26 NAOKI SUGITA 
(brain weight average 1.815 grams) is 1.90 mm. Here the al- 
bino cortex is taken as the standard for the determination of 
the percentage difference. For the comparison of each locality 
and the averages of each section, table 8 is to be consulted. It is 
remarkable that both in the sagittal and horizontal sections the 
34 = + — : 
| | | | | 
32 +—— 4+ — = a } 1 | 
} | 
| | | 
30! —+—_- 1 all i i | —;-—5—+ | ; | 
| | lo || | | 
28 =e + £. ns — 
| ° 
PO a SS ES eS ee eee 4 
| | J | | 
| ° } | | 
24; eh ee ech, EE --h -+ a 
| | | | 
| | | | 
|e = ——— wo al thea: 
| i | | 
20 a a L + top 
| . le 
48|- t T Te | i 7 
| | 
‘ae + . id 4 4 4 =e a all = zoe 
: eg ae | 
44} —_1 SaaS ete + ts ti 4 
| | | Vahezdlie | situs 
12/ {| oe (Peseel D ee > ee L eae 
10) — ails Soll ie ea weak os 
(see a | AP | 
pepeee) Sekaee | + — + — 4 = 
| | 
a6| | i = | = a th = 4 
| | | 
| | | 
ial oA ee ee on | ; 
| ‘i 
a2 —— -+—}_}__ {+ 
r) | | =i pe Jt | Ail | | 
LOPS A AS Gy di 18) ASN AOy 21 22 Seams 
Chart 2 Giving the corrected thickness of the cerebral cortex of the Norway 
rat in the sagittal section. Individual entries for the cortical thickness at lo- 
calities I and V, and the average thickness of thé sagittal section (localities I, II, 
III, IV and V) are given. Based on table 4. ° Cortical thickness at locality I. 
Corrected. Cortical thickness at locality V. Corrected. * Average thick- 
ness of the sagittal section. Corrected. 
percentage differences follow in the same order from the frontal 
to the occipital pole, rising towards the occipital pole.» The oc- 
cipital parts, represented by the pair of localities V and XIII, are 
the most developed in the Norway, surpassing the corresponding 
parts of the Albino by 15 and 28 per cent respectively. The 
pair of localities IV and XII, whose positions are adjoining, show 
also a marked excess in thickness, that is, 10 and 11 per cent 
