230 NAOKI SUGITA 
natal growth (Sugita, 17a). The same statement is true for 
the localities VI, VII, and VIII in the frontal sections (based on 
the unpublished table 6b). The order in the rate of increase in 
the cortical thickness is an index of the grade of intensity in cell 
migration to those localities and of the growth impulse of the 
elements there. From previous studies (Sugita, 717 a), it was 
found that, as a rule, the cortical thickness decreases from the 
frontal to the occipital pole and from the dorsal to the ventral 
aspect, and the nearer a locality is to the ventricular wall or the 
matrix the more rapid the rate of increase in the thickness of the 
cortex. In underfed brains, the localities which show normally 
the higher rate of increase in thickness are also greater in the 
cortical thickness when compared with the standard. So, in the 
underfed, the cerebral cortex is generally thicker than the stand- 
ard for the same brain weight and thicker in each locality in pro- 
portion to the rate of increase in the thickness of that locality 
under normal conditions. 
In short, the growth in the cortical thickness in the case of the 
underfed is more advanced than that of the normal brain of the 
same weight, which is, of course, younger. 
18. A DISCUSSION ON THE RELATION BETWEEN CELL DENSITY AND 
THE COMPUTED VOLUME OF THE CEREBRAL CORTEX 
As stated earlier, the cell density of the cerebral cortex, repre- 
sented by the number of nerve cells in two unit volumes (NV), is, 
in the underfed Albino brain, under sixteen days in age, consid- 
erably higher than the standard for the same age, and accord- 
ingly the cell size in the underfed must be smaller than the stand- 
ard size and, by inference, the cell attachments also underde- 
veloped for the age. The relations between these data will be 
examined now according to my measurements as presented in this 
paper. 
The cortical area as measured in the sections from the under- 
fed brains proves to be slightly greater than the standard values 
for the same brain weight, but on the other hand, it is distinctly 
less in brains under sixteen days of age than the standard values 
