NO. 
N XVI f 
N XVII f 
b 
d 
h 
N XVIII b 
d 
N XIX ¢ 
N XX e 
b 
N XXI f 
j 
N XXII 
N XXIII a 
GROWTH OF THE CEREBRAL CORTEX 
TABLE 2—Continued 
LITTER 
NO. 
BODY WEIGHT 
BODY LENGTH 
TAIL LENGTH 
Rh eh 
(4) f 
Lon) 
grams 
56.7 
73.9 
66.7 
98.3 
73.9 
71.8 
95.4 
125.0 
97.7 
I .8 
128.5 
134.0 
131.3 
167 °6 
167.6 
394.0 
394.0 
mm. 
129 
148 
138 
156 
143 
140 
155 
180 
152 
157 
256 
mm, 
109 
132 
112 
141 
124 
112 
130 
150 
139 
133 
153 
148 
151 
160 
160 
188 
178 
183 
190 
195 
193 
202 
202 
BRAIN WEIGHT 
grams 
1.613 
1.666 
1.674 
1.699 
1.663 
Leal 
als 
1.773 
ere) 
LeWAr 
1.815 
1.870 
1.843 
— 
953 
1.953 
008 
028 
018 
%® bo bo 
150 
.162 
156 
® bo bo 
2.345 
2.345 
But, according to the authors cited above, the marked difference 
between the two forms in body size does not appear during the 
period of rapid growth, but later, so that at maturity the Nor- 
way rat has a body weight 25 to 40 per cent above that of the 
For the same age however, the percent- 
ages of water in the central nervous system is just a trifle higher 
in the case of the Norway. Relative to the body weight, the 
Norway rat at maturity has a heavier brain than the albino rat, 
the difference being about 16 per cent in favor of the Norway. 
Albino rat of like age. 
