THE VISUAL AREA 



513 



presents a seven layer type, the additional layers resulting from 

 an aggregation of the granule cells into one plane, which thus 

 divides the large pyramidal cell layer. This type, therefore, pre- 

 sents the following layers : 



1. Molecular or tangential fibre 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 association 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 me- 

 dian surface of the occipital lobe 

 the formation is described as either 

 a six or an eight layer type. The 

 pyramidal cell layers are reduced to 

 extreme thinness, the giant pyra- 

 mids being noticeably deficient. 

 The stripes of Baillarger, thin layers 

 of tangential fibres on the deeper 

 portions of the cortex, are especially 

 distinct. So many granule cells are 

 scattered among those of the pyram- 

 idal type that it becomes scarcely 

 possible to distinguish from one an- 

 other the second, third, and fourth 

 layers. When these three layers 

 are individually considered, the type 

 presents eight layers; if, on the 

 other hand, they are collectively 

 considered as a single stratum, 

 the type presents but six layers. 



With this reservation, the following layers may be distin- 

 guished : 



34 



M ' 



I'T 



,Vs '* V. 



'<* '* ,.* . 



.?:'>:::: 



\ _iii.- v ..: 



FIG. 397. HUMAN COKTKX CEREBBI, 

 OLFACTORY REGION". 



o, tangential fibre layer ; 6, white 

 matter of the medulla. Nissl's 

 stain. Moderately magnified. (After 

 Schlapp.) 



