THE CORTICAL GRAY MATTER. IQI 



cells (Bevin Lewis), are "pyraform" in shape. They are loaded 

 with Nissl bodies and give off one axone and many dendrites. The 

 lateral and basal dendrites ramify in the radiary zone; the dendrite 

 of the summit runs straight out toward the surface and like the 

 same process from other pyramids, arborizes in the stratum zonale 

 of the plexiform layer; the axone enters the medullary substance 

 and becomes a projection, association or commissural fiber. 

 The giant pyramids characterize the motor cortex. No where 

 else are they so large. Neither do they have in any other region 

 the " pyraform" shape or the definite nest-like grouping seen in 

 the anterior central gyrus. They measure twenty-five by sixty 

 microns in the leg area of that gyrus ; twenty by forty- five microns 

 in the arm area; and, in the head area, seventeen by thirty-five 

 microns (Bevin Lewis). In cases of amyotrophic lateral sclerosis 

 studied by Campbell, 87.5 per cent, of these cells in the affected 

 area were entirely destroyed and those remaining showed signs 

 of degeneration. Both the internal and external large pyramids 

 were thus affected in the anterior central gyrus, so they are motor 

 in that gyrus; but they were not degenerated in any other part 

 of the cortex. 



7. The fusiform layer (Figs. 58, 59, 60 and 61) is found 

 every where in the cerebral cortex. It presents very little topo- 

 graphical variation. Its spindle-shaped cell-bodies lie in the 

 deep part of the radiary zone and in the felt-work of Kaes. The 

 long axes of the spindles are perpendicular to the surface in the 

 crown of a gyrus but are parallel with it in the fissural walls and 

 floor. From these cell-bodies one axone and several dendrites 

 are given off. The function of the spindle cell is probably asso- 

 ciation. The felt-work of Kaes is a rich plexus of fibers in which 

 the white and gray substance meet. It is produced by the inter- 

 mingling of the association, commissural and projection fibers. 

 Scattered here and there through all the layers of the cortex are 

 two atypical neurones, viz., the dendraxones of Golgi, which arbor- 

 ize very richly and are associative in function; and, second, the 

 inverted pyramids of Martinotti. Of the latter the dendrites 

 terminate near the cell-body; but the axone runs out to the first 

 layer and, branching T-like, ramifies in the stratum zonale. 



