A surgical apparatus for penetrating tissue includes an outer member defininga longitudinal axis and having an outer peripheral wall and an inner member atleast partially disposed within the outer member. The inner member includesa penetrating member adjacent the distal end of the outer member. The penetratingmember has a substantially annular peripheral edge adapted to penetrate tissue.The inner member and the outer member are adapted for relative longitudinal movementbetween first and second longitudinal positions. In the first position, theannular peripheral edge of the penetrating member is substantially confinedwithin the outer peripheral wall of the outer member and wherein, in the secondposition, the annular peripheral edge is at least partially exposed from theouter peripheral wall to facilitate penetration through tissue.
