2 NAOKI SUGITA 
"17 a). To represent the cortex, the lamina pyramidalis and the 
lamina ganglionaris were selected. By the use of the ocular 
net-micrometer (with Zeiss Comp. Ocular 6 and Zeiss objec- 
tives 2 mm. and 4 mm.), the number of nerve cells in five ad- 
joining squares along the cortical band, each square 100 micra 
on a side, was counted in a given location. The numbers ob- 
tained were added together and then, by multiplying by two, 
was converted to the number in a unit area of 0.1 mm.? on the 
section. This value, the number of nerve cells in a slice of cor- 
tex, 0.1 mm.? in area and 10 micra thick (the thickness of the 
section) or 0.001 mm.* in volume, was then reduced to the number 
in this volume in the fresh condition of the brain. To make 
this reduction, I used as the correction-coefficient the cube of 
the reciprocal of the correction-coefficient obtained by the for- 
at iameter W.D i S ; 
ane ne diameter in fresh cerebrum a a a 
The diameter W.D on the slide 
previously employed, because the section on the slide was as- 
sumed to have shrunken in all three dimensions equally at the 
rate of the correction-coefficient and therefore a unit volume 
in the fresh condition would correspond to the volume of the 
unit on the slide multiplied by the cube of the reciprocal of the 
correction-coefficient. 
In the lamina pyramidalis, the pyramids are more densely 
crowded at the ectal than at the ental part of the layér, which 
adjoins the lamina granularis interna. I adjusted the upper 
line of the net-micrometer squarely on the border between the 
lamina zonalis and the lamina pyramidalis and counted the cell 
number included in a square, 100 micra on each side, at the ectal 
part of the layer, where the cells are crowded densely. If large 
blood vessels appeared in the microscopic field, I gave up such 
a field and counted an adjoining one where no large vessels 
were present. 
In the lamina ganglionaris the large ganglion cells are mixed 
with a number of small pyramids, almost equal in size to, or 
somewhat smaller than, the pyramids in the lamina pyramidalis. 
At first, the number of all the nerve cells, the large and small 
combined, was counted. Then the large ganglion cells, which 
