The invention relates to a syringe (20) comprising a syringe barrel (15), an ejector unit (25) arranged at the distal end of the syringe barrel (15) with a plunger rod (17), a coupling part (37) and a plunger (16) and a syringe head (21) arranged at the proximal end of the syringe barrel (15) with a needle unit (12) which is arranged in a guide sleeve (5) and is slidable therein with a cannula (3) and a cannula holder (4) and a pinion (2), by means of which the needle unit (12) is axially movable, relative to a syringe barrel (15) from a rest position to an actuation position. At the distal end of the guide sleeve (5) a sealing element (7) is arranged. The pinion (2) has at least one guide knob (1), which can be brought into engagement optionally with one of two slide tracks (10) provided in the guide sleeve (5), wherein the slide tracks (10) are inclined in opposite directions.
