nkey and Lemur
exhibits the characteristic arrangement of tarsal bones, possesses a
short flexor and short extensor muscle, and a 'peronaeus longus'. Varied
as the proportions and appearance of the organ may be, the terminal
division of the hind limb remains, in plan and principle of
construction, a foot, and never, in those respects, can be confounded
with a hand.

Hardly any part of the bodily frame, then, could be found better
calculated to illustrate the truth that the structural differences
between Man and the highest Ape are of less value than those between the
highest and the lower Apes, than the hand or the foot, and yet, perhaps,
there is one organ the study of which enforces the same conclusion in a
still more striking manner--and that is the Brain.

But before entering upon the precise question of the amount of
difference between the Ape's brain and that of Man, it is necessary that
we should clearly understand what constitutes a great, and what a small
difference in cerebral structure; and we shall be best enabled to
do this by a brief study of the chief modifications which the brain
exhibits in the series of vertebrate animals.

The brain of a fish is very small, compared with the spinal cord into
which it is continued, and with the nerves which come off from it: of
the segments of which it is composed--the olfactory lobes, the cerebral
hemisphere, and the succeeding divisions--no one predominates so much
over the rest as to obscure or cover them; and the so-called optic lobes
are, frequently, the largest masses of all. In Reptiles, the mass of
the brain, relatively to the spinal cord, increases and the cerebral
hemispheres begin to predominate over the other parts; while in Birds
this predominance is still more marked. The brain of the lowest Mammals,
such as the duck-billed Platypus and the Opossums and Kangaroos,
exhibits a still more definite advance in the same direction. The
cerebral hemispheres have now so much increased in size as, more or
less, to hide the representatives of the optic lobes, which remain
comparatively small, so that the brain of a Marsupial is extremely
different from that of a Bird, Reptile, or Fish. A step higher in the
scale, among the placental Mammals, the structure of the brain acquires
a vast modification--not that it appears much altered externally, in
a Rat or in a Rabbit, from what it is in a Marsupial--nor that the
proportions of its parts are much changed, but an app