2 THE MENINGES OF THE BRAIN. 



and falx cerebelli hang vertically in the longitudinal fissure of 

 the cerebrum and the posterior notch of the cerebellum; and,' 

 into the transverse fissure of the cerebrum, extends horizontally the 

 tentorium cerebelli. The falx cerebri (Figs, i, and 4) is attached 

 in front to the crista galli and behind to the internal occipital pro- 

 tuberance and superior surface of the tentorium; the falx cere- 

 belli (Fig. i) continues from the inferior surface of the tentorium, 

 along the occipital crest, to the posterior border of the foramen 

 magnum. The bony attachment of the tentorium cerebelli 

 (Fig. 2) is to the internal protuberance and the lateral arms of 

 the crucial ridge forward to the petrous bone; and, then, it is 

 along the superior border of the petrous bone to the clinoid proc- 

 esses -of the sphenoid. Between its clinoid attachments there is 

 a deep bay, the incisura tentorii, which transmits the midbrain. 

 The diaphragma sellae is a small centrally perforated sheet of 

 dura which covers the hypophyseal fossa. 



Sinuses. (Sinus dura matrix}. Large venous passages lined 

 with endothelial cells, and called sinuses, are situated between 

 the layers of the dura (Figs, i, 2, 3 and 4). In the convex and in 

 the free border of the falx cerebri are, respectively, the superior 

 sagittal sinus (s. sagittalis superior) and the inferior sagittal 

 sinus (s. sagittalis inferior). The superior (Fig. T) extends 

 from the foramen caecum back to the confluens sinuum (torcular 

 Herophili,) located at the internal occipital protuberance. Having 

 run through the posterior two-thirds of the concave border of 

 the falx cerebri, the inferior sagittal sinus joins the great cerebral 

 vein at the margin of the tentorium and forms the straight sinus 

 (s. rectus). The latter runs through the middle of the tentorium 

 to the confluens (Fig. 2). The occipital sinus (s. occipitalis) 

 traverses the falx cerebelli from the foramen magnum upward 

 to the same point. In the confluens sinuum the transverse 

 sinuses (s. transversi) rise (Fig. 2). Grooving the horizontal 

 arms of the crucial ridge, each runs outward in the tentorium to 

 the base of the petrous bone, where it receives the superior petrosal 

 sinus; it then turns downward through the sigmoid fossa, com- 

 municates with the occipital sinus and unites with the inferior 

 petrosal sinus in the jugular foramen. Situated on either side 



