GROWTH OF THE CEREBRAL CORTEX sab 
TABLE 15 
Showing the computed volume for the entire cerebral cortex of the Norway rat brain, 
calculated by the formula: L.F X W. DX TX C for each brain weight group, 
C being a fixed coefficient used to convert the computed volume of the Norway 
cortex so as to make it comparable with that of the Albino (C = 1.036). The 
computed volume of the cerebrum is quoted from my previous presentation (Sugita, 
718). These values are paired with the corresponding values for the cortical 
volume of the Albino and the ratios between them calculated 
NORWAY RATS ALBINO RATS 
A B G | D E F G H I 
; ; Corre- 
sponding Ratio 
Computed L. I’ & |ecomputed | of cortical 
; f ; volume LF W.D flee W. DXT| volume volume 
Brain weight) Brain of ; tr 7 smireaet average KIC of the of the 
group weight cerebrum a Ares ; GE inesh cortical |Computed| Albino Norway 
ES Ga yea open thickness | volume | cortex, of | to that of 
W.DXHt. of cortex | the same the 
group Albino 
number 
grams mm. mm. mm. mm. mm 3 mm .3 
N XI 1.1638 156 12.2 PAA 1S 281.00 | 288.93 0.973 
N XII 304.51 
N XIII 1.369 182 Sel 13.0 1.85 326.51 | 314.03 1.040 
N XIV 1.480 185 1S )2 133,73 1.90 343.09 | 329.71 1.040 
N XV 1 BY 194 13.5 13.4 1.93 361.83 | 345.86 1.046 
N XVI 1.629 203 13.6 1133-7 1.98 382.32 | 359.30 1.064 
N XVII 1739 218 13.9 13.9 2.01 402.47 | 365.08 1.102 
N XVIII 1.829 226 14.3 14.2 2.01 | 423.00 | 397.96 1.063 
N XIX 1.972 241 14.6 14,3° ‘|| 1299 430.57 | 390.39 1.1038 
N XX 2.052 249 14.7 14.4 1.94 425.59 | 393.15 1.083 
N XXI MsMG 2645) 15 14.9 2.04 475.66 
Aer amen (GOW Ss) NjeXGlolIESINi BNOXN@ ene es ee 386.92 | 361.94 1.069 
1'T, here entered, is the mean value of Ts and T,, previously given in tables 
11 and 13 and is not the general average thickness of the cortex of the sagittal, 
frontal and horizontal sections formerly presented in my fourth paper in this 
series (Sugita, 718 a). 
data (L. F x W. D x T) according to the brain weight groups, 
quoted from part I. In table 15 the ratios show the volume of 
the cortex in the Norway to be greater (1.040 to 1.103) in all the 
comparisons for brain weights above Groups XIII (brain weight 
1.37 grams). The average value is about 1.07. In Group XI 
(brain weight 1.17 grams), the ratio for the Norway is less than 1. 
At this weight the Norway brain is regarded as less mature than 
