ARACHXOJD—J'IA MA TKR 



077 



Retzius) are at tlio cxtreniitie^ of the reces?;us laterales of the fourth ventricle, 

 behind the upper roots of the glos.so-pharyngeal nerves. Another large space, the 

 cisterna pontis, is continued from tlie anterior sul)ara(hnoid space of the cord, and 

 extends forwards as far as the commencement of the great l(jngitu<linal fissure, and 

 laterally to the inner margins of the temi)oro-sphenoidal lobes. The ))asilar artery 

 and the circle of Willis are placed in this space. The cisterna })ontis communicates 

 freely around the medulla oblongata with the cisterna magna — thus the medulla is 

 encircled Ijy a wide subarachnoid space. 



A large space is also to be found between the lower edge of the falx cerebri 

 fwhere the arachnoid passes across from one cerel)ral hemisphere to the other) and 

 tlie upper surface of the corpus callosum. This space contains the trunks and 

 larger branches of the anterior cerebral arteries. Another considerable space 



Fig. 407. — Cranial Nerves ix the Base of the Skill. 

 (On tlie left side the dura mater has bt-eu removed iu the middle fossa.) 



Meningeal branch of 

 aiite.rior ethmoidal arteru 



Meningeal branch of ]>us- 

 teriur ethmoidal artery 



Middle meningeal 

 arteru 



OPJfr/f.iLV/r 



Divisioy OF 



FIFTH m:r\e 



THIRD XERVE — 



Carernous sinus 

 FOrnTII SFRVF 

 AVDinjRY ASH 

 FACIAL SERVES 

 Superior petrosal simis 

 Inferior petrosal sin us 

 Pelro-sqiiamotis sinus 

 SI'ISAL ACCES- 

 SORY SERVE 

 Sigmoi'l portion of 

 lateral sinus 

 Posterior meningeal 

 branch of vertebral 

 artery 

 Left marginal sinus 



Left lateral sinus 

 Superior longitudinal sinus 



< irci'liir sinus 

 Carotid artery 



SIXTH ni:rve 



Basilar artery 

 Basilar plexus of veins 

 Auditory artery 



rerlehral artery 

 QU) SSO- PH.\ R r.VG FA L 

 AXU PXElWrjOASTRir 



Anterior niiinnt artery {S. 



HYPOGLOSSAL 



SERVE 

 SPISA L A crES- 

 SORY SERVE 



Riiiht mnrip,,,'! .;.,„5 



tjceijiital siii^ 



,l,t Inl^riil xi 



-exists in the fissure of Sylvius, and in this the middle cerebral artery ramifies. 

 Thus, with the exception of the cisterna magna, all these spaces serve for the 

 accommodation of large arteries. There is also a space between the corpora (juadri- 

 geinina and the anterior extremity of tlie suiierior vermiform process of the yere- 

 bellum, and through this the veins of (ialen pass to terminate in the straight sinus. 



The PIA MATER is a delicate vascular membrane wliich closely invests the 

 nervous sul)stance. It follows accurately the contour of the surface of tlie lirain, 

 dipping into all the fissures of the cerebrum and cerebellum — in the smaller sulci 

 of the latter, however, a double layer cannot be distinctly made out. Processes or 

 folds of this membrane project into some of the ventricles of tlie brain, and are 

 separated from the ventricular cavities only l)y a layer of epitheliuuL These 

 folds form the velum interpositum and choroid plexuses, which will be described 



