CH. XLVI.J 



THE CEREBRAL CORTEX. 



647 



Figure 479 represents a horizontal view through the hemi- 

 sphere. The internal capsule (c) at the point * makes a bend 

 called the genu or knee, behind which the motor-fibres, and more 

 posteriorly still the sensory-fibres, 

 pass. The connection between 

 cerebrum and cerebellum is also 

 indicated ; one cerebral hemisphere 

 is connected with the opposite cere- 

 bellar hemisphere by the superior 

 cerebellar peduncle which decus- 

 sates with its fellow in the mid- 

 brain. 



The remainder of the white 

 matter consists of association fibres 

 which run from convolution to 

 convolution. 



Histological Structure of the 

 Cerebral Cortex. 



The cortex consists of the follow- 

 ing five layers (Meynert) : 



i. Superficial layer with abun- 

 dance of neuroglia and a few small 

 multipolar nerve-cells. 2. A thin 

 layer of a large number of closely 

 packed small nerve-cells of pyra- 

 midal shape. 3. The most import- 

 ant layer, and the thickest of all : 

 it contains many large pyramidal 

 nerve-cells, each with a process run- 

 ning off from the apex vertically 

 towards the free surface, and 

 lateral processes at the base which 

 are always branched. There is also 

 a median process from the base 

 of each cell which becomes con- 

 tinuous with the axis-cylinder of 

 a nerve-fibre. The bundles of 

 fibres spread out in this layer. 



4. Numerous nerve-cells, some 



large and others small, forming the granular formation of Meynert. 



5. Spindle-shaped and branched nerve-cells of moderate size 

 arranged chiefly parallel to the free surface (fig. 480). This layer 



Fig. 480. The layers of the cortical 

 grey matter of the cerebrum. 



(Meynert.) 



