THE BRAIN AND SPINAL COED. 



207 



nearly the whole of the cerebrum of fishes, amphibians, reptiles, 

 and birds. 



(2) The Corpus Striatum. 



(3) The Neo-pallium. This comprises the remainder of the 

 cerebral vesicle. With the evolution of the higher mammals the 

 neo-pallium became bigger and bigger until in man it constitutes 

 by far the greater part of the cerebrum. "With its development 

 the corpus striatum also became increased, while the rhinen- 

 cephalon became more and more reduced. 



The Velum Interpositum. — We have seen that the roof plate 



ant. horn 



olfact depression 

 .for. of Monro 



caud. nucleus 

 choroid plexus, 

 choroidal fissure 

 uelum interposit 



desc. horn 



roof of 3rd vent 

 optic thalamus 

 thalamen cephalon 



inflect, of 

 mes. wall. 



mid brain 



Fir 170 —A dorsal view of the Fore and Mid-brain at the 5th week of development 

 'to show the formation of the Velum Interpositum. The Cerebral Vesicles are 

 laid open and the inflection of their mesial walls shown on the ingrowing Velum. 

 The Roof Plate of the 3rd Ventricle is also exposed. (Modified from His.) 



of the 4th ventricle (hind-brain) forms the cerebellum in front, 

 while its posterior half becomes the inferior medullary velum— a 



