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The thumb's ability to oppose the fingers of the hand is a complicated function made possible by the advantage taken of the united mobility of several joints and the composite action of several muscles. The opposition is chiefly the result of two types of movements: angulatory motion and rotary motion. If we watch our own thumbs yerforming opposition we will see that the top of the thumb describes a circular arc of about 120", i.e. the sum of the angulatory motion. The thumb then rotates at the same time about go", this we can ascertain

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