Abstract: A squeezing finger pressure is exerted on a trigger (100) carried by a finger-grip body (12) of a hypodermic syringe (10). The depressed trigger (100) displaces the free end of a cantilever spring (34) inwardly, moving a lock element (88) out from a radial opening (90) in a sidewall portion of the finger-grip body (12). This frees a compression spring (78) allowing it to drive an internal bushing (14), of which the cantilever beam spring (24) is a part, against a cartridge (28) within a barrel portion (16) of the syringe (10). The cartridge (28) carries a needle (18) at its forward end. The needle is moved into tissue in which an injection is to be made. A plunger (20) is moved against a piston (42) within the cartridge (28) to cause injection. The plunger (20) includes a penetrator rod (58) at its forward end.