GROWTH OF THE CEREBRAL CORTEX 259 
Bevan Lewis (79) has given as the average depth of the 
human cortex the figures as high as 4.84 to 5.70 mm., a higher 
value even than that of Kaes. His results for both the pig and 
rabbit cortex were also very high, compared with those obtained 
for other mammals. These results suggest that his technique, 
which he claims gives the natural depth of the cortex, is likely 
to produce very high values. 
Reviewing the table (table 8), the values for the cortical thick- 
ness given for a fixed part of the hemisphere by different authors 
are by no means in accord; the results by Brodmann stand close 
to the results by Donaldson, while those given by Campbell are 
the lowest, less than one-half the values given by Lewis. These 
differences are probably due mainly to differences in technique 
and are not to be attributed to variations within the same species, 
as the series of Donaldson (table 7) and my previous study 
(Sugita, 717 a) both have shown that individual variations in 
cortical thickness, obtained by the use of the same technique, 
are low as compared with the variations for other body meas- 
» urements. 
On the average, the figures given by Donaldson and Brodmann 
are fairly close and the former being somewhat lower, probably 
because Donaldson took the average from the values at the 
summit and at the sides of the gyrus, while Brodmann has meas- 
ured the thickness at the summit only. The figures given by 
Hammarberg and Campbell are low, probably owing to the 
shrinkage of the material during preparation, as may be in- 
ferred from the descriptions by the authors and from the studies 
on the effects of fixing fluids by King (10) and by me (Sugita, 
Aliza, 13° b, 718 'e) 
Despite the apparent irregularity among the figures given for 
the cortical thickness at different localities by the several au- 
- thors, as shown in table 8, there are some general relations which 
are fairly clear. If we examine table 9 in which has been en- 
tered for each region the average thickness obtained by each 
author, it may be safely said that this table (and also table 6 
for the monkeys) shows that in man (and the primates) the 
cerebral cortex differs normally according to locality. The 
