658 



THE VEIN8. 



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

 foramen. 



The torcular Herophili 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 longi 

 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 herophili. 



Foramen csecum. 



FIG. 383. 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 margin 

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

 the one, generally the right, being the direct continuation of the superior longi- 

 tudinal sinus, the other of the straight sinus. They pass horizontally outward 

 to the base of the petrous portion of the temporal bone, then curve downward and 

 inward on each side to reach the jugular foramen, where they terminate in the 

 internal jugular vein. Each sinus rests, in its course, upon the inner surface of 

 the occipital, the posterior inferior angle of the parietal, the mastoid portion of the 

 temporal, and on the occipital, again just before its termination. These sinuses 

 are frequently of unequal size, that formed by the superior longitudinal sinus being 

 the larger, and they increase in size as they proceed from behind forward. The 

 horizontal portion is of a triangular form, the curved portion semicylindrical. 

 Their inner surface is smooth, and not crossed by the fibrous bands found in the 

 other sinuses. These sinuses receive the blood from the superior petrosal sinuses 

 at the base of the petrous portion of the temporal bone, and they unite with the 

 inferior petrosal sinus, just external to the jugular foramen, to form the internal 



