in both the distal and proximal directions near its proximal end the lumen 50 widens at a neck 52 to take on a larger diameter cross section proximal of the neck 52 correspondingly the everting tube 48 widens to form a stub 54 disposed within the larger diameter portion of the lumen 50 the neck 52 coacts with the stub 54 to limit the travel of the everting tube 48 in the distal direction 0043 fig7 and 8 show the proximal end 28 of the sheath 24 in detail note that fig7 and 8 are oriented 90 u00b0 with respect to one another so that fig7 may be considered a side view and fig8 a top view a longitudinal slot 56 is formed in the wall of the cannula 40 near the proximal end 28 the slot 56 permits an allen screw 58 to extend from a threaded hole 60 in the stub 54 beyond the external wall of the cannula 40 and into a space 62 formed by a radial groove 64 in the everting knob 26 between distal and proximal walls 66 68 with the screw 58 in place one can cause the everting tube 48 to move in either the distal or proximal direction by manipulating the everting knob 26 if the everting knob 26 is rotated so as to advance in the distal direction the proximal wall 68 of the radial groove 64 bears on the screw 58 as the everting knob advances distally causing the everting tube 48 to move distally within the lumen 50 similarly if the everting knob 26 is rotated so as to advance in the proximal direction the distal wall 66 of the radial groove.