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The rod and ball construction of the hand derives from its internal skeletal structure. It is the skeletal structure which is plainly responsible for the hard, bony surface throughout the upper palm and fingers (above).
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The hand, like the foot, gives us a set of rod and ball constructions in the alternating bone shanks and knuckle capsules of the fingers.
The fingers are remarkably longer and more flexible than the toes. They tend to override the plane of the palm easily in active contrapositions which are not possible in the passive, closed toe system of the foot.
