654 



THE BLOOD-VASCULAR SYSTEM 



vein and sinus. (/) The flow of blood in the sinuses is further retarded by the 



trabeculae stretching across their lumen, and in the sagittal sinus by the blood 



having to ascend, when the body is erect, through the anterior half of its course. 



The veins of the brain may be divided into the cerebral and the cerebellar. 



Fig. 517. — The Veins of the Brain, Superior Surface. (After Toldt, "Atlas of Human 

 Anatomy," Rebman, London and New York.) 



Superior sagittal sinus ^ 



Lateral protrusion 

 (lacuna) of supenor 

 sagittal sinus (.m- 

 jected) 



^ Superior cerebral veins 



Lateral lacuna of su- 

 penor sagittal sinus 



(opened) 



Arachnoidal 

 (Pacchionian) 

 granulations 



Superior cere- ,^ 

 bral veins 



Lateral lacuna of superior sagit- 

 tal sinus (opened) 



Venous orifice 



The Cerebral Veins 



The cerebral veins, like the cerebral arteries, may be divided into the cortical 

 and the central. 



The cortical or superficial veins ramify on the surface of the brain and return 

 the blood from the cortical substance into the venous sinuses. They lie for the 

 most part in the sulci between the gyri, but some pass over the gyri from one sulcus 

 to another. They consist of two sets: a superior and an inferior. 



(1) The superior cerebral veins [vena) cerebri superiores] (fig. 517), some eight to twelve in 

 number on each side, are formed by the union of branches from the convex and medial surfaces 

 of the cerebrum. Those from the convex surface pass medially and forward toward the 

 longitudinal fissure, where tluiy arc joined l)y the branches coming from the medial surface. 

 After receiving a sheath from the arachnoid, they enter obliquely into the superior sagittal 



1 



