A comparison of considerable interest is also that of the cranial
module or mean diameter, to the capacity of the same skulls. This
comparison reveals an important sex factor.[148] Relatively to the
module, the capacity is very appreciably smaller in the female than
it is in the male. This is a universal condition to which, so far as
known, there are occasional individual but no group exceptions. It
appears very clearly in the Eskimo. In 283 western male Eskimo skulls
in which we have so far measured the capacity,[149] the module averages
15.38 centimeters, the capacity 1,490 cubic centimeters; while in 382
female skulls thus far gauged the former averages 14.82 centimeters,
the latter 1,337 cubic centimeters. The percentage relation of the
capacity to the module, the numbers taken as a whole, is _96.8_ in the
males but only _90.2_ in the females. This means that relatively to the
external size of the skull the female Eskimo brain is 6.66 per cent
smaller. Similar sex disproportion exists in other American groups as
well as elsewhere. Some day when suitable data accumulate it will be of
much interest to study this condition on a wider scale.