602 



THE BLO OD- VA ,S'<" ULA R 8 YKTEM. 



The Superior Longitudinal Sinus occupies the attached margin of the falx 

 cerebri. Commencing at the foramen caecum, through which, in the child, it con- 

 stantly communicates by a small branch with the veins of the nasal fossae, it runs 

 from before backward, grooving the inner surface of the frontal, the adjacent 

 margins of the two parietal, and the superior division of the crucial ridge of the 

 occipital bone, and terminates by opening into the torcular Herophili. The sinus 

 is triangular in form, narrow in front, and gradually increases in size as it passes 

 backward. On examining its inner surface it presents the internal openings of the 

 superior cerebral veins, which run, for the most part, from behind forward, and 

 open chiefly at the back part of the sinus, their orifices being concealed by fibrous 

 folds ; numerous fibrous bands (chordce Willisii} are also seen, extending transversely 

 across the inferior angle of the sinus: and, lastly, some small, white, Drojecting 

 bodies, the glandulce Pacckioni. This sinus receives the superior cerebral veins, 

 numerous veins from the diploe and dura mater, and, at the posterior extremity 

 of the sagittal suture, veins from the pericranium, which pass through the parietal 

 foramina. 



The torcular Herophili, or confluence of the sinuses, is the dilated extremity of 

 the superior longitudinal sinus. It is of irregular form, and is lodged on one side 

 (generally the right) of the internal occipital protuberance. From it the lateral 

 sinus of the side to which it is deflected is derived. It receives also the blood from 

 the occipital sinus. 



The Inferior Longitudinal Sinus, more correctly described as the inferior l</m/i 

 tudinal vein, is contained in the posterior part of the free margin of the falx 

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

 terminates in the straight sinus. It receives several veins from the falx cerebri. 

 and occasionally a few from the mesial surface of the hemispheres. 



The Straight Sinus is situated at the line of junction of the falx cerebri with 

 the tentorium. It is triangular in form, increases in size as it proceeds backward, 

 and runs obliquely downward and backward from the termination of the inferior 

 longitudinal sinus to the lateral sinus of the opposite side to that into which the 

 superior longitudinal sinus is prolonged. It communicates by a cross branch 



Torcular herophiti. 



Foramen arcum. 



FIG. 326. Vertical section of the skull, showing the sinuses of the dura mater. 



with the torcular Herophili. Beside the inferior longitudinal sinus, it receives 

 the venae Galeni and the superior cerebellar veins. A few transverse bands cross 

 its interior. 



The Lateral Sinuses are of large size, and are situated in the attached inargin 

 of the tentorium cerebelli. They commence at the internal occipital protuberance. 



