392 DISSECTION OF THE RABBIT. 



collectively as the hind-brain. The cavities of the vesicles 

 remain in communication with each other throughout life, 

 and are spoken of in the adult as the ventricles of the brain. 



1. Dissection of the Brain. 



a. The cerebral hemispheres. 



Lay the brain with its dorsal surface upward, and gently 

 press the hemispheres apart : note the position of the corpus 

 callosum. 



Then, with the back of a knife peel off the portion of the 

 right hemisphere lying above the corpus callosum. Keep the 

 brain wet with spirit. 



i. The corpus callosum is a broad horizontal band 

 of fibres connecting the two hemispheres. 



ii. The structure of the hemisphere. 



a. The outer layer or cortex is a superficial invest- 

 ment of grey matter, about an eighth of 

 an inch thick. 



/3. The central or medullary portion consists of 

 white matter, i.e. of medullated nerve-fibres. 

 The fibres of the corpus callosum spread out 

 into and are continuous with it. 



iii: The lateral ventricle, or cavity of the hemisphere. 



Cut through the corpus callosum on the right side, so as 

 to open the lateral ventricle beneath it. Lift up the corpus 

 callosum, and carefully cut it away, so as to expose the ven- 

 tricle fully, leaving a narrow strip along its inner edge. 



The lateral ventricle, opposite the middle 

 of .the hemisphere, is wide from side to side, 

 but shallow dorso-ventrally. Anteriorly, it 

 extends forwards as a narrow vertical slit, 

 the anterior cornu, which lies nearer the inner 

 than the outer surface of the hemisphere. 



Posteriorly, the lateral ventricle curves 



