INTEBNAL FEATDEBS OP THE HUMAN BEAIN 



397 



by four little bodies called the corpora quadrigemina. Its 

 floor is the mediilla and the pons Varolii. 



The fourth ventricle projects upward toward the 

 cerebellum, and the internal structure of this organ shows 

 a branching, treelike core of white matter (the arbor 

 vitoe) surrounded on the outside by gray matter. The 

 lobes of the cerebellum are only partly separated, the 

 fissure dividing them being very shallow. The floor and 

 sides of the fourth ventricle are formed by the medulla, 

 and this cavity is continued backward as the neural 

 cavity of the spinal cord. 



From the above description it will be seen that the 



Corpus Striatum 

 -Fornix 



-Optic Thalamus 

 -Pineal Body 



I orpora Quadrigemina 



* rochlear Nerve 



Fig. 185 — Section of brain at right angles to longitudinal fissure. 



brain is actually a hollow organ with a continuous 

 cavity surrounded by various outgrowths or walls and 



