620 



THE VEINS 



lower margin of that process to the junction of the falx with tlie tentorium, where 

 it ends in the straight sinus. The sinus is cylinch-ical in shape and of small size, 

 and receives some of the inferior frontal veins of the brain, some of the veins from 

 the median surface of the l)rain, and some of the veins of the falx. 



(3) The straight sinus, or sinus rectus (fig. 388) — also variously called the 

 sinus tentorii, perpendicularis, and obliquus — lies along the junction of the falx 

 cerebri with the tentorium cerebelli. It is formed by the union of the great vein of 

 CJalen, from tlie velum interpositum, and the inferior longitudinal sinus. It receives 

 in its course brandies from the tentorium cerebelli and from the upper surface of 

 the cerebellimi. It runs downwards and backwards to the internal occipital pro- 

 tuberance, where it ends in the left lateral sinus, at times in the right lateral sinus, 

 or in the torcular Herophili when that blood-space is present. On section it is 

 triangular in shape, Avith its apex upwards. 



Fig. 387. — The Venous Sinuses. 

 (From a dissection by "W. J. Walsliam iu St. Bartholomew's Hospital IMuseum.) 



Meningeal branch of 

 anleiior tlhmoidal artery 



Meninf/eul branch nf pos- 

 terior ethmoidal artery 



Middle meningeal 



arteni 



OPHTHALMIC 



DIVISIOX OF 



FIFTH NERVE 



THIRD NERVE 

 Cavernous sinus 

 FOURTH NERVE 

 AVniTORY AND 

 FAdAL NERVES 

 Sitpt'rior petrosal sin us 

 Inferior petrosal sintis _ 

 Pelro-sqnamous sinus 

 HPINAL ACCES- 

 SOR Y NER VE 

 Sigmoid portion 0/ 

 lateral sinus 

 Posterior meningeal 

 branch of vertebral 

 artery 

 Left marginal sinus 



Left lateral sinus 

 Superior longitudinal sinus 



Circular sinus 

 Carotid artery 

 SIXTH NERVE 

 Basilar artery 

 Rastlar plexus of reins 

 A udi/ory artery 



Terttliral arteri/ 

 GLOSSO-PHARYNOEAL 

 ASD PXEfMOGASTRIC 



Antfrinr spimil arteri/ [X. 



HYPOCLUSSAL 



NERVE 

 SPINAL ACCES- 

 SORY NERVE 



Right marginal sinus 

 Occipital sinus 

 Right lateral sinus 



(4) The occipital sinus (fig. 387) ascends mesially at the attached margin of 

 the falx cerel>elli, along tlie lower half of the squamous portion of the occipital 

 bone from near the posterior margin of the foramen magnum to the internal 

 occipital ]~>rotuberance. It usually begins in a right and a left branch, known as the 

 marginal sinuses. These proceed from the termination of each lateral sinus, run 

 round the foramen magnum, where they communicate with the posterior spinal 

 veins, and unite at a variable distance from the internal occii)ital protul)erance to 

 form the single occipital sinus. Sometimes they remain separate as far as the 

 occipital protuberance, then forming two occipital sinuses. One or other of the 

 marginal sinuses may be much smaller than the other, or be entirely absent. 

 At the point where the marginal sinuses unite to form the single occiiiital sinus, 

 there is a communication with the posterior spinal veins. The occijiital sinus 

 ends either in one of the lateral sinuses, in the straight sinus, or in the torcular 



