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 the tarsus
and metatarsus; "b' b'" marks that between the metatarsus and the
proximal phalanges; and "c' c'" bounds the ends of the distal phalanges;
'ca', the calcaneum; 'as', the astragalus; 'sc', the scaphoid bone in
the tarsus.)
The skeleton of the hand exhibits, in the region which we term the
wrist, and which is technically called the 'carpus'--two rows of closely
fitted polygonal bones, four in each row, which are tolerably equal in
size. The bones of the first row with the bones of the forearm, form the
wrist joint, and are arranged side by side, no one greatly exceeding or
overlapping the rest.
The four bones of the second row of the carpus bear the four long bones
which support the palm of the hand. The fifth bone of the same character
is articulated in a much more free and moveable manner than the others,
with its carpal bone, and forms the base of the thumb. These are called
'metacarpal' bones, and they carry the 'phalanges', or bones of the
digits, of which there are two in the thumb, and three in each of the
fingers.
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