THE EXTREMITIES. 459 



anter. and poster., covers the fossa pro gland, pituitar., presenting 

 in the middle a foramen for infandibul. and sin. circular Ridleyi. 



b. Between the apex of the petrous and the ala parva of sphe- 

 noid bone, the superior external wall of sin. cavernos., and farther 

 outwards the sin. ophthalmicus is formed. 



c. Tubular sheaths for vessels and nerves penetrate the fora- 

 mina of the basis cranii. 



5. Sinus ; are found between the layers of the dura mater. 



a. Sinus transversi in the sulcus transvers., at the posterior 

 border of tentorimn cerebelli. Into it open 



I., Sinus longitud. super. ; passing along the convex border of 

 fafa cerebri ; opens into the right sin. transv. on the protube- 

 rantia occipit. interna. 



2. Sinus quartus ; [straight] passes into the centre of tento- 

 rium, from before backwards ; receiving where tentorium andfalx 

 cerebri unite, 



Vena rtiagna Galeni, which, arising by the confluence of vv. 

 cerebrates internee, pass into plexus choroid. 3. 



Its posterior extremity enters the left sinus, transversus (s. tor- 

 cular. Herophili). 



3. Sinus longitud, inferior, on the concave border offah cere- 

 bri, passes into sinus quartus. 



4. Sinus petrosus superior, in the sulcus petrosus on the supe- 

 rior angle of pars, petrosa ; unites sinus cavernos. with trans- 

 versus. 



5. Sinus petrosus infer., between the apex of pars petrosa and 

 the clivus ; opens at the forar/i. jugulare into the sinus trans- 

 versus. 



b. Sinus occipitalis posterior passes on the crista occipit. in- 

 terna, from the torcular Herophili downwards to the sinus circu- 

 lar, foram. magni, which lies upon the posterior boundary of 



foram. magn., and is connected with the so-called sin. occipit. ant. 

 s. basilar. upon the clivus and Ihe fossa pro medulla oblongata. 



c. Sinus cavernosi passes on both sides of sella turcica between 

 the apex of petrous and ala parva of sphenoid bone. Into it dis- 

 charge, 



1 . Sinus circularis Ridleyi ; surrounding the hypophysis ce- 

 rebri. 



2. Sinus spheno-parietaks s. ophthalmici (ant. extremity of sin. 

 cavernosi) ; at the inferior extremity of/ss. orbitalis superior. 



3. Sinus petrosi anteriores ; between pars squamosa and pe- 

 trosa of temporal bone (often wanting). 



II. Arachnoidea, surrounded by the Dura, it surrounds the pia 



