592 THE VEINS 



The basilar system consists of tlie following: 



The cavernous sinuses (S. cavernosi) lie in the inner grooves of the root of the 

 temporal wings of the sphenoid bone at either side of the sella turcica. The two 

 are connected by a wide traverse branch (Sinus intercavernosus) behind and 

 below the posterior part of the pituitary body. Each is continuous in front with 

 the ophthalmic vein and below with the inferior petrosal sinus. The third, sixth, 

 and the ophthalmic and maxillary divisions of the fifth nerve lie along the outer 

 wall of the sinus. The internal carotid artery traverses the sinus and is connected 

 with its fellow by a transverse branch which lies in the corresponding part of the 

 sinus. An oval opening in the floor communicates with the inferior petrosal sinus 

 and transmits the internal carotid artery. 



The sinus is not subdivided by strands of fibrous tissue as in man, but a few delicate bands 

 attach the artery to its wall. 



The inferior petrosal sinuses (S. petrosi inferiores)^ lie along the borders of 

 the basilar part of the occipital bone, inclosed in the thick dura which closes the 

 foramen lacerum. The anterior part extends about half an inch (ca. 12 mm.) 

 under the temporal wing of the sphenoid. Here communications exist with veins 

 in the pterygo-palatine fossa. The posterior end is bulbous and lies in the condy- 

 loid fossa; it communicates with the condyloid vein issuing from the hypoglossal 

 foramen and is drained by the inferior cerebral vein; it also receives an emissary 

 vein from the parieto-temporal canal. The roof of the sinus is perforated by an 

 oval opening at the carotid notch which opens into the cavernous sinus and trans- 

 mits the internal carotid artery; the latter forms the first bend of its S-shaped 

 curve in the petrosal and the second in the cavernous sinus. 



The basilar plexus (Plexus basilaris) is a venous plexus situated on the upper 

 surface of the basilar part of the occipital bone. It is connected through the hypo- 

 glossal foramen with the inferior petrosal sinus and communicates behind with the 

 spinal veins. 



The Veins of the Cranium 



The veins of the brain (Venae cerebri) do not in general accompany the cerebral 

 arteries. They have very thin walls, no muscular coat, and no valves. They are 

 arranged in two sets, superficial or cortical and deep or central. The superficial 

 veins are more numerous and larger than the arteries. They lie on the surface of 

 the brain in the pia mater and the subarachnoid space. 



The superior cerebral veins drain the upper and outer part of the cerebral 

 cortex. They receive veins from the medial surfaces of the hemispheres and open 

 into the superior sagittal sinus. Their terminal parts are bulbous and their open- 

 ings are directed obliquely forward, ^. e., contrary to the direction of the blood- 

 stream in the sinus. 



The inferior cerebral veins lie on the inferior and external aspect of the hemi- 

 spheres. They open into the inferior system of sinuses. The middle cerebral 

 vein runs in the lateral fissure (of Sylvius) and opens into the cavernous sinus. 



The deep cerebral veins issue from the central or ganglionic parts of the brain 

 at the transverse fissure. They converge to form the great cerebral vein (of Galen) 

 (V. magna cerebri). This passes upward and backward behind the splenium of 

 the corpus callosum and is continued as the straight sinus to join the sagittal sinus. 



The superior cerebellar veins ramify on the upper surface of the cerebellum. 

 They open into the superior system of sinuses and the great cerebral vein. The 

 inferior cerebellar veins are larger and go chiefly to the basilar plexus. The veins 

 of the medulla and ])ons end in the inferior system of sinuses. 



The meningeal veins (Vense meningese) arise in capillary plexuses in the super- 

 ficial and deep faces of the dura mater. Some end in the sinuses of the dura, 

 others accompany the meningeal arteries. 



' These are termed by Chauveau and M'Fadyean the subsphenoidal confluents. 



