354 D. DAVIDSON BLACK 



DESCRIPTION OF CORTICAL AREAS 



Over the major portion of thecortex the cellular elements are 

 arranged in such a way as to form five quite definite strata. These 

 are: I, an outer or plexiform layer well marked over all areas; 

 II, an irregularly arranged cell layer; III, a layer sparsely supplied 

 with cells and which I have compared elsewhere with Bolton and 

 Moyes' (3) inner fiber lamina; IV, a layer of closely packed cells; 

 and V, a very thick inner or polymorphic cell layer. In many 

 regions this last layer tends to be subdivided into two strata 

 described when present as layers V and VI. 



After this general statement as to cell lamination, a more de- 

 tailed description of certain definite areas will be given. The 

 regions selected are as follows: (1) two different areas from the 

 anterior median lobe; (2) an area bordering on the right anterior 

 limb of the Y-shaped median furrow; (3) from the central portion 

 of the base of the left posterior lobe; (4) from the posterior pole 

 of the right posterior lobe; and (5) from the region of junction 

 of the thalamus and cerebral vesicle. 



Area 1 A. Cortex over the anterior basal portion of the ante- 

 rior lobe. Average thickness 6.7 or 6.8 mm. (fig. 4). 



Layer I. The zonal layer is thick, prominent and sharply marked off 

 from the subjacent stratum. Occasionally there are found in the deeper 

 parts of this layer irregular medium sized multipolar cells, but most of 

 the cells found here are of embryonic character. 



Layer II. A very irregularly arranged layer of cells showing but little 

 differentiation. The elements tend to be arranged in compact more or 

 less distinct groups. Not quite so thick as Layer I. 



Layer III. A layer poor in cellular elements and of inconstant thick- 

 ness owing to the varying depth of the superadjacent lamina. The line 

 of demarcation between this layer and the subjacent stratum is fairly 

 sharp. 



Layer IV. A very thick and well marked stratum of closely packed 

 cells. In the deeper portions of this layer there is some evidence of slight 

 cellular differentiation. The majority of the small cells show a tendency 



Fig. 4 Section through the cortex of the anterior basal portion of the anterior 

 lobe. Area 1 A; this region is indicated in figures 1 and 3. X 65. 



Fig. 5 Section through the cortex over the inner pillar of the anterior recurved 

 margin of the anterior lobe. Area 1 B, region indicated in figure 3. X65. 



