FEOG 247 



ity, viz., the fourth cerebral ventricle, immediately 

 below the pia. Is the choroid plexus thicker than 

 other parts of the membrane ? Is it more vascu- 

 lar ? Lining the wall of the neural canal look for 

 another membrane, the dura mater. Is it col- 

 ored hke the pia ? Is it as thin and vascular as 

 the latter? 



II. The central nervous system, 

 a. The brain. — Examine its dorsal surface. "What 

 is its general shape ? Is it bilaterally symmetri- 

 cal ? Is its surface smooth, or marked with ridges 

 and furrows, i. e., convoluted ? "What is its po- 

 sition with reference to the eyes ? Lying between 

 the latter organs find on the brain two elongated 

 masses, the cerebral hemispheres, at the an- 

 terior end of each of which is an olfactory 

 lobe, from which proceeds forward a nerve, the 

 olfactory nerve. What is the shape of the ce- 

 rebral hemispheres ? "Why are they called " hemi- 

 spheres " ? How long are they ? How wide ? Are 

 they connected ? If so, how ? How much of the 

 brain do they form ? Are the olfactory lobes 

 sharply separated from the cerebral hemispheres ? 

 Are the lobes connected with each other? "What 

 is their shape? How do they compare in size 

 with the hemispheres ? Immediately behind the 

 hemispheres find a diamond-shaped area, the tha- 

 lamencephalon. Note that the pia mater here 

 forms another choroid plexus. Near the middle 

 of the roof of the thalamencephalon find the re- 

 mains of the stalk of the piaeal gland, the gland 

 probably having been torn away when the skull 

 was removed. Cut away the choroid plexus and 



