394 DUKA MATER OF THE BRAIN. 



cranium, which are continued into the periosteum, and 

 through the optic foramen around the optic nerve, into 

 the sclerotica of the eye. At some points the attachment 

 to the hones is much more feeble than at others, as in 

 the occipital fossse, and upon the squamous and parietal 

 bones. 



The strength of this connection varies at different peri- 

 ods of life. In the young it is so strong as to require the 

 scissors, and considerable force, to effect a separation. In 

 the adult the attachment is more easily broken ; while in 

 old age it becomes so strong again as to tear in shreds in 

 the attempt at separation. 



When the cranium has been successfully removed, its 

 external surface, besides its roughness, also presents nu- 

 merous red dots, which is owing to the rupture of vessels 

 that form a part of the bond of union. 



On the vertex, the dura mater has a cribriform appear- 

 ance, having little, granular, pale bodies projecting from 

 it, called glandulce Pacchioni, which we will notice again 

 presently. Kaise the dura mater by making an incision 

 through it on either side of the middle line; its internal 

 surface is found to be smooth, polished, and lubricated 

 with serum. 



Its structure is fibro-serous. The fibrous layer, forming 

 a very strong and firm capsule for the brain, consists of 

 two lamina, the outer acting as the periosteum, the inner 

 going to form the different reflections of the brain. Its 

 serous layer is the reflected or parietal portion of the 

 arachnoid, strongly adhering to the dura mater, and al- 

 ways in contact with the surface of the brain. 



Blood-vessels, (Fig. 8.) The arteries supplying the dura 

 mater come from the ophthalmic and internal carotid, which 

 send branches to its anterior portion. Its lateral parts are 

 supplied by the middle meningeal artery, a branch of the in- 

 ternal maxillary, its posterior portion by the occipital and 

 vertebral, and its basilar by the pharyngeal, vertebral and 

 internal carotid. Its veins enter the sinuses, except those 

 of the middle artery, which are vena? comites. 



