Abstract: A single use hypodermic syringe is provided and has a reversible stop member which permits movement of the plug in one direction but not in the opposite direction so that the plug may be moved in the direction to aspirate fluid in the hypodermic syringe during which the reversing member moves into a reversing chamber so that it may be reversed to permit movement of the plug to eject fluid from the hypodermic syringe but to prevent movement of the plug in the opposite direction after the ejection of fluid has been commenced and after all of the fluid has been ejected.

Abstract: A single use disposable hypodermic syringe is provided and comprises a hollow elongated barrel having a generally cylindrical inner surface having a longitudinal axis, an open end and another end having an annular shoulder with a central opening in which a cannula is positioned. A piston and a piston rod are provided and a plug formed from a clear, transparent and resilient but slightly compressible material is releasably secured to the piston and is in sealing relationship with the inner surface of the hollow elongated barrel and, when moved in axial directions functions to aspirate fluid into the hollow elongated barrel or to eject fluid from the hollow elongated barrel.