CORTICAL CELL LAMINATION OF PAPIO HAMADRYAS. 629 



extended and pnssing gradually into the white matter through 

 isolated, scattered spindle-cells." 



Extent of Frontal and Prefrontal Types. — The 

 extent and boundaries of the frontal and prefrontal types are 

 shown in the figures, and hardly call for verbal description. 

 The limits are in most places vague and indefinite, but an 

 exception to this statement must be made in the case of the 

 sulcus arcuatus, which forms the posterior, and, to a certain 

 extent the upper boundary of the frontal area on the lateral 

 surface. On the nuterior wall of that fissure the cortex is 

 intermediate in character between the frontal and anterior 

 precentral types. 



The granule layer is slightly less accentuated than in the 

 former, while a few very well developed pyramidal cells, lying 

 some above it and some below it, are distinctly suggestive of 

 the latter type. This intermediate strip corresponds to 

 Brodmann's type 8. A difference will be noted in the region 

 between Papio and Cercopithecus, namely, thnt in the latter 

 the anterior precentral cortex extends in front of the sulcus 

 arcuatus and the intermediate type 8 lies well in the surface; 

 in the former the anterior precentral type stops at the bottom 

 of the fissure. 



The whole of the frontal lolje in the chimpanzee and the 

 orang lying in front of the intermediate precentral and 

 limbic areas is covered by the frontal and prefrontal types 

 of cortex. These agree in the possession of a distinct layer 

 of granules, wliich is broad and well-defined, but not so 

 densely crowded with cells as the corresponding stratum of 

 the parietal or temporal areas. Above and below there is in 

 eacli case a layer of large pyramids. The chief point of 

 difference lies in the smaller size, slenderer forms, and 

 reduced numbers of the constituent elements of these two 

 layei-s in the prefrontal area. There is no well-marked line 

 of demarcation, but the large pyramids, which are best 

 developed near the posterior border of the frontal area, 

 gradually undergo reduction in size and number. 



Brodmann's description of the corresponding region in the 



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