504 



THE NERVOUS SYSTEM. 



the fissure of Sylvius, and in the olfactory bulb this arrangement 

 does not exist. These layers are : 



1. Molecular Layer. This is the most superficial, and consists 

 of neuroglia, a few small ganglion-cells, and a network of non- 

 medullated and medullated nerve-fibers, the latter forming a 

 delicate white lamina absent in contact with the pia mater. 



-Molecular 

 layer. 



- -Layer of 

 small pyr- 

 amidal 

 cells. 



| ~ Layer of 



large pyr- 

 amidal 

 cells. 



. Medullary 

 substance. 



Brush-like 

 teloden- 

 dron. 



Main den-' 

 drite. 



Secondary 

 dendrite. 



Layer of 

 polymor- 

 phous Basal 

 cells. deudrite. 



FIG. 295. Schematic diagram of 

 the cerebral cortex, after Golgi and 

 Ramon y Cajal (Bohmand Davidoff). 



Neuraxis 

 with col 

 laterals. 



FIG. 296. Large pyramidal cell from 

 the human cerebral cortex ; chrome-silver 

 method ; x 150 (Bohm and Davidoff). 



The non-medtillated fibers have their origin principally in the 

 small pyramidal cells of the second layer, but also come from the 

 dendrites and axis-cylinder processes of the cells of the first layer. 

 The nerve-cells of this layer have two or. three axis-cylinder 

 processes arranged horizontally, which terminate by arborization 

 in this superficial layer. 



2. Small Pyramid-cell Layer. The cells of this layer are small 



