THE SENSOEY AREA 



617 



rected inward toward the white matter of the cerebral medulla, in 

 which they pass, either as association or as projection fibers, to many 

 very distant parts. Notable 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 pyram- 

 idal layers, are especially numerous among 

 the polymorphous and granule cells. They are 

 small polymorphic cells, which send their axons 

 to the superficial molecular layer, giving off 

 collaterals on their way. 



The cell types in other portions of the cor- 

 tex 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] sensory area 

 presents a seven layer type, the additional 

 layers resulting from an aggregation of the 

 granule cells into one plane, which thus di- 

 vides the large pyramidal cell layer. This 

 type, therefore, presents the following layers : 



1. Molecular or tangential fiber layer. 



2. Outer polymorphous cell layer. 



3. Small pyramidal cell layer. 



4. Outer large pyramidal cell layer. 



5. Granule cell layer. 



6. Inner large pyramidal cell layer. 



7. Inner polymorphous cell layer. 



The distribution of this cortical type is 

 suggestive of a close relation to the great asso- 

 ciation centers. Moreover, its most noticeable 

 characteristics are the abundance of its granule 

 cells and the relative paucity of pyramidal cells, 

 especially those of the giant pyknomorphic 

 variety. 



In the visual area median surface of the occipital lobe the for- 

 mation is described as either a six or an eight layer type. The pyram- 

 idal cell layers are reduced to extreme thinness, the giant pyramids 

 39 



FIG. 533. HUMAN COR- 

 TEX CEREBRI, PARIE- 

 TAL LOBE. 



a, tangential fiber layer; 

 6, outer polymorphous 

 cells; c, small pyramidal 

 cells; d, outer large pyr- 

 amidal cells; e, granule 

 cells;/, inner large pyram- 

 idal cells; g, inner poly- 

 morphous cells; h, white 

 matter of the medulla. 

 Nissl's stain. Moderately 

 magnified. (AfterSchlapp.) 



