42 A MANUAL OF ANATOMY. 



The right lateral sinus usually receives the superior 

 longitudinal sinus; while the left receives the straight 

 sinus, and the two are connected by a short sinus across 

 the internal occipital protuberance. 



In other cases the four sinuses open into a common 

 cavity termed the torcular Herophili or the confluence of 

 sinuses. The lateral sinuses also receive the veins from 

 the posterior part of the cerebrum, the upper and lower 

 surfaces of the cerebellum, from the diploe, also the su- 

 perior petrosal sinuses. They communicate with external 

 veins through the mastoid and posterior condyloid fora- 

 mina. 

 The Superior Petrosal Sinus. Diags. I and 2. 



Two in number, one on either side. This sinus is 

 located in a groove along the upper margin of the petrous 

 portion of the temporal bone (the tentorium being attached 

 to the margins of the groove). Externally it opens into 

 the lateral sinus, and internally into the cavernous sinus. 

 The Occipital Sinus. Diags. I and 2. 



Is formed by the junction of the marginal sinuses at the 

 posterior part of the foramen magnum. It extends upward 

 in the median line to open into the confluence of sinuses 

 over the internal occipital crest. The marginal sinuses 

 communicate in front with the lateral sinuses. 



The Inferior Petrosal Sinus. (A paired sinus.) Diags. I 



and 2. 



It extends backward from the cavernous sinus, at the 

 margin of the basilar process of the occipital bone, to 

 leave the skull through the anterior compartment in the 

 jugular foramen, and below the margin of the foramen helps 

 to form the internal jugular vein by joining with the lateral 

 sinus. 



