5 cubic inches, the minimum 24 cubic inches; and, thirdly, after
making all due allowance for difference of size, the cranial capacities
of some of the lower Apes fall nearly as much, relatively, below those
of the higher Apes as the latter fall below Man.
Thus, even in the important matter of cranial capacity, Men differ more
widely from one another than they do from the Apes; while the lowest
Apes differ as much, in proportion, from the highest, as the latter
does from Man. The last proposition is still better illustrated by the
study of the modifications which other parts of the cranium undergo in
the Simian series.
It is the large proportional size of the facial bones and the great
projection of the jaws which confers upon the Gorilla's skull its small
facial angle and brutal character.
FIG. 16.--Sections of the skulls of Man and various Apes, drawn so as to
give the cerebral cavity the same length in each case, thereby
displaying the varying proportions of the facial bones. The line 'b'
indicates the plane of the tentorium, which separates the cerebrum from
the cerebellum; 'd', the axis of the occipital outlet of the skull.
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