102 



HEAD AND NECK 



that the inner supporting layer may form strong partitions, 

 which pass in between certain parts of the brain ; and by 

 those partitions the cranial cavity is divided into compart- 

 ments communicating freely with one another, and each hold- 

 ing a definite subdivision of the brain (Figs. 33, 34). 



Frontal air sinus 



!ut edge of superior 

 sagittal sin 



Cerebral vein 



Arachnoid 

 >vermg cerebral 

 vein 



Cerebral ve 



Dura mater 



Anterior branch of 

 mid. meningeal arte 

 and accompanying 

 in 



rachnoideal 

 granulation 



Posterior bran 

 f mid. mening 

 rtery, with ve: 



ningof asuperi 

 cerebral vein 



FIG. 32. Superior Sagittal Sinus; Dura Mater; Middle Meningeal Artery 

 and Vein ; Arachnoidea and Superior Cerebral Veins. 



Dissection. -The points mentioned must now be verified. 

 Begin by tilting the head forwards. Support it in that position, 

 and make two incisions through the dura mater in an antero- 

 posterior direction one on each side of the superior sagittal 

 sinus, and along its whole length. From the mid-point of each 

 of the two incisions another cut must be made through the 

 corresponding lateral portion of the dura mater downwards to 

 the cut margin of the skull immediately above the ear (Fig. 32). 

 The dura mater covering the upper aspect of the brain will then 

 be divided into a central strip containing the superior sagittal 



