THE SINUSES OF THE DURA MATER 



655 



fibrous bands (chordae Willisii) extend transversely across the inferior angle of 

 the sinus; and, lastly, small openings communicate with irregularly shaped venous 

 spaces (venous lacunas) in the dura mater near the sinus. There are usually three 

 lacunae on either side of the sinus : a small frontal, a large parietal, and an occipital, 

 intermediate in size between the other two (Sargent 1 ). Most of the cerebral 

 veins from the outer surface of the hemisphere open into these lacunae, and numer- 

 ous arachnoid granulations (Pacchionian bodies) project into them from below. 

 The superior sagittal sinus receives the superior cerebral veins, veins from the diploe 

 and dura mater, and, near the posterior extremity of the sagittal suture, veins from 

 the pericranium, which pass through the parietal foramina. 



The numerous communications exist between this sinus and the veins of the 

 nose, scalp, and diploe. 



Great cerebral vein 



Glossopharynyeal nerve 



Vaijus nerve 

 Accessory nerve 



Acmislic nerve 



Facial nerve 



Abducent nerve Trigeminal nerve 



FIG. 567. Dura mater and its processes exposed by removing part of the right half of the skull, and 



the brain. 



The inferior sagittal sinus (sinus sagittalis inferior; inferior longitudinal sinus) 

 (Fig. 567) is contained in the posterior half or two-thirds of the free margin of the 

 falx cerebri. It is of a cylindrical form, increases in size as it passes backward, and 

 ends in the straight sinus. It receives several veins from the falx cerebri, and 

 occasionally a few from the medial surfaces of the hemispheres. 



The straight sinus (sinus rectus; tentorial sinus) (Figs. 567, 569) is situated at 

 the line of junction of the falx cerebri with the tentorium cerebelli. It is triangular 



1 Journal of Anatomy and Physiology, vol. xlv. 



