Abstract: Syringe consisting of a body in which is disposed a piston (2) of the kind including at least two racks (53, 54) fitting onto the body and at least one lug carried by the piston (2), each of the racks being capable of being shifted in a single direction in relation to a lug. According to the invention, the syringe includes two lugs (63, 64) carried by a yoke (6) which straddles the piston (2), and is rotatably movable about the piston's axis. The lugs (63, 64) are driven into translation by the piston (2) while rotating freely in relation to the latter.