EMERGENT VEINS. 489 



The Superior longitudinal sinus, situated in the attachea 

 border of the falx cerebri, commences at the crista galli process, 

 and terminates at the ossific tentorium, in a reservoir termed the 

 torcular 'Herophili, or confluent of the sinuses, which bifurcates 

 and joins the lateral sinuses. 



The Inferior longitudinal sinus is small, and not always 

 present. It is situated in the lower part of the falx, below the 

 superior one, pursuing a similar course, and discharging into the 

 torcular Herophili. 



The Lateral sinuses, situated within the folds of the tento- 

 rium cerebelli, receive the blood from the longitudinal sinus, and 

 terminate in veins^ which empty themselves into the temporal 

 veins, through the parieto-temporal conduits. 



The Petrosal sinuses, situated at the sides of the petrosal 

 bone, form a communication between the parieto-temporal con- 

 fluents and the cavernous sinuses. 



The Cavernous sinuses are situated under the dura mater at 

 the sides of the sella turcica, and are united by an arched branch, 

 sometimes termed the transverse sinus, which winds round the 

 back of the pituitary gland ; posteriorly they open through the 

 foramen lacerum basis cranii into the subsphenoidal confluent. 

 Anteriorly these sinuses lead to the alveolar veins. 



The Occipital sinuses, which are very irregular, are situated 

 in the falx cerebelli, and terminate, through the condyloid fora- 

 mina, in the subsphenoidal confluent. 



emergent veins. 



The venous blood from the encephalic sinuses leaves the 

 cranium in various ways by the emergent vessels. These are 

 the Parieto-temporal and Subsphenoidal confluents, the Spinal 

 and Alveolar reins. 



The Parieto-temporal confluent occupies the conduit of 

 the same name, receiving the blood of the longitudinal and trans- 

 verse sinuses, and discharging into the temporal veins, which 

 arise chiefly in this confluent. 



The Subsphenoidal confluent lies along the side of the 

 basi-occipital and basi-sphenoid bones, terminating anteriorly in 

 a blind end. The cavernous sinus opens into it through the 

 foramen lacerum basis cranii, the internal carotid artery passing 

 through the orifice. Posteriorly it terminates as the anterior 



