In the hand are four bones, continuous with those of the fingers, called metacarpals (meta, beyond, carpus, wrist). They are covered by tendons on the back, and on the front by tendons, the muscles of the thumb and little finger, and skin pads.
There is a very slight movement like opening a fan between these bones. They converge on the wrist bones and are mortised almost solidly to them. The hand moves with the wrist. The dorsal tendons converge more sharply than the bones.
The short muscles of the hand, crossing only one joint, the knuckle, and moving the fingers individually, lie deep between the metcarpal bones and so are called interossei. They are in two sets, back and front, or dorsal and palmar. The palmar interossei are collectors, drawing the fingers toward the middle finger, and so are fastened to the inner side of each joint except that of the middle finger itself. The dorsal interossei are spreaders, drawing away from the centre, and so are fastened to both sides of the middle finger and to the outside of the other joints. In the thumb and little fingers the muscles of this set are called abductors, and being in exposed positions, are larger. That of the first finger forms a prominent bulge between it and the thumb; that of the little finger forms a long fleshy mass reaching to the wrist.
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