A quantitative stereological study of the area of cortical surface in the monkey, pig and cat cerebrum.

An unbiased stereological method (the 'vertical section') has been available since the 1980s for the area estimation of an arbitrary surface. Using this methodology, the ratio of the inner (folded) cerebral cortical surface area, to that of the outer surface, was estimated to be about 2 in Man. We have used the same morphometric techniques to study the cerebrum of seven monkeys, six pigs and six cats. The results demonstrated that the ratios were similar in monkeys (1.22 +/- 0.21, SD) and pigs (1.00 +/- 0.22), and that both were significantly larger than the ratio in cats (0.71 +/- 0.18).