1200 



HUMAN ANATOMY. 



of the petrous portion of the temporal bone, and thence to the posterior clinoid pro- 

 cess. From the internal occipital protuberance as far as the parietal bone, this line of 

 attachment corresponds with the course of the enclosed lateral sinus (page 867) ; but 

 beyond, the venous channel leaves the tentorium in its descent to the jugular fora- 

 men, the farther attachment of the tentorium enclosing the superior petrosal simis. 

 Since the anterior border of the tentorium springs, on each side, from the anterior 

 clinoid process, it follows that the two margins of the crescentic septum intersect in 

 advance of the apex of the petrous bone, the posterior border turning inward to the 

 posterior clinoid process, whilst the anterior margin is connected with the anterior 

 process. The free tentorial border, in conjunction with the dorsum sellae, defines an 

 arched opening, the incisura tentorii, through which the mesencephalic portion of 

 the brain-stem is continued into the cerebral hemispheres, the highest point of this 

 aperture lying just behind the splenium of the corpus callosum. 



FIG. 1034. 



-Skin 



Superior longitudinal sinus 



Falx cerebri 



Cerebral 

 hemisphere 



Posterior horn of 

 lateral ventricle 



Tentorium 

 Left lateral sinus 



Fibro-aponeurotic layers of scalp 



Parietal layer of dura 



Bone 



Inferior longitudi- 

 nal sinus, cut 

 obliquely 



Posterior horn of 

 lateral ventricle 



entorium 

 'Right lateral sinus 



erebellum 



Superior worm 



N^ Inferior worm 



Occipital sinus 



Frontal section of head, viewed from behind, showing relations of dura mater to cerebral hemispheres and 



cerebellum and position of sinuses. 



The falx cerebelli is a small sickel-shaped dural fold which descends in the 

 mid-line from the under surface of the tentorium, with which its broader upper end 

 is attached, towards the foramen magnum. In the vicinity of this opening its apex 

 bifurcates into smaller folds that fade away on either side of the foramen. Its poste- 

 rir border, attached to the vertical internal occipital crest, contains the small occipital 

 sitiHSt-s, or sinus when these channels are fused. The narrow crescent projects into 

 tin- posterior cerebellar notch and thus intervenes between the hemispheres of th 

 cerebellum. 



The diaphragma sellae is an oval septum of dura, which roofs in the pituitary 



and is continuous on either side with the visceral or inner layer of the wall of 

 the cavernous sinus. The diaphragm contains a small aperture, the forawcn dia- 

 phragwatix, through which the infundibulum connects the enclosed pituitary body 

 with the brain. 



The structure of the dura presents the histological features of dense fibro- 

 elastic tissue, in which the elastic constituents, however, are greatly Overshadowed 

 by the white fibrous bundles. The inner surface of the dura is covered with endo- 



