process of the sphenoid 

 bone, external to the third nerve, and beneath the free margin of 



FzxHital Air-Sinus 



Optic Nerve-^ 

 ithalmic Artery 



Third Ner 



Fourth Nerve,/- ;]/ 



Region of J^ 

 Meckel's Cave ' 



Fifth Nerve 



Facial Nerve 



lUditory Nerve 



>so-phary ngeal . 



Nerve 

 Pneumogastric 

 Nerve 



Spinal Accessory 



Anterior Fossa 



Sylvian Border of Smai. 

 Wing of Sphenoid 



\ Ant. Pt. of Circ. Sinus 

 v\ , (Ant. Intercav. Sinus^ 

 V ^ Pituitary Body 



Cavernous Sinus 

 Sixth Nerve 



'^^V-^ i-'fr^ " Middle Fossa 



WaVL. w l..>-4l4i-- Basilar Sinus 



-v,-^--"^^_ ,- , I M Sinus 



'^'\^ '%."""""-'"^— M Inf. Petrosal 

 ' ' j Sinus 



->i- Lateral Sinus 



Cerebellar Fossa 



Lateral Sinus 



Cerebral Fossa 



Spinal Cord, ■' Torcular Herophili 

 Occipital Sinus 



Fig. 439, — The Internal Base of the Skull, showing the Cranial 

 Nerves and Venous Sinuses. 



the tentorium cerebelli. Thereafter it traverses the outer wall of 

 the cavernous sinus. 



The fifth or trigeminal nerve consists of two roots — sensory and 

 motor. These two roots pierce the dura mater at the apex of the 

 petrous part of the temporal bone, and enter a recess of the dura 

 mater, called Meckel s cave, where they will be presently described. 



The sixth or abducent nerve pierces the dura mater at the outer 

 border of the dorsum sellse of the sphenoid bone, a little below.the 



