GROWTH OF CEREBRAL CORTEX 7 
Ht. in the Norway cerebrum is greater on the average than that 
of the Albino of the same age by ca. 0.6mm. As was to be ex- 
pected the excess in the dimensions of the Norway brain are 
greater in part B, Chart 2, where the brains are compared ac- 
cording to age, because at like ages the Norway brain is heavier. 
The chief point of interest brought out by this comparison is 
the similarity in the direction of the corresponding curves for the 
two forms and the fact that the age at which L. G crosses W. B 
in the Albino is approximately the age at which these diameters 
come nearest to crossing in the Norway. 
Table 3 A gives the relative volumes of the cerebrum in each 
brain weight group of the Norway rat, obtained by the formula: 
nn B 
; 418 = 
| | 
—4 ed a —— | —l. 
alee. | | | 
| 
| 
5 }-—_+—_+—__+__+ 
| 
| T 
| | 
j++}. 1 _} + 5 = 4 + = = ——— 
| | | 
| | 
| | 
| 
| 
— 
4 : | us| 12 = | | | a a es _! x | 
“il 12 15 14 15 16 17 18 19 20 21 22 23 m= 09 10 If 12 13 44 45 ie iT #8 19 gr 
Chart 2 Giving a comparison of the cerebral measurements (W.B, L. G and 
Ht.) of the Norway and the albino rats. Part A was plotted according to the ob-. 
served weight of the brain for each brain weight group of the Norway rat. Part 
B was plotted according to the corresponding weight of the brain in the Albino 
of the same age, the Albino brain weights being obtained by reducing the observed 
weight of the Norway brain by 18 per cent. The measurements for the Norway 
cerebrum were based on table 2 of this paper and the measurements for the Al- 
bino cerebrum were based on table 3 of the first paper of this series (Sugita 717). 
—-* o— WB(Norway) —— W.B(Albino) 
e----- @ O----0 EEG “) see ss L.d( “ ) 
