264 NAOKI SUGITA 
fine, and stained by Nissl’s method). The mean value of the 
cortical thickness at the summit of the gyrus was 3.55 mm., 
or within 10 per cent the value obtained by Brodmann at the 
same locality in the adult brain and on a section similarly pre- 
pared and measured (table 8). So far, then, as this observation 
goes, it helps to support my conclusion presented earlier that the 
human cortex has attained nearly its full thickness at the age of 
fifteen months (Sugita, 717 a). 
VII. THE BRAIN WEIGHT, THE CORTICAL VOLUME, AND THE BODY 
WEIGHT 
Dhéré and Lapicque (’98) and DuBois (98 a, ’98 b), working 
independently, found several important relations existing be- 
tween the body and the brain weights in man and a number of 
other vertebrates. Recently DuBois (713) has obtained results 
which he has formulated in following terms: 
1) In species of vertebrates that are alike in organization of 
their nervous system and their shape, but differ in size, and also 
in the two sexes of one and the same species, the quantity of the 
brain increases; A) as the quotient of the superficial dimension 
divided by the cube root of the longitudinal dimension. B) as 
the product of the longitudinal dimension by the square of its 
cube root. 
2) In individuals of one and the same species and of the 
same sex, but differing in size, the quantity of brain increases 
as the square of the cube root of the longitudinal dimension of 
the body. 
So, briefly stated, 1) reads: in any species of vertebrates that 
are equal in organization, in form of activity and in shape, the 
weights of the respective brains are proportional to the 0.55 power 
3 According to a study by Fuchs (’83), the child is born without any mye- 
linated fibers in the cerebral cortex. Inthe laminazonalis the first myelination 
appears at five months, in the lamina pyramidalis at the end of the first year, 
while in the innermost layers we see some faintly stained fibers at two months. 
The fibrae arcuate (association fibers) appear clearly at seven months. Later 
the myelinated fibers increase in caliber and number as the age advances, and 
at eight years they attain nearly the appearance which they have in the adult 
cortex. 
