7V//; CKAMAL lil'RA MAT Mi 



SS9 



and its inner bonier forms the boundary of the ]or<niu n <>] lln tlin /ilirni/inn ai-ll<i ami 

 surrounds I he ini'undibiihini. Its upper surface is in relation with the base of (lie 

 brain, and its lower surface is in relation with t he hypophysis, which it binds down 

 in the hypophyseal fossa. 



The spaces which lie between the layers of the cranial dura mater are Mockel's 



caves, the spaces which lod^e t heendolymph&ticaacs.and i hebloodnnuaesand lacuna-. 



Meckel's caves are two cleft-like spaces or niches which lie. one on each side, in 

 the triireininal impression on the apex of the petrous portion of the temporal bone. 

 Kach space lodges the semilunar (< .asserian) ganglion and the motor and sensory 

 roots of the trigeniinus of the corresponding side, and it communicates with the sub- 

 dural space in t he posterior fossa of the cranium by an oval opening, which lies abo\e 

 the superior border of the petrous portion of the temporal bone and below the supe- 

 rior, petrosal sinus. 



Fir.. <;<>!. -Siiowivi; THK I'l'i-Eit SI-RFACE OF THE TENTORIUM CEREBELLI AND THE TENTORIAL 



.N"li II IliK'iicn WHICH THK MlU-IIKAIN AM) 1'oSTERIOH CEREBRAL ARTERIES ENTER THE 



MIDDLE FOSSA OK THE CHAM CM. 



I.M I MilBULUM 



\*0m n^, 



CRIST* QALLI 

 OPTIC KER VE 



Sphtno-parielHl sinus 



01'TfC TRACT 



niu:i> XKRVE 



Cerebral peduncle 



-I'yic ' 



MEHK.WKril- 

 ALON 



Fair eerebri 



Tentorium cere belli 

 Straight sintts 



crrebral 

 Anterior cerebral 



nntni-' 



(':/> / -M.//.V .titnts 



'.r cerebellur 

 I>0sterivr cerebral 



Free border of ten- 



toriuni bounding 

 tentorinl notch 



Tranivcrif limit 



Superior tagittal sinus 



The space which contains the endolymphatic sac on each side lies behind the 

 petrous portion of the temporal bone and communicates with the aquseductus 



vestibuli. 



The venous sinuses and lacunae. The cranial blood sinuses have already been 

 fully described in the account of t lie vascular system, and it issuliicient to note here 

 that they are continuous, on the one hand, with the meningeal veins, and, on the other, 

 with the veins outside the cranial walls. The \essels which establish communication 

 between the blood sinuses and the extracranial veins are referred to collectively as 

 emissary veins. They possibly help to maintain the regularity of the cranial cir- 

 culation, and they have therefore a certain amount of practical importance. 



The sinuses which are connected with the extracranial veins by emissary veins 

 are the superior sagittal, the transverse (lateral), and the cavernous. Three or four 

 emissary veins pass from the superior sagittal sinus: one passes through the foramen 

 caecum and communicates with the veins of the roof of the nose, or, through the nasal 



