NERVOUS SYSTEM 



LXIII. — Dissection of Sheep's Brain. 



Apparatus. — Sheep's head, bone forceps, hammer, scalpel, needle, 

 forceps, 50% alcohol. 



Directions. — A. To Remove Brain from SkulL Strike 

 the top of the skull with the hammer so as to crack the 

 bone, but not to force it into* the brain ; and then carefully 

 remove the pieces with the bone forceps. Be careful not 

 to injure the underlying membrane (dura mater) which 

 lines the skull and covers the brain. After the top of the 

 skull is removed slit this dura mater around the edge, and 

 remove it, exposing the brain. Note that over the surface 

 of the brain is another membrane, the pia mater. Now 

 carefully lift the brain from the floor of the skull, beginning 

 at the front. Notice that it is bound by nerves and portions 

 of the dura mater. Cut these nerves, leaving as long ends 

 as possible, and do not cut off the olfactory lobes which are 

 on the under side of the brain. Place the brain in 50% 

 alcohol to harden, for several days.^ 



J5. The Coverings of the Brain. Tear off a little of the 

 dura mater with the forceps. Does it tear easily? Are 

 both sides of it smooth? Where are its blood vessels? 

 What do they feed? 



Pick up a little of the pia mater (brain cover) with the 



1 Preserve the skull, with eyes, for use in Ex. LXX. 



97 



