THE BRAIN. 385 



verse commissures connecting the two halves of the brain 

 with each other. 



Remove the hardened brain from spirit and examine it in 

 a small dish of water or weak spirit. 



A. The Brain-membranes. 



1. The dura mater is the tough connective-tissue membrane 



which lines the cranial cavity. The greater part of 

 this membrane is left in the skull on removal of the 

 brain. It projects into the cranial cavity as a 

 median vertical fold, the falx cerebri, which lies 

 between the hemispheres ; and a transverse fold, 

 the tentorium, which separates the hemispheres* 

 from the cerebellum. 



2. The pia mater is a much thinner and very vascular 



layer of connective tissue, which closely invests the 

 brain. The blood-vessels running to and from the 

 brain he in it. 



B. External Characters of the Brain. 



Strip off the pia mater from the brain with fine forceps as 

 completely as possible, taking great care on the base of the brain 

 not to drag away the nerve-roots. 



1. The dorsal surface of the brain. 



a. The cerebral hemispheres, which form the anterior 

 two-thirds of the brain, are a pair of broad 

 triangular bodies, pointed in front and closely 

 apposed to each other along the median plane. 



Their surfaces are smooth and convex : they 

 are marked by a few shallow grooves, or sulci ; 

 and are divided by rather more conspicuous 

 grooves at their outer edges into anterior or 

 frontal, and posterior or parietal lobes. 



The two hemispheres are connected with 

 each other by a large transverse commissure, 

 the corpus callosum, which is asily seen on 



