512 



THE NERVOUS SYSTEM 



the case in the more superficial layers. They are intermediate in 

 size, between the cells of the second and the third layers. The 

 neuraxes of the inner polymorphous cells, in large part, pass to 

 the white matter of the medulla, though some of them are dis- 

 tributed laterally to neighboring convolutions. Their dendrites 

 are partially distributed within the layer in which they arise, but 

 by far the larger portion pass to the more superficial pyramidal 

 cell layers. Many of the nerve cells of 



f ^ v --,_ this layer, e. g., the granule cells, are 



without a distinct rim of cytoplasm, and 

 are therefore cytochrome, according to 

 JSTissl. The larger forms stellate, pyram- 

 idal, and fusiform are parapyknomor- 

 phic arkyochrome cells. 



It is noticeable that, as a rule, the 

 dendritic processes from the cells of all 

 five layers are distributed either in the 

 same plane as their cell bodies, or they 

 pass toward the surface, where many of 

 them enter the superficial molecular layer. 

 The neuraxes, on the other hand, are di- 

 rected inward toward the white matter of 

 the cerebral medulla, in which they pass, 

 either as association or as projection 

 fibres, to many very distant parts. Nota- 

 ble exceptions to this latter rule, however, 

 are the so-called cells of Martinotti, which 

 occur to some extent in all layers, but 

 which, though found in the pyramidal 

 layers, are especially numerous among the 

 polymorphous and granule cells. They 

 are small polymorphous cells, which send 

 their neuraxes to the superficial molecular 

 layer, giving off collaterals on their way. 



The cell types in other portions of the 

 cortex correspond very closely to those 

 of the motor area. There are, however, 

 slight but characteristic variations which 

 are worthy of notice. 



THE CORTEX OF THE PARIETAL LOBE (also of the frontal, 

 temporal, convex surface of the occipital lobes, and the insula) 



FIG. 396. HUMAN CORTEX 

 CEREBRI, PARIETAL LOBE. 



a, tangential fibre layer; 

 6, outer polymorphous cells ; 

 c, small pyramidal cells ; d, 

 outer large pyramidal cells ; 

 e, granule cells ; /, inner large 

 pyramidal cells ; g, inner poly- 

 morphous cells ; ft, white mat- 

 ter of the medulla. Nissl's 

 stain. Moderately magnified. 

 (After Schlapp.) 



