STRUCTURE OF THE CEREBRAL CORTEX 



203 



between the two layers of the 

 grey matter is an incomplete 

 stratum of large flask- shaped 

 cells (cells of Purkinje, c). 

 Each of these gives off from its 

 base a fine process, which be- 

 comes the axis-cylinder of one 

 of the medullated fibres of the 

 white centre, while from the 

 opposite pole of the cell large 

 ramified processes spread out 

 into the superficial layer of 

 the grey matter, and some of 

 these processes become con- 

 nected with its small nerve- 

 cells (fig. 238). 



~ Structure of the cerebrum. 

 The grey matter of the ce- 

 rebral cortex is described as 

 being composed of a number 

 of layers, but they are not 

 sharply marked off from one 

 another. The following are 

 usually distinguished (fig. 

 239). 



1. Most externally a thin 

 stratum containing a few scat- 

 tered cells, probably neuro- 

 glia-cells. In the most super- 

 ficial part of this layer imme- 

 diately under the pia mater, 

 is a very thin stratum of 

 medullated nerve-fibres. 



2. A layer of closely set 

 small pyramidal nerve-cells 

 several deep. This layer is 

 also thin. 



3. A thick layer contain- 

 ing larger and longer pyra- 

 midal cells less closely set. 

 These cells are largest in the 

 deepest part of the layer ; and 

 in the region of the motor 

 centres of the brain some of 

 them are of very large size, 

 and are collected into small 

 groups. 





