GROWTH OF THE CHREBRAL CORTEX so 
chart we see that the cortical volume increases more rapidly 
than the entire cerebral volume, until the brain attains the weight 
of 1.17 grams (20 days) (see crosses in chart 2). If we take 
these marks as the starting points, then the cerebral volume 
increases to about 1.7 times at full maturity and in the same 
way the cortical volume increases to about 1.4 times compared 
with the value at twenty days (table 6). So, it may be stated 
that after twenty days the increase in cortical volume becomes 
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Of 02B03 04 05 06 07 08 09 10 ff 12 13 14 15 46 17 18 19 20 gs 
Chart 2. Showing the ratios of the values for the cortical volume, the volume 
of the cerebrum, the cell density in two unit volumes and the computed number 
of nerve cells in the entire cerebral cortex of the albino rat, according to the 
brain weight. e « LWT, The ratios of the computed volume of the cerebral 
cortex, the volume at birth being taken as the unit. Based on the data in table 
6. . LWH, The ratios of the volume of the entire cerebrum, 
the volume at birth being taken as the unit. Based on the data presented in a 
former paper (Sugita, 717) and given also in table 6. X——XN, The cell den- 
sity in two unit volumes of the cortex. Based on the data given in column C, 
table 7, as N, and plotted here according to the values corresponding to one one- 
hundredth of the number given in column C, table 7. *— *—*NLWT, The 
ratios of the computed number of nerve cells in the entire cortex, the value at 
birth being taken as the unit. Here the unit chosen on the ordinate is 5. The 
data are given in column E, table 7. 
