Before we can discuss the first point with advantage we must consider
with some attention, and compare together, the structure of the human
hand and that of the human foot, so that we may have distinct and clear
ideas of what constitutes a hand and what a foot.

The external form of the human hand is familiar enough to every one. It
consists of a stout wrist followed by a broad palm, formed of flesh,
and tendons, and skin, binding together four bones, and dividing into
four long and flexible digits, or fingers, each of which bears on the
back of its last joint a broad and flattened nail. The longest cleft
between any two digits is rather less than half as long as the hand.
From the outer side of the base of the palm a stout digit goes off,
having only two joints instead of three; so short, that it only reaches
to a little beyond the middle of the first joint of the finger next it;
and further remarkable by its great mobility, in consequence of which
it can be directed outwards, almost at a right angle to the rest. This
digit is called the 'pollex,' or thumb; and, like the others, it bears a
flat nail upon the back of its terminal joint. In consequence of the
proportions and mobility of the thumb, it is what is termed
"opposable"; in other words, its extremity can, with the greatest ease,
be brought into contact with the extremities of any of the fingers; a
property upon which the possibility of our carrying into effect the
conceptions of the mind so largely depends.

The external form of the foot differs widely from that of the hand; and
yet, when closely compared, the two present some singular
resemblances. Thus the ankle corresponds in a manner with the wrist;
the sole with the palm; the toes with the fingers; the great toe with
the thumb. But the toes, or digits of the foot, are far shorter in