Abstract: A medical instrument comprises a needle which is movable between an extended operative position where the needle is exposed for use and a retracted inoperative position where the needle is covered so as to reduce the likelihood of inadvertent contact with the needle. The instrument also includes a needle biasing means which normally urges the needle toward its retracted position and an actuator movable between a position of interference with movement of the needle to its retracted position and a position out of interference with the needle to permit the needle biasing means to act on the needle and urge the same toward its retracted position.