312 



NORMAL HISTOLOGY. 



FIG. 341. 







.. 







by the cells are so plentiful and 

 closely interwoven that they con- 

 stitute no inconsiderable part of 

 the fine ground reticulum of this 

 layer. Immediately beneath the 

 surface of the nervous matter, the 

 sub-pial zone forms a narrow 

 stratum (10-25 /*) composed al- 

 most entirely of neuroglia, in 

 which lie numbers of spider or 

 Deiters's cells. The nerve-fibres 

 of this layer extend parallel with 

 the free surface. 



2. The second layer (.25 

 mm.) is characterized by the 

 profusion of its closely- packed 

 small triangular or pyramidal 

 nerve- cells, the branched pro- 

 toplasmic processes of which 

 extend in various directions to- 

 wards the periphery, while their 

 axis-cylinder processes termi- 

 nate within the gray matter, often 

 ending in T-branches which are 

 directed almost at right angles to 

 the main process. 



3. The third layer, the for- 

 mation of the cornu Ammonis, 

 is the thickest stratum of the 

 cerebral cortex, reaching in places 

 a breadth of i mm., and contains 

 the most characteristic nervous 

 elements of the cerebrum, the 

 large pyramidal ganglion- 

 cells. This layer is not sharply 

 defined from the preceding, since 

 the small cells of the latter are grad- 

 ually replaced by the larger pyram- 



Section of human cerebral cortex stained with 

 sodium carminate : A , outer layer, poor in nerve- 

 cells, rich in neuroglia ; B, layer of numerous 

 small nerve-cells ; C, layer of large pyramidal gan- 

 glion-cells ; D, layer of irregular numerous but 

 small nerve-elements ; /, pial tissue ; v, v 1 ', blood- 

 vessels. 



