A pre-slit injection site includes a housing with a flow path therethrough. A first end of the housing carries a pre-slit septum. One form of a blunt cannula, usable with the injection site, carries a locking member. When the pre-slit injection site slidably receives the blunt cannula, the locking member latches to the injection site and creates a mechanically coupled unit. Another form of the cannula includes a tube having a tapered distal end region and having elongate discharge slots for reducing contact surface area and for directing the flow laterally out of the cannula. The cannula may also include a rounded lead post, an annular barb, and axially oriented grooves.