ii4 THE NERVOUS SYSTEM 



The superior sagittal sinus passes backwards and, at the 

 posterior end of the falx cerebri, it reaches the internal occipital 

 protuberance, where it bends sharply, usually to the right, to 

 form the transverse (lateral) sinus. In its course, the superior 

 sagittal sinus receives numerous tributaries from the surface of 

 the brain and, through a foramen in each parietal bone, it 

 communicates with the veins of the scalp. Through this 

 connexion septic infections of the scalp may give rise to 

 thrombosis of the sinus. 



The Inferior Sagittal (Longitudinal) Sinus lies in the free, 

 lower border of the falx cerebri and, at its posterior end, 

 unites with the great cerebral vein (of Galen, p. 27) to 

 form the straight sinus. It receives tributaries from the 

 medial surfaces of the cerebral hemispheres. 



The Straight Sinus runs backwards over the upper surface 

 of the tentorium cerebelli in the lower border of the falx 

 cerebri, until it reaches the internal occipital protuberance, 

 where it bends sharply, usually to the left, to form the 

 transverse (lateral) sinus. It receives tributaries from the 

 occipital lobes and from the cerebellum. 



The Transverse (Lateral) Sinus of the right side is con- 

 tinuous with the superior sagittal sinus, while that of the left 

 side is continuous with the straight sinus. It begins at the in- 

 ternal occipital protuberance and runs laterally in the attached, 

 peripheral border of the tentorium cerebelli. When it reaches 

 the mastoid part of the temporal bone, it passes downwards, 

 forming a deep groove in the side wall of the posterior 

 cranial fossa. In this part of its course, the transverse sinus 

 lies behind the tympanic (mastoid} antrum, which is contained 

 within the posterior part of the petrous temporal, and it 

 communicates with the posterior auricular vein of the scalp 

 through the mastoid foramen. Finally, it passes through the 

 jugular foramen and becomes continuous with the internal 

 jugular vein. 



The transverse sinus is joined by the superior petrosal 

 sinus, which connects it to the cavernous sinus, and by 



