890 



THE NERVOUS SYSTEM 



bones, with the angular veins. Two pass through the parietal foramina and establish 

 communications with the occipital veins, and a fourth, which is very inconstant, pierces 

 the occipital protuberance and joins the tributaries of the occipital veins. Connecting 

 each lateral sinus with the extracranial veins there are, as a rule, two emissary veins :- 

 one, the mastoid emissary vein, which passes through the mastoid foramen to the 

 occipital or posterior auricular vein; and the other, the post-condyloid vein, which 

 traverses the condyloid (posterior condyloid) foramen and joins the suboccipital 

 plexus. The cavernous sinus is in communication anteriorly with the superior 

 ophthalmic vein, and through the latter with the angular vein; it is connected 

 with the pterygoid plexus by emissary veins which pass either through the fora- 

 men ovale or the foramen Vesalii, and with the pharyngeal plexus by small 

 venous channels which accompany the internal carotid artery through the carotid 

 canal. 



FIG 662. SHOWING BLOOD-VESSELS OF CRANIAL DURA MATER AND CRANIAL NERVES IN THE 



BASE OF THE SKULL. 

 (On the left side the dura mater has been removed in the middle fossa.) 



Meningeal branch of 

 anterior elhuKiidal artery 



Meningeal branch of pos- 

 terior etltmotdtii 'iiii. 



artery 

 OPHTHALMIC 



Hn-lsl<>\ HI' 



THIRD SERVE 



CfNrr/*'"/A- .v'"".v 



TSOCIII.KJK XKltrn 



AUDIT! >l:Y AMI 



FACIAL -\7-.7; I 'AX 



Superior petrriKitl .vm</,v 



Inferior petrvx'tl tiuus 



Petrif-sijitii/ii'tiix A-/////.V 



SPIXM. M-l-l-:s- 



sour 



Posterior m __ 



branch of vertebral 

 artery 



Lf-fl marginal sinus 



Left lateral sinus 

 Superior sagittal sinus 



Cii rnltir sinus 

 CarOtfd artery 



ABDUCENS 



Basilar ui-ti'i'y 



/iVm/cr //!< .< \ 'if ft //;.v 



A nditoi it <nii ry 



GLOSSO-PHAHY.VdKAL 

 AND VAUr* M-:i:\ IS 

 Ant, rior ','1,1'if i 

 IIYl'OGLOSSAL 



KEK I /. 



SPINAL ACCES- 

 SORY NE&VM 



Right marginal tiinis 



Sight transverse s 



The Venous Lacunae or spaces are small clefts lined by endothelium which com- 

 municate with the meningeal veins and with blood sinuses. They also have com- 

 munications with the emissary veins and the diploic veins. They lie between the 

 outer and inner layers of the dura mater, the majority of them at the sides of the 

 superior sagittal sinus, but others are found in the tentorium associated with the 

 transverse sinuses and the straight sinus. 



Vessels. The blood supply of the cranial dura mater is derived from the meningeal arteries 

 winch ramify in it.s outer layer. The more important of these arteries have already been described 

 in the account of the vascular system, and it is only necessary here to recall the fact that tin- 

 greater part of the dura mator above the tentorium cerebelh is supplied by branches of the 

 middle meningeal arteries. These are reinforced (1) at the vertex by branches of the occipital 

 arteries which enter through the parietal foramina: C2) in the middle fossa by the small meniiwal 

 arteries and by meningeal branches of the internal carotid, lachrymal, and ascending pharymreal 

 arteries; and (3) in the anterior fossa by meningeal branches of the anterior and posterior 

 ethmoidal arteries. 



