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 proportion than the
digits of the hand, and are less moveable, the want of mobility being
most striking in the great toe--which, again, is very much larger
in proportion to the other toes than the thumb to the fingers. In
considering this point, however, it must not be forgotten that the
civilized great toe, confined and cramped from childhood upwards, is
seen to a great disadvantage, and that in uncivilized and barefooted
people it retains a great amount of mobility, and even some sort of
opposability. The Chinese boatmen are said to be able to pull an oar;
the artisans of Bengal to weave, and the Carajas to steal fishhooks, by
its help; though, after all, it must be recollected that the structure
of its joints and the arrangement of its bones, necessarily render its
prehensile action far less perfect than that of the thumb.

But to gain a precise conception of the resemblances and differences of
the hand and foot, and of the distinctive characters of each, we must
look below the skin, and compare the bony framework and its motor
apparatus in each (Figure 18).

(FIGURE 18.--The skeleton of the Hand and Foot of Man reduced from Dr.
Carter's drawings in Gray's 'Anatomy.' The hand is drawn to a larger
scale than the foot. The line 'a a' in the hand indicates the boundary
between the carpus and the metacarpus; 'b b' that between the latter and
the proximal phalanges; 'c c' marks the ends of the distal phalanges.
The line "a' a'" in the foot indicates the boundary between