595880 Disclosed is a syringe (31) and method for using the syringe (31) comprising at least one substance storage chamber (10) a hypodermic needle (18) a sheath (14) a biasing means, a guide slot (12) a follower element an automatically operable locking means and a recess. The hypodermic needle (18) defines the needle tip (19) and is in fluid communication with the substance storage chamber (10). The sheath (14) is displaced between a retracted (22) wherein the needle tip (19) is covered and an extended position (20) through biasing means. The follower element displaces along the guide slot (12). In the retracted position (22), the guide slot (12) defines a first position for locking the sheath (14). In the extended position (20), the guide slot (12) defines a second position for locking the sheath (14). The automatically operable locking means locks the sheath (14) in the extended position (20). An arcuate portion of the guide slot (12) leads to the second position wherein an extension of the sheath (14) displaces the follower element into the second position. The slot (12) defines a recess adjacent to the second position. The recess halts the follower element in response to retraction forces applied to the sheath (14) whilst locked in the extended position (20).
