THE MOTOK AREA 



615 



M.P. 



Subm.P. 



Gt.P.P. 



THE MOTOR AREA 



In the motor area, including the pre-Eolandic or pre-central gyrus 

 and a posterior portion of the frontal lobe, the cortical cells form five 

 tangential layers, as follows: 



1. Molecular layer. 



2. Outer polymorphous cell layer. 



3. Small pyramidal cell layer. 



4. Large pyramidal cell layer. 



5. Inner polymorphous cell layer. 

 The MOLECULAR LAYER (stratum 



zonale) consists of a net work of fine 

 dendronic fibers, derived from the deeper 

 layers, which are disposed in tangential 

 meshes beneath the pia mater. Occa- 

 sionally small cells, apparently displaced 

 from the deeper cell layers, are scat- 

 tered among these fibers; they are of 

 polymorphous form, and their processes 

 are confined to the molecular layer. The 

 surface of the molecular layer is cov- 

 ered by a marginal velum of neuroglia 

 homologous with that beneath the pia 

 mater of the spinal cord. 



The SECOND, or OUTER POLYMOR- 

 PHOUS, CELL LAYER, is a thin stratum. 

 Its cells are frequently clumped, thus 

 forming groups of various size. This 

 grouping is, however, more distinct in 

 some other regions, e.g., the olfactory 

 area, than in the motor area itself. 



The THIRD LAYER, SMALL PYRAMIDAL 



CELLS, is somewhat thicker than the 



above. It consists of numerous small 



cells triangular, pyramidal, or pyri- 



form in shape whose pointed apices are 



directed toward the surface. Three sets 



of dendrons are given off by these cells, an apical process which passes 



outward to ramify in the outer molecular layer, and from either side 



PolP. 



FIG. 531. DISPOSITION OF THE 

 NERVE FIBERS IN THE CERE- 

 BRAL CORTEX OF MAN. 



Between the vertical bands of 

 radial fibers are the areas of inter- 

 radial feltwork. The supraradial 

 Jeltwork includes the tangential 

 fiber layer or stratum zonale (M. 

 P.), and the stripe of Bechterew 

 (Subm.P.}. c.z., subpial neurogliar 

 layer; Gt.P.P., outer stripe of Bail- 

 larger; Pol.P., inner stripe of Bail- 

 larger; W., white matter. (From 

 Barker, after L. Andriezen.) 



