846 



NEUROLOGY 



Nerve Fibers. These fill up a large part of the intervals between the cells, and may be medul- 

 lated or non-medullated the latter comprising the axons of the smallest pyramidal cells and 

 the cells of Golgi. In their direction the fibers may be either tangential or radial. The tangential 

 fibers run parallel to the surface of the hemisphere, intersecting the radial fibers at a right angle. 

 They constitute several strata, of which the following are the more important: (1) a stratvim 

 of white fibers covering the superficial aspect of the molecular layer (plexus of Exner) ; (2) the 

 band of Bechterew, in the outer part of the layer of small pyramidal cells; (3) the band of Gennari 



Molecular 

 layer 



Layer of 



small 



pyramidal 



cells 



Layer of 



large 



pyramidal 

 cells 



Layer of 



polymorphous 



cells 



"" Plexus of Exner 



~~ Band of Bechterew 



Outer 'band of Bail- 

 larger, or band of 

 Gennari 



- -- Vertical fibers , 



Internal band of 

 Baillarger 



Deep tangential 

 fibers 



White medullary 

 substance 



FIG. 754. Cerebral cortex. (Poirier.) To the left, the groups of cells; to the right, the systems of fibers. Quite 

 to the left of the figure a sensory nerve fiber is shown. 



or external band of Baillarger, running through the layer of large pyramidal cells; (4) the internal 

 band of Baillarger, between the layer of large pyramidal cells and the polymorphous layer; (5) 

 the deep tangential fibers, in the lower part of the polymorphous layer. The tangential fibers 

 consist of (a) the collaterals of the pyramidal and polymorphous cells and of the cells of Martinotti; 

 (6) the branching axons of Golgi's cells; (c) the collaterals and terminal arborizations of the 

 projection, commissural, or association fibers. The radial fibers. Some of these, viz., the axons 

 of the pyramidal and polymorphous cells, descend into the central white-matter, while others, 



