CEREBRAL CORTEX: WILD NORWAY 



365 



(a) Comparison with Albino. Although the values given in 

 columns G and H, table 197 are relative, they show how the volume 

 of the cortex increases with brain weight in each strain, and the 



TABLE 197 



Showing the computed volume for the entire cerebral cortex of the Norway rat brain, 

 calculated by the formula: L.F. X W. D X T X 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, 

 '18). These values are paired with the corresponding values for the cortical volume 

 of the Albino and the ratios between them calculated 



NORWAY RATS 



Brain 

 weight 

 group 



NXI 



NXII 



NXIII 



NXIV 



NXV 



NXVI 



NXVII 



N XVIII 



NXIX 



NXX 



NXXI 



Brain 

 weight 



grams 



1.163 



1.369 

 1.430 

 1.537 

 1.629 

 1.739 

 1.829 

 1.972 

 2.052 

 2.172 



Com- 

 puted 

 volume 

 of 

 cerebrum 



L.GX 

 W.DXHt. 



mm.^ 



156 



182 

 185 

 194 

 203 

 218 

 226 

 241 

 249 

 264 



L.F 



in fresh 

 brain 



mm. 

 12.2 



13.1 

 13.2 

 13.5 

 13.6 

 13.9 

 14.3 

 14.6 

 14.7 

 15.1 



W.D 



in fresh 

 brain 



mm. 



12.7 



13.0 

 13.2 

 13.4 

 13.7 

 13.9 

 14.2 

 14.3 

 14.4 

 14.9 



average 



cortical 



thickness 



1.75 



1.85 

 1.90 

 1.93 

 1.98 

 2.01 

 2.01 

 1.99 

 1.94 

 2.04 



Average (Groups N XIII-N XX) 386. 92 



L.FX 

 W.D XT 



xc 



Com- 

 puted 

 volume 

 of cortex 



m.m.' 



281.00 



326.51 

 343.09 

 361.83 

 382.32 

 402.47 

 423.00 

 430.57 

 425.59 

 475.66 



ALBINO RAT 



H 



Corre- 

 sponding 

 computed 

 volume 

 of the 

 Albino 

 cortex, of 

 the same 

 group 

 number 



288.93 

 304. 51 

 314.03 

 329.71 

 345.86 

 359.30 

 365.08 

 397.96 

 390.39 

 393.15 



361.94 



Ratio 



of cortical 



volume 



of the 



Norway 



to that of 



the 



Albino 



0.973 



1.040 

 1.040 

 1.046 

 1.064 

 1.102 

 1.063 

 1.103 

 1.083 



1.069 



*T, here entered, is the mean value of Ts and Tf, 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, '18 a). 



relation between the volume in the Norway and in the Albino at 

 like brain weights. As a result of the greater thickness and area 

 of the Norway cortex the volume exceeds that of the Albino by 

 about 7 per cent. 



