quality, or quantity which caused that divergence between
the human and the pithecoid stirpes, which has ended in the
present enormous gulf between them. It is no doubt
perfectly true, in a certain sense, that all difference of
function is a result of difference of structure; or, in
other words, of difference in the combination of the
primary molecular forces of living substance; and, starting
from this undeniable axiom, objectors occasionally, and
with much seeming plausibility, argue that the vast
intellectual chasm between the Ape and Man implies a
corresponding structural chasm in the organs of the
intellectual functions; so that, it is said, the
non-discovery of such vast differences proves, not that
they are absent, but that Science is incompetent to detect
them. A very little consideration, however, will, I think,
show the fallacy of this reasoning. Its validity hangs
upon the assumption, that intellectual power depends
altogether on the brain--whereas the brain is only one
condition out of many on which intellectual manifestations
depend; the others being, chiefly, the organs of the senses
and the motor apparatuses, especially those which are
concerned in prehension and in the production of articulate
speech.

A man born dumb, notwithstanding his great cerebral mass and his
inheritance of strong intellectual instincts, would be capable of few
higher intellectual manifestations than an Orang or a Chimpanzee, if he
were confined to the society of dumb associates. And yet there might
not be the slightest discernible difference between his brain and that
of a highly intelligent and cultivated person. The dumbness might be