32 
NAOKI SUGITA ~ 
TABLE 8 
A comparison of the cortical thicknesses at each locality and on the average, in the 
adult Norway and the albino brains of the same absolute weight. 
The measure- 
ments used here are average values of Groups N XVI-N XX and Groups X VVI-XX 
respectively, taken from tables 4 to 6 of this paper and tables 6 to 8 (Sugita, ’17a). 
The corresponding brain weights are 1.844 grams in the Norway and 1.815 grams 
The thickness of the Albino cortex is always taken as the stand- 
in the Albino. 
ard for computing the percentage differences 
SECTIONS 
LOCALITIES 
THICKNESS OF THE CORTEX 
CORTEX OF THE 
NORWAY RAT EX- 
Norway rat Albino rat CEE DSSS 
mm. mm. per cent 
Locality I 2.84 2.80 1.4 
IL 2.06 1.92 Tos 
Sagittal III 1.82 1.74 4.6 
IV 1.51 1.36 10.0 
V 1.37 1.19 155,11 
Average........ 192, 1.80 6.7 
Locality VI Aral 1.84 14.8 
Frontal VII 2.28 2.18 4.6 
Vill 1.73 1.59 8.9 
Average.:...... 2.04 1.87 9.1 
Locality IX 3.09 3.08 0.3 
x E23 2.06 8.2 
Horizontal XI 2.10 2.04 3.0 
XII 1.90 Ia ileal 
XIII 1.63 2% 28.3 
Average...... Y 2.19 2.03 8.0 
General average ...........-.- 2.05 1.90 8.0 
two forms is made so as to bring those of approximately the 
same age on the same line of the table. 
It will be seen by these 
comparisons that the Norway rat brain, if paired with the albino 
rat brain of like age, shows almost the same value of the percent- 
age of water, while the brain weight differs by 16 to 20 per cent 
in favor of the Norway rat brain, the weight of the Norway brain 
being taken as the standard. 
So, from the point of view of age, a Norway rat brain should 
be in the same phase of development with an albino brain, 
