PART X. 



OF THE BRAIN AND SPINAL MARROW : OF THE EYE AND 



THE EAR. 



CHAPTER XII. 



OF THE BRAIN. 



THE whole of the soft mass, which fills the cavity of the 

 cranium, is called the brain. This mass is covered by three 

 membranes : two of which were called meninges or matres, by 

 the ancient anatomists : who believed that all the other mem- 

 branes of the body originated from them. 



These membranes are denominated the Dura Mater, Tunica 

 Arachnoidea, and Pia Mater. 



Of the Membranes of the Brain, and Sinuses of the Dura 



Mater. 



Dura Mater. 



The Dura Mater encloses the brain and all its appendages, 

 and lines the different parts of the cranium. It consists of one 

 membrane of a very dense texture, which in several places is 

 composed of two or more lamina. It is the thickest and strong- 

 est membrane of the body, and is composed of tendinous fibres, 

 which have a shining appearance, particularly on its inner sur- 

 face. In many parts these fibres run in a variety of directions, 

 and decussate each other at different angles. 



The dura mater adheres every where to the surface of the 

 cranium, in the same manner as the periosteum adheres to the 



