360 D. DAVIDSON BLACK 



and usually centrally placed, and shows as a rule a well developed eosino- 

 phile karyosome. In the cytoplasm Nissl bodies are present, but show 

 as distinct and sharply defined granules only in some cases ; in others the 

 tigroid substance is very variable in its appearance. In all cases there 

 is a well defined circumnuclear zone practically free from Nissl substance. 

 In a few cases the nucleus is eccentric and irregular in shape. 



In Weigert stained sections of these areas, the following dis- 

 tribution of medullated tissue was noted: Area 5, many medul- 

 lated fibers in both zonal layer and medulla, no radial fibers; 

 Area 4, a few medullated fibers in the zonal layer and numerous 

 medullated fibers in the medullary center; Area 3, occasional 

 medullated fibers in the zonal layer and a few present in the 

 medulla; Area 2, no medullated fibers in the zonal layer and a 

 very few in the medullary center; Area 1, no medullated fibers 

 anywhere. 



DISCUSSION 



Cortical lamination 



The cell lamination in this case shows a number of points of 

 resembance to that obtaining in the normal cortex. Thus, there 

 is everywhere to be distinguished a zonal or outer fiber lamina 

 and the cortex in all those regions not subject to marked modi- 

 fication by the entering thalamic fibers may be divided into an 

 outer and an inner cell stratum by the lamina described as Layer 

 III This division, then, would correspond to that obtaining 

 in the normal cortex where, as Bolton and Moyes (3) have shown, 

 there is a very early splitting of the primary cortex into two 

 layers by the formation of an inner fiber lamina. 



However, the lamination also shows several quite distinctive 

 features not at all comparable to the normal. The stratum 



Fig. 8^ Section through cortex of posterior pole of the right posterior lobe. 

 Area 4, region indicated in figure 2. X 65. 



Fig. 9. Section through the cortex at the region of junction of the thalamus 

 and cerebrum. Area 5, position indicated in figure 3. X 65. 



^ In figures 8 and: 9, certain cortical layers, which are described in figures 4 to 7, 

 are not represented or numbered. It is not the intention, however, to imply that 

 the laminae bearing the same numbers throughout these figures are necessarily 

 altogether homologous. This point is made clear in the text. 



