654 



ANGIOLOGY 



The Sinuses of the Dura Mater (Sinus Durse Matris). Ophthalmic Veins and 



Emissary Veins. 



The sinuses of the dura mater are venous channels which drain the blood from the 

 brain; they are devoid of valves, and are situated between the two layers of the 

 dura mater and lined by endothelium continuous with that which lines the veins. 

 They may be divided into two groups: (1) a postero-superior, at the upper and back 

 part of the skull, and (2) an antero-inferior, at the base of the skull. 



The postero-superior group comprises the 



Superior Sagittal. 

 Inferior Sagittal. 



Straight. 



Two Transverse. 



Occipital. 



Dural vein 



Superior sagittal 

 sinus 



Venous 

 lacuna 



Venous lacuna 



FIG. 566. Superior sagittal sinus laid open after remova of the skull cap. The chordae Willisii are clearly seen. 

 The venous lacunae are also well shown; from two of them probes are passed into the superior sagittal sinus. 

 (Poirier and Charpy.) 



The superior sagittal sinus (sinus sagittalis superior; superior longitudinal sinus] 

 (Figs. 566, 567) occupies the attached or convex margin of the falx cerebri. Com- 

 mencing at the foramen cecum, through which it receives a vein from the nasal 

 cavity, it runs from before backward, grooving the inner surface of the frontal, 

 the adjacent margins of the two parietals, and the superior division of the cruciate 

 eminence of the occipital; near the internal occipital protuberance it deviates to 

 one or other side (usually the right), and is continued as the corresponding trans- 

 verse sinus. It is triangular in section, narrow in front, and gradually increases in 

 size as it passes backward. Its inner surface presents the openings of the superior 

 cerebral veins, which run, for the most part, obliquely forward, and open chiefly 

 at the back part of the sinus, their orifices being concealed by fibrous folds ; numerous 



