THE NERVOUS SYSTEM 



1477 



however, being inconstant, the emissary veins referred to are 

 sometimes awanting. 



The name ' lateral ' or ' transverse ' is strictly applicable only to 

 that part of the sinus which is contained within the attached border 

 of the tentorium cerebelli, and extends from the internal occipital 

 protuberance to the postero- inferior angle of the parietal bone. 

 Beyond this latter point the sinus is known as the sigmoid sinus. 



Fi(»itat Air-Sinus 



Anterior Fossa 



Optic Nerve ^^^ ^^ 

 balmic Artery 



Third Nerve 



Fourth Nerve ~ri-,'L_^ 



Region of 

 Meckel's Cave 1 4 



Fifth Nerve TTI" 



Facial Nerve 



iiditory Nerve 



so-pharyngeal 



Nerve 

 ?neumogastric 

 Nerve 



Sylvian Border of Small 

 Wing of Sphenoid 



Ant, Pt. of Circ. Sinus 



' (Ant. Intercav. Sinus) 



Pituitary Body 



Cavernous Siniis 

 \\_.- Sixth Nerve 



Middle Foss.-, 



Basilar Sinus 

 Sup. Petrosal 

 Sinus 

 r\~ Inf. Petrosal 



Sinus 

 -> — Lateral Sinus 



Cerebellar Fossa 



Lateral Sinus 



Spinal Accessory Nerve 



Hypoglossal Nerve 



Spinal Cord 

 Occipital Sinus 



Cerebral Fossa 

 Torcular Herophili 



Fig. 617. — The Internal Base of the Skull, showing the Crania:. 

 Nerves and Venous Sinuses. 



The occipital sinus is situated within the falx cerebelli along its 

 attachment to the internal occipital crest. It is of small size, and is 

 formed inferiorly by the union of the two marginal sinuses (inferior 

 occipital) which lie on either side of the vermiform fossa and foramen 

 magnimi, where they communicate with the posterior intraspinal 

 veins and the terminal part of each lateral sinus. Superiorly it 



In certain cases the marginal 



opens into the torcular Herophili. 



