THE SINUSEi 



the inferior sagittal sinus, it receives the great cerebral vein (great vein of Galen) 

 and the superior cerebellar veins. A few transverse bands cross its interior. 



The transverse sinuses (sinus transversus; lateral sinuses) (Figs. 569, 570) are 

 of large size and begin at the internal occipital protuberance ; one, generally the 

 right, being the direct continuation of the superior sagittal sinus, the other of the 

 straight sinus. Each transverse sinus passes lateralward and forward, describing 

 a slight curve with its convexity upward, to the base of the petrous portion of 

 the temporal bone, and lies, in this part of its course, in the attached margin of 

 the tentorium cerebelli; it then leaves the tentorium and curves downward and 



Levator palpebroe 



Rectus superior 



Sup. oph- 

 thalmic vein 



Sphenoparietal 

 sinus 





End of straight sinus' Vertebral artery 



Superior sagittal sinus 

 FIQ. 570. The sinuses at the base of the skull. 



medialward to reach the jugular foramen, where it ends in the internal jugular 

 vein. In its course it rests upon the squama of the occipital, the mastoid angle 

 of the parietal, the mastoid part of the temporal, and, just before its termination, 

 the jugular process of the occipital ; the portion which occupies the groove on the 

 mastoid part of the temporal is sometimes termed the sigmoid sinus. The trans- 

 verse sinuses are frequently of unequal size, that formed by the superior sagittal 

 sinus being the larger; they increase in size as they proceed from behind forward. 

 On transverse section the horizontal portion exhibits a prismatic, the curved 

 portion a semicylindrical form. They receive the blood from the superior petrosal 

 42 



