LATERAL SINUSES. 



339 



Fig. 162." 



extremity of the sagittal suture 

 the parietal veins, from the peri- 

 cranium and scalp. Examined 

 in its interior, it presents numer- 

 ous transverse fibrous bands (tra- 

 beculae), the chorda? Willisii, 

 which are stretched across its 

 inferior angle; and some small 

 white granular masses, the glan- 

 duloe Pacchioni ; the oblique 

 openings of the cerebral veins, 

 with their valve-like margin, are 

 also seen on the walls of the 

 sinus. 



The termination of the supe- 

 rior longitudinal sinus in the two 

 lateral sinuses forms a considera- 

 ble dilatation, into which the straight sinus opens from the front, and the 

 occipital sinuses from below. This dilatation is named the torcular 

 Herophili^ and is the point of communication of six sinuses, the superior 

 longitudinal, two lateral, two occipital, and the straight. 



The Inferior longitudinal sinus is situated in the free margin of the falx 

 cerebri ; it is cylindrical in form, and extends from near the crista galli to 

 the anterior border of the tentorium, where it terminates in the straight 

 sinus. It receives in its course several veins from the falx. 



The Straight or fourth sinus is the sinus of the tentorium ; it is situated 

 at the line of union of the falx with the tentorium ; is prismoid in form, 

 and extends across the tentorium, from the termination of the inferior lon- 

 gitudinal sinus to the torcular Herophili. It receives the vense Galeni, 

 the cerebral veins from the inferior part of the posterior lobes, and the 

 superior cerebellar veins. 



The Occipital sinuses are two canals of small size, situated in the at- 

 tached border of the falx cerebelli ; they commence by several small veins 

 around the foramen magnum, and terminate by separate openings in the 

 torcular Herophili. They not unfrequently communicate with the termi- 

 nation of the lateral sinuses. 



The Lateral sinuses, commencing at the torcular Herophili, pass hori 

 zontally outwards, in the attached margin of the tentorium, and then curve 

 downwards and inwards along the base of the petrous portion of the tem- 

 poral bone, at each side, to the foramina lacera posteriora, where they ter 

 minate in the internal jugular veins. Each sinus rests in its course on the 

 transverse groove of the occipital bone, posterior inferior angle of the 

 parietal, mastoid portion of the temporal, and again on the occipital bone. 

 They receive the cerebral veins from the inferior surface of the posterior 



* The sinuses of the upper and back part of the skull. 1. The superior longitudinal 

 sinus. 2, 2. The cerebral veins opening into the sinus from behind forwards. 3. The 

 falx cerebri. 4 The inferior longitudinal sinus. 5. The straight or fourth sinus. 6. 

 The vena? Galeni. 7. The torcular Herophili. 8. The two lateral sinuses, with the 

 occipital sinuses between them. 9. The termination of the inferior petrosal sinus of 

 me sjde. 10. The dilatations corresponding with the jugular fossae. 11. The internal 

 jugular veins. 



f Torcular (a press), from a supposition entertained by the older anatomists that the 

 Columns of blood, coming in different directions, compressed each other at this poittt 



