the highest animal below him. Differences in
the mechanical organs, such as the perfection of the human hand as an
instrument, or the adaptability of the human voice to the expression of
human thought, are indeed of great value. But they have not of
themselves such value, that to endow an ape with the hand and vocal
organs of a man would be likely to raise it through any large part of
the interval that now separates it from humanity. Much more is to be
said for the view that man's larger and more highly organized brain
accounts for those mental powers in which he so absolutely surpasses the
brutes.

The distinction does not seem to lie principally in the range and
delicacy of direct sensation, as may be judged from such well-known
facts as man's inferiority to the eagle in sight, or to the dog in
scent. At the same time, it seems that the human sensory organs may have
in various respects acuteness beyond those of other creatures. But,
beyond a doubt, man possesses, and in some way possesses by virtue of
his superior brain, a power of co-ordinating the impressions of his
senses, which enables him to understand the world he lives in, and by
understanding to use, resist, and even in a measure rule it. No human
art shows the nature of this human attribute more clearly than does
language. Man shares with the mammalia and birds the direct expression
of the feelings by emotional tones and interjectional cries; the
parrot's power of articulate utterance almost equals his own; and, by
association of ideas in some measure, some of the lower animals have
even learnt to recognize words he utters. But, to use words in
themselves unmeaning, as symbols by which to conduct and convey the
complex intellectual processes in which mental conceptions are
suggested, compared, combined, and even analysed, and new ones
created--this is a faculty which is scarcely to be traced in any lower
animal. The view that this, with other mental processes, is a function
of the brain, is remarkably corroborated by modern investigation of the
disease of aphasia, where the power of thinking remains, but the power
is lost of recalling the word corresponding to the thought, and this
mental defect is found to accompany a diseased state of a particular
locality of the brain (see APHASIA). This may stand among the most
perfect of the many evidences that, in Professor Bain's words, "the
brain is the principal, though not the sole organ of mind." As the
brains of