12. Abduction of Thumb Subject: Place the hand on a table with the palm up and the thumb slightly separated from the index finger. Abduct the thumb at the carpometacarpal joint by raising it vertically upward. Using your opposite hand, palpate the forearm and hand and identify as many muscles as possible. What is the prime mover? Explain the action of this muscle. 15. Opposition of the Thumb Subject: Press the thumb hard against the tip of the middle finger. Using your opposite hand, palpate and identify the prime movers. What are the prime movers? Explain the actions of these muscles..