CHAP.X.] SINUSES OF THE DURA MATER. 251 



collect the blood from all parts of the cranium. These canals, sinuses 

 of the dura mater, receive likewise the venous blood of the brain. The 

 largest sinuses are the superior longitudinal and the lateral sinuses. 

 The former extends along the convex edge of the falx cerebri, com- 

 mencing very small by receiving veins from the ethmoid and frontal 

 bones, and terminates in a reservoir common to it and other sinuses 

 at the internal occipital protuberance (torcular Herophili). It thus 

 serves to collect blood from the superior and lateral parts of the 

 dura mater, from the vault of the cranium, and from the hemi- 

 spheres of the brain ; the veins of the latter entering it obliquely 

 forwards. The lateral sinuses are lodged in tortuous furrows, which 

 mark the occipital, the parietal, and the temporal bones. They 

 are two in number, and extend on each side from the torcular 

 Herophili to the jugular foramen, where they are continued into 

 the internal jugular veins. These sinuses serve not only to carry 

 into the jugular veins all the blood which is poured into the tor- 

 cular, but likewise to receive blood from the lateral and posterior 

 parts of the dura mater and cranium, from the inferior surface 

 of the posterior lobes of the brain, and from the cerebellum. A 

 short sinus, also of considerable width, is lodged in the tentorium 

 cerebelli. This is the straight sinus ; it passes from before back- 

 wards, occupying about the middle of the vault of the tentorium, 

 and opening behind into the torcular. It receives blood from the in- 

 terior of the brain by two large veins, the vena mayna Galeni. The 

 cavernous sinuses, two in number, lie one on each side of the sella 

 Turcica, from which the internal carotid arteries separate them. 

 Their irregular shape is rather that of reservoirs than of canals 

 They receive the ophthalmic veins from the orbit, as well as nume- 

 rous small veins from the cranial bones, the dura mater, and the 

 anterior and middle lobes of the brain. 



Other small sinuses are met with which serve chiefly to establish 

 a communication between those above-mentioned, while at the same 

 time they receive some blood from the neighbouring textures. The 

 petrosal sinuses, two on each side, superior and inferior, pass between 

 the cavernous and lateral sinuses : the transvwse sinus runs between 

 the petrosal and cavernous sinuses of opposite sides ; and the cir- 

 cular or coronary sinus, while it receives blood from the pituitary 

 body and from the sphenoid bone, connects together the cavernous 

 sinuses in front, and thus completes the venous circle around the 

 sella Turcica. 



We see, in this arrangement of venous canals, a beautiful pro- 

 vision agaiiist the effects of undue venous congestion within the 



