GROWTH OF THE CEREBRAL CORTEX 97 
of the cortex in the sagittal and the frontal section, following 
methods of measurement just described (part I) in the case of 
the Albino rat. Correction of the observed values to the 
values in the fresh condition of the material was also made 
by the use of the correction-coefficients obtained in the same 
way as those used for the Albino. 
This study was made between March and May, 1917, at the 
Wistar Institute of Anatomy and Biology. 
VII. MEASUREMENTS AND ENUMERATIONS 
K. Area of the cortex in the sagittal section (Norway rat) 
Table 8 shows the observed and corrected areas of the cere- 
bral cortex in the sagittal section of the Norway brain, also the 
data for the correction-coefhicient for each individual, and the 
correction-coeffiicient for each brain weight group. The method 
of measurement and the positions of the borderlines of the 
measured area have been already described in part I of this 
paper, so that the explanations need not be repeated here (fig. 
1). Chart 3 (graph s) has been plotted on the basis of table 8. 
L. Area of the cortex in the frontal section (Norway rat) 
Table 9 gives the observed and corrected areas of the cortex 
and the total area of the frontal section (one hemicerebrum) of 
the Norway brain with the data for the correction-coefficient 
for each individual and the correction-coefficient for each brain 
weight group. It gives also the percentage of the cortical area 
to the total area of the section. Chart 3 shows also in graphs 
(graphs F and f) the corrected data given in table 9. 
M. Number of nerve cells (Norway rat) 
Table 10 gives the observed and corrected number of nerve 
cells in a unit volume of 0.001 mm.’ (0.1 mm.” in area and 0.01 
mm. in thickness) at a fixed locality (locality VII) of the cortex 
in the frontal section, for each individual and for each brain 
weight group. The locality was chosen at a middle part of the 
cortical band in the frontal section as shown in figure 2, VII, 
