CRANIAL CAVITY. 



behind the ear. The superficial temporal drains the temporo- 

 parietal region and descends in front of the ear. The frontal 

 and supra-orbital drain the forehead and unite (angular vein) 

 at the inner canthus. [879] 



CRANIAL CAVITY. 

 MENINGES. 



The brain is enclosed, from without inward, by the dura, 

 arachnoidea, and pia. 



Dura Mater. This is a dense membrane, smooth internally 

 but rough externally, which is attached loosely to the vault, 

 except along the sutures, but firmly to the floor. In places 

 its layers separate to form venous sinuses. Four septa project 

 from its deep surface, viz.: The falx cerebri, sickle-shaped, 

 separates the cerebral hemispheres. It is narrow in front and 

 attached to the crista galli ; broad behind and attached to the 

 tentorium in the midline, enclosing the straight sinus; convex 

 above and attached to the vault, enclosing the superior longi- 

 tudinal sinus; and concave and free below, enclosing the in- 

 ferior longitudinal sinus. [597] 



The tentorium cerebelli, crescentic and horizontal, separates 

 the cerebrum and cerebellum. It is convex behind and at- 

 tached to the occipital, enclosing the lateral sinuses; attached 

 laterally to the parietal and, enclosing the superior petrosal 

 sinus, the superior border of the petrous bone; and free and 

 concave (incisura tentorii) anteriorly. Prolongations of the 

 free and attached margins cross beyond the apex of the petrous 

 bone and are attached respectively to the anterior and posterior 

 clinoid processes. The falx cerebelli, sickle-shaped, separates 

 the cerebellar hemispheres. It is free anteriorly but attached 

 above to the tentorium and below to the occipital, bifurcating 

 to enclose the occipital sinuses. The diaphragma sellce covers 

 the pituitary fossa; the infundibulum pierces its centre. Be- 

 tween the dura and arachnoidea is the subdural space. [599] 



[25] 



