contamination prior to the shielded cannula 80 engaging the pre slit septum 52 also the shield helps to align the piercing member with the pre slit septum the cylindrical blunt piercing member 98 can slidably engage the pre slit septum 52 best illustrated in fig4 b thereby extending through the preformed opening 66 therein as illustrated in fig4 b when the piercing member 98 slidably engages and pierces the septum 52 the region 52 a deforms by expanding into and filling at least in part the annular channel 62 the deformation facilitates insertion of the piercing member 98 through the slit 66 subsequent to the piercing member 98 slidably engaging the injection site 34 the interior region 90 of the syringe 82 is in fluid flow communication with the flow path 68 of the injection site 34 via flow paths 88 a and 98 a respectively of the syringe and the blunt piercing member 98 in this engagement condition the septum 52 seals completely around the piercing member 98 hence exterior gases liquids or airborne matter will be excluded from the channel 68 subsequent to infusing fluid from the syringe 82 into the fluid flow pathway 68 hence into the catheter 36 and the hand h of the patient the syringe 82 with lockingly engaged shielded cannula 80 can be slidably withdrawn from the injection site 34 subsequent to this withdrawal the septum 52 reseals the opening 66 therein the opening 66 will repeatedly reseal when the piercing member 98 is removed provided that the pressure in the septum 52 of the.