530 



NAOKI SUGITA 



only a few cells, probably of the lam. mult., are to be seen (indus- 

 ium). Next to this, comes the area GG'-HH' , GG' marking the 

 mesial tip of the cortex, and HH' the knee of the cortical 

 cm-vature. This area has all the layers at HH', but all except 

 the lam. mult, disappear at GG'. 



k: f 



\ s I 



Fig. 4 Diagram of the frontal section, from the albino rat brain weighing 1.5 

 grams, at about 30 days in age, showing the cell-lamination of the cortex and the 

 localities at which the thickness of the cortex was measured, ss', plane in which 

 the sagittal section was taken; hh', level from which the horizontal section was 

 taken. Lines GG' , HH', KK', LL', MM', NN' and 00' indicate the borders of the 

 areas showing different types of cell-lamination. TV' fissura rhinalis. Between 

 M and N the claustrum — (CO— is seen. Gr.? marks the unidentified cell group 

 between AW and 00'. 



In the area HH'-KK', the radiation of the cells is perpendicu- 

 lar to the curved surface of the cortex, and the lam. mult, is 

 formed of a single layer. This area is here noted, because the 

 locality VI is in the middle of it and the line VI~VI' passes 

 through the tip of the curvature. 



The area KK'-LL' corresponds to the part, from which the 

 sagittal sections were cut, and shows distinctly the five layers. 

 In this area the lam. mult, is divided by a pale band into two 



