372 LATERAL SINUSES. 



tation is named the torcular Herophili,* and is the point of communica- 

 tion of six sinuses, the superior longitudinal, two lateral, two occipital 

 and the straight. 



The Inferior longitudinal sinus is situated in the free margin of the 

 falx cerebri ; it is cylindrical in form, and extends from near the 

 crista galli to the anterior border of the tentorium, where it terminates 

 in the straight sinus. It receives in its course several veins from the 

 falx. 



The Straight or fourth sinus is the sinus of the tentorium ; it is 

 situated at the line of union of the falx with the tentorium; is 

 prismoid in form, and extends across the tentorium, from the termination 

 of the inferior longitudinal sinus to the torcular Herophili. It receives 

 the venae Galeni, the cerebral veins from the inferior part of the pos- 

 terior lobes, and the superior cerebellar veins. 



The Occipital sinuses are two canals of small size, situated in the 

 attached border of the falx cerebelli ; they commence by several 

 small veins around the foramen magnum, and terminate by separate 

 openings in the torcular Herophili. They not unfrequently communi- 

 cate with the termination of the lateral sinuses. 



The Lateral sinuses, commencing at the torcular Herophili, pass 

 horizontally outwards, in the attached margin of the tentorium, and 

 then curve downwards and inwards along the base of the petrous 

 portion of the temporal bone, at each side, to the foramina lacera 

 posteriora, where they terminate in the internal jugular veins. Each 

 sinus rests in its course upon the transverse groove of the occipital 

 bone, posterior inferior angle of the parietal, mastoid portion of the 

 temporal, and again on the occipital bone. They receive the cerebral 

 veins from the inferior surface of the posterior lobes, the inferior 

 cerebellar veins, the superior petrosal sinuses, the mastoid, and posterior 

 condyloid veins, and at their termination, the inferior petrosal sinuses. 

 These sinuses are often unequal in size, the right being larger than the 

 left. 



The sinuses of the base of the skull are the 



Cavernous, 

 Inferior petrosal, 

 Circular, 



Superior petrosal, 

 Transverse. 



The Cavernous sinuses are named from presenting a structure similar 

 to that of the corpus cavernosum penis. They are situated on each 

 side of the sella turcica, receiving, anteriorly, the ophthalmic veins 

 through the sphenoidal fissures, and terminating posteriorly in the in- 

 ferior petrosal sinuses. In the internal wall of each cavernous sinus is 



* Torcular (a press), from a supposition entertained by the older anatomists 

 that the columns of blood, coming in different directions, compressed each other 

 at this point. 



