A syringe including: - a syringe body extending along a longitudinal axis from a lower end to an upper end, the lower end of the syringe body allowing the fixation of a needle or a cannula and the upper end of the syringe body having an upper opening allowing the introduction of a plunger into the syringe body, the syringe body having an inner wall and including at least one first stop located along the inner wall of the syringe body near the upper opening, the first stop being adapted to leave at least one first blank surface on the inner wall of the syringe body, and - a plunger sliding along the inner wall of the syringe body along the longitudinal axis, the plunger comprising a plunger head and an operating rod connected to the upper end of the plunger head, the upper end of the plunger head being directed towards the upper opening of the syringe body, the operating rod of the plunger including, on its outer surface, at least one first rack arranged longitudinally along the operating rod, the first rack comprising protruding teeth, the first stop and the protruding teeth being shaped and constituted so as, during the upward movement of the plunger in the syringe body from a low position where the plunger head is near the lower end of the syringe body to a high position where the plunger head is near the upper end of the syringe body, when the first stop and the first rack are opposite to each other, to allow a tooth-by-tooth upward movement of the plunger along the syringe body, the syringe being characterized in that the first stop and the protruding teeth are also shaped and constituted so as to prevent any downward movement of the plunger under the effect of a push on the operating rod, but to disengage the first rack by rotation of the plunger in the syringe body about the longitudinal axis to bring the first rack opposite the first blank surface of the inner wall of the syringe body, and, wherein the plunger head includes: - a terminal part facing the lower end of the syringe body, the terminal part being such that it prevents any full disengagement of the plunger from the syringe body thanks to a locking by the stop(s), and - a base, connected to the terminal part, comprising at its periphery at least one first notch and at least one first longitudinal groove, the first notch and the first longitudinal groove of the base being shaped and constituted so as to allow the upward movement and the holding of the plunger in the high position when the first groove is opposite the first stop, and to prevent any downward movement of the plunger along the syringe body, but to disengage the plunger head by rotation of the plunger in the syringe body about the longitudinal axis to bring the first longitudinal groove opposite the first stop. - a syringe body extending along a longitudinal axis from a lower end to an upper end, the lower end of the syringe body allowing the fixation of a needle or a cannula and the upper end of the syringe body having an upper opening allowing the introduction of a plunger into the syringe body, the syringe body having an inner wall and including at least one first stop located along the inner wall of the syringe body near the upper opening, the first stop being adapted to leave at least one first blank surface on the inner wall of the syringe body, and - a plunger sliding along the inner wall of the syringe body along the longitudinal axis, the plunger comprising a plunger head and an operating rod connected to the upper end of the plunger head, the upper end of the plunger head being directed towards the upper opening of the syringe body, the operating rod of the plunger including, on its outer surface, at least one first rack arranged longitudinally along the operating rod, the first rack comprising protruding teeth, - a terminal part facing the lower end of the syringe body, the terminal part being such that it prevents any full disengagement of the plunger from the syringe body thanks to a locking by the stop(s), and - a base, connected to the terminal part, comprising at its periphery at least one first notch and at least one first longitudinal groove,