GROWTH OF THE CEREBRAL CORTEX ill 
9. The polymorphous cells in the ectal sublayer of the lamina 
multiformis are slightly larger than the pyamids of the same age. 
The polymorphous cells in the ental sublayer of the lamina multi- 
formis are somewhat larger than those of the ectal sublayer, 
but are irregular in shape and rich in cytoplasm. 
10. Two kinds of the neuroglia nuclei are found in the cortex. 
One staining deep blue with the carbol-thionine, smaller in size 
(2 to 5 micra in diameter on the slide) and having a radiating 
structure of the chromatin, and the other staining paler, swollen 
(‘blasig’) and somewhat larger in size (3 to 6 micra in diameter 
on the slide). 
11. Taking a general view of the ddta already presented in 
this series of studies, it is very interesting to note that the thick- 
ness of the cortex, the total number of the cortical nerve cells, 
and the size of the cortical cells all attain nearly their full 
values at the same age of twenty days (1.15 grams in brain 
weight); that is, at the weaning time of the albino rat. 
PAR sii 
ON THE INCREASE IN SIZE OF SOME NERVE CELLS IN THE CEREBRAL 
CORTEX OF THE NORWAY RAT (MUS NORVEGICUS) COMPARED 
WITH THE CORRESPONDING CHANGES IN THE ALBINO RAT 
To compare with the results of the preceding study on the 
growth in size of the cortical nerve cells in the albino rat brain, 
data were gathered for the cortical cells of the Norway rat also. 
According to my previous studies (Sugita, ’17 a, 718 a, ’18b), 
the measurements of the cerebral cortex in the Norway rat in 
thickness, in total number of cells, etc., have shown some inter- 
esting relations to the corresponding measurements for the 
Albino. Donaldson and Hatai (11) made a comparison of these 
two animals in respect of their body measurements and the size 
of the central nervous system, and concluded that the greater 
weight of the brain in the Norway rat is probably due to an en- 
largement of the constituent neurons rather than to an increase 
in their number. As my former study (Sugita, 718 b) has de- 
