VEX us SINUSES OF THE CBAMUM 



621 



Herophili when tliis is present. It receives in its course veins from the ten- 

 torium cerebelli, and from the inferior surface of the cerebelkun. It communi- 

 cates through the plexus of veins which surrounds the hypoglossal nerve in the 

 anterior condyloid foramen with the vertehral vein and veins of the anterior spinal 

 plexus. 



(5) The circular sinus, so called (fig. 387), is a venous plexus encircling the 

 hypophysis cerebri, and connecting the right and left cavernous sinuses. The more 

 distinct channels are found, one in front of the sella turcica, one behind, and one 

 on its floor, and are sometimes called the anterior, posterior, and inferior inter- 

 cavernous sinus, the last being also known as the inferior circular sinus of 

 W^inslow. 



(t) ) The transverse or basilar sinus (fig. 387) is a venous plexus in the sub- 

 stance of the dura mater over the basilar process of the occipital bone. It extends 

 from the cavernous sinus to the margin of the foramen magnum below. It 



Fig. 388. — The Venous Sinuses. (Longitudinal section.) 



rO UR TH XER VE THIRD NER VE 



Fall cerebri 



SECOND NERVE 



Superior loni/i- 

 tudinal xiiiu.i 

 Inferior lonr/i- 

 tudinal sinus 



Veins of Galen 



S!raight sinus 



Tentorium 

 cerebelli 



Lateral sinus — 



Superior 

 petrosal sinus 



Falx cerebelli 



SEVENTH AM) 

 KKiUTII 

 NERVES 



NINTH. TENTH. AND 

 ELEVENTH NERVES 



TWELFTH NERVE 



SECOND CERVICAL NERVE 



Ligamentum deutieulatum 



in-i II 



NERVE 



FTRST 

 CERVICAL 



NER I '£■ Inferior petrosal sin !m 



Vertebral 

 artery 



communicates laterally with the inferior petrosal sinus, and inferiorly with the 

 anterior spinal veins. Through this sinus passes the sixth nerve. One of the 

 larger of the irregular venous channels forming the sinus passes transversely 

 from one inferior petrosal sinus to the other. It is this portion to which tlie 

 description of the transverse sinus given by some authors ajtpears to apply. This 

 venous plexus on the basilar process is serially homologous with the anterior sj)inal 

 plexus of veins on the ])osterior surface of the bodies of the vertebra^. 



(7) The lateral sinus (fig. 387) extends from the internal occijntal protuber- 

 ance to the jugular foramen. In this course it lies in the groove (which has been 

 named after it) along the squamous portion of the occipital bone, the posterior 

 inferior angle of the parietal bone, the mastoid portion of the temporal bone, and 

 the jugular process of the occipital bone. It at first runs horizontally outwards 

 and forwards between the two layers of the tentorium cerebelli. following the curve 

 of the groove on the occipital and the posterior inferior angle of tlie parietal bones. 

 In this part of its course it is sometimes known as the transverse sinus, or 

 lateral sinus proper, but on reaching the groove in the mastoid portion of the tern- 



