GROWTH OF THE CEREBRAL CORTEX igs) 
quite unstained. The period during which the brain weight in- 
creases from 1.1 to 1.3 grams coincides with a transitional phase 
of the color. I regret that I have not been able to reproduce 
these distinctions of color for the illustration of this paper. 
These changes in color suggest that at the 20 to 30 day phase 
some chemical changes in the structure of the cell body and the 
nucleus have been occurring.’ At this phase of growth, the cells 
having attained nearly the full size, the rate of increase in size 
abruptly diminishes, suggesting that during this phase important 
changes have occurred. Myelination is proceeding very actively 
after the brain has attained the weight of 1.0 gram (Sugita, 717 a), 
and the fact that the cell bodies and nuclei of the pyramids de- 
crease in size as the brain weight passes 1.3 grams while the 
growth of the cell body and of the nucleus of the ganglion cells 
become very slow may have some connection with the myelin 
formation. 
Table 3 enables us to examine the measurements for the frontal 
and for the horizontal sections separately. Generally speaking, 
at the locality VII, measured in the frontal section (lines de- 
noted by F in table 3) and at the locality X measured in the 
horizontal section (see lines denoted by H in table 3), the cor- 
rected sizes of the cell body and of the nucleus show some differ- 
ences in the younger brains, but the sizes may be regarded on 
the whole as practically the same in these two localities in 
mature brains. If stated more minutely according to the data 
presented in table 3, the pyramids and the ganglion cells at 
locality VII (frontal section) grow in size somewhat more slowly 
as compared with those at locality X (horizontal section), so 
that in Groups IV to X the diameters are all smaller for the 
frontal section than for the horizontal section, in averaged 
values (see table 3). But if these slight discrepancies be not 
2 As noticed in tables 1 and 2, the size of the ganglion cells directly meas- 
ured on the slides shows a slight decrease during this phase (1.0 to 1.3 grams 
in brain weight), while, in corrected measurements given in table 3, there can- 
not be detected any diminution in cell size during the same phase. This de- 
crease in size of the ganglion cells on the slide may have some connection with the 
chemical changes occurring in the cytoplasm and karyoplasm, which cause 
different reactions to the reagents used for fixation. 
