| 摘要 |
Devices for extracting blood which comprises a cylinder having at one end a removable closure member carrying a connection piece for a cannula and an end wall at the other end. A piston is guided in the cylinder in an air-tight manner and a piston rod guided in a central bore in the end wall is releasably attached to an extension of the piston. The end wall forms a rigid stop for the retracted piston and an annular sleeve concentrically surrounding the central bore in the end wall serves for the purpose of receiving and retaining the piston extension, the space between a piston seal and the zone of contact between the extension and annular sleeve being vented when the piston is in its retracted state.
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