354 DISSECTION OF THE BABBIT 



optic lobes to the cerebellum, and forming the 

 roof of the anterior half of the fourth ven- 

 tricle. 



iii. The velum medullae posterius is a thin mem- 

 brane, forming the roof of the posterior half 

 of the fourth ventricle. 



iv. The cerebellum is attached to the dorsal surface, 

 at the junction of the vela medullse anterius 

 and posterius. It consists of an outer layer 

 of grey matter, which is very deeply folded, 

 and a central much-branched mass of white 

 matter, the section having a tree-like appear- 

 ance, which has given rise to the name arbor 

 vitae. 



v. The pons Varolii is seen, in transverse section, 

 crossing the ventral surface of the anterior 

 part of the hind-brain, opposite the velum 

 medullae anterius. 



3. Transverse sections of the brain, 



If another brain can be obtained, it should be cut with a 

 razor into a series of transverse sections, about an eighth of 

 an inch thick, and the sections arranged in order in a dish of 

 spirit. 



Such a series of sections affords very instructive 

 views of the mutual relations of the several parts of 

 the brain. 



