CEREBRUM 



181 



A. Cells (fig. 95 A). 1. Plexiform layer. At the surface of 

 the cortex is a thin layer of small irregular cells. 



2. Layer of small pyramidal cells. 



3. Layer of medium pyramidal cells. 



4. External layer of large pyramidal cells. 

 Some writers class layers 2, 3, and 4 as one. 



5. Layer of stellate cells. This 

 is a thin but well-defined layer 

 of minute polymorphic cells lying 

 rather more than halfway down 

 the thickness of the cortex. 



6. Internal layers of large 

 pyramidal cells. 



7. Layer of spindle-shaped cells. 



B. Fibres. The relationship of 

 the medullated fibres to these 

 layers is shown in fig. 95 .#). 



1. On the surface is a fibreless 

 layer. 



2. Under this is a thin layer 

 of more or less horizontal fibres, 

 the zonal layer. 



3. Under this is a thicker ir- 

 regular layer of fibres, the supra- 

 radiary layer. 



4. Next comes a band of fibres 

 often so well developed as to make 

 a white streak in the grey matter. 

 This is the line of Baillarger. In 

 the regions of the calcarine fissure 

 in apes and in man, when it is 

 specially marked, it is known as 

 the layer of Gennari. 



5. Radiary zone. A thick 

 layer of white fibres chiefly pass- 

 ing to and from the subjacent 

 white substance. 



It should be remembered that 

 the layer of stellate cells lie just 

 outside Baillarger's layer of fibres. 



FIG. 91. Diagrammatic Horizon- 

 tal Section through Base of Cere- 

 bral Hemisphere, showing (1 ) 

 the outgoing fibres for the leg, 

 arm, and face springing from the 

 cortex of the rolandic areas, pass- 

 ing through the internal capsule 

 between the thalamus and the 

 lenticular nucleus. The face 

 fibres cross in the pons, the leg 

 and arm fibres in tlie medulla. 

 (2) The incoming fibres (fillet, 

 eye) form their stations in the 

 thalamus, and then pass on to 

 the cortex 



