Turner, Morphology of the Avimt Brain. 267 



2. Originally this was a uniform layer parallel to the 

 surface of the epencephalon. 



3. Its present shape is due to a tendency to remain parallel 

 to the surface which has now become greatly increased by 

 convolutions. 



Although the cerebellar cortex is here described as being 

 composed of three distinct layers, it must be borne in mind 

 that neither membranes nor ventricles separate these lamina". 

 Nor is there either membrane or ventricle between the cortex 

 and the remainder of the epencephalon. 



White Substance of the Epencephalon . — The body or core 

 of the epencephalon is an irregular solid polyhedron, from 

 the periphery of which projections extend into all the irregu- 

 larities of the ental surface of the cerebellar cortex, and com- 

 pletely fill them. The centre of this core is occupied by a 

 small ventricle, which is connected with the fourth ventricle 

 by a narrow median isthmus. Histologically, this region is 

 composed almost exclusively of fibres. It contains, however, 

 two niduli, one of which is near the ventricle, while the other 

 is in the peduncle. 



Dentate Niduhis. — The nidulus near the ventricle is large 

 and conspicuous, and is known as the dentate nidulus. It 

 lies, for the most part, cephalad of the ventricle, and is very 

 irregular in outline. In many cases the nerve cells consti- 

 tuting this nidulus are large pyramidal cells, in other cases 

 they are multipolar, while in still others both pyramidal and 

 multipolar cells are found in the same nidulus. In some brains 

 these cells are densely compacted, while in others they are 

 only loosely aggregated. In all cases they lie in a bed 

 of nerve fibres. In my preparations these cells are so 

 densely stained that their nuclei and their nucleoli are 

 invisible. This nidulus is abundantly supplied with Deiter's 

 corpuscles. 



