A syringe comprises a barrel with a plunger in slidable and sealing engagement therein, and a needle attached to one end of the barrel. The barrel has an aspiration device in the form of manually-operable resilient portions, which can be operated to cause a pressure differential in the barrel, the pressure differential then being used to perform aspiration. The resilient portions are preferably formed by localized reductions of wall thickness in the external surface of the barrel.本發明之注射器包括：配置有活塞之針筒、及連接於針筒一端之注針，針筒可滑動且密封地接合於針筒內。針筒具有手動彈性部型態之抽吸裝置，用以於針筒中產生一壓差，並藉由壓差達成抽吸，手動彈性部較佳係以局部縮減針筒之外表面壁厚而形成。
