106 NAOKI SUGITA 
TABLE 12 
Comparison of the Norway rat brain with the Albino rat brain of like weight in the 
areas of the cortex,in the sagittal and the frontal sections and in the area of the 
total frontal section. The data were taken fram tables 1, 2, 8 and 9 
Gene | sore ay AREA OF 
Saar cioee 2 ae ar meu mRonraL [TON RCTION 
Albino | Norway| Albino | Norway| Albino |Norway| Albino | Norway 
grams | grams | mm. mm2 | mm? mm? mm.2 | mm.2 
XI AL e638 2OeG e450 Mle S22R Si Ayden 
XII 1.253 26.1 23.0 47.2 
XIII 1.335| 1.869) 27.6.) 27.5 | 238.2 | 24:2 | 50.2 | 4922 
XIV 1.445} 1.480) 28.2-| 29.2 | 24.8 | 25.4 | 52.3 | 52.7 
XV 1.554 1.542) 28.7 | 28.4 | 24.3 | 26.3 | 54.0 | 55.1 
xeViT 1.656) 1.629) 29.2 | 30.5 | 24.3 | 27.2 | 54.9 | 66.7 
XVII 1.726) 1.789) 31.1 | 31.8 | 24.6 | 27.8 | 56.4 | 58.9 
XVIII 1.839] 1.829) 32.8 | 33.0 | 26.0 | 29.6 | 58.9 | 62.4 
XTX 1.924) 1.972) 32.3 | 33.8 | 24.8 | 28.2 | 57.0 | 61.4 . 
xX 2.054) 2.052) 33.7 | 33.8 | 24.9| 28.2 | 63.4 | 68.8 
xXXI 2.172 35.0 29.5 ; 67.2 
XXII 
XXIII 2.345 35.7 
Average for Groups XIII- 
RONEN cas oe hee 12692) 227695) 30.5437 (0) 2463 2727 95529 o7 25! 
The total area of the frontal section is also slightly in favor 
of the Norway (table 12). 
P. Percentage of the area of the cortex to the votal area of the frontal 
section (one hemicerebrum). Norway rat compared 
with the Albino 
As for the percentage of the cortical area to the total area of 
the section, a comparison between the two forms is interesting. 
In the Albino this percentage value increases from birth to a 
brain weighing 0.7 to 1.2 grams when it attains the value of 
about 48 per cent (table 2), but in the Norway the highest per- 
centage is attained in brains weighing 1.1 to 1.8 grams. This 
indicates that the cortical organization is more retarded in the 
Norway, if the brain weight be taken as the basis of comparison. 
In a fully mature Norway brain (from Group N XX onwards, 
