240 



HEAD AND NECK 



86, 92). It lies upon the lateral aspect of the body of the 

 sphenoid, and, for the greater part of its course, it'traverses the 

 cavernous sinus. It emerges from the carotid canal into the 

 foramen lacerum at the apex of the petrous hone ; then it passes 

 through the upper part of the foramen lacerum, pierces the outer 

 layer of dura mater, and enters the middle cranial fossa, at the 



Infundibulum 



Abducens nerve 

 Trigeminal nerve 



Trochlear ner 



Acoustic and 

 facial nerves 



Glosso-pharyn- 

 geal nerve 



Accessory nerve 



Section throu 

 the medulla 

 oblongata 



Transverse sinus 



Optic nerve 



nternal carotid 

 artery 



|A Posterior 

 J*.V- communicating 

 B\ artery 



' *' Oculo-motor nerve 



Posterior cerebra 



artery 

 Superior 

 cerebellar arter 

 Tentorium 



Basilar 

 artery 



Vertebral 

 artery 



Superior petro.- 

 sinus 



Transverse sir 



Occipital sinus 



Superior sagittal sinus 



Straight sinus (divided) 



FlG. 88. Floor of the Cranium after the removal of the Brain and the 

 Tentorium Cerebelli. The blood vessels forming the circulus arteriosus 

 have been left in place. 



root of the posterior clinoid process ; there it bends, at right 

 angles, and passes forwards to the lower root of the small wing 

 of the sphenoid, where it turns abruptly upwards and pierces 

 the inner layer of the dura mater, immediately posterior to 

 the entrance of the optic nerve into the optic foramen and 

 on the medial side of the anterior clinoid process. It was 

 severed at that point during the removal of the brain ; but it 

 will be afterwards seen to end, on the basal aspect of the 



