| 摘要 |
A hypodermic syringe which can be filled with liquid medication for injection into a subject only from a container of the liquid under pressure greater than the ambient pressure around the syringe includes a moveable piston in a cylinder and an injection needle extending from one end of the cylinder defining a liquid dosage space between the piston and the needle and on the other side of the piston in the cylinder is a piston stem that extends from the other end of the cylinder and is manipulated by the user to inject a liquid from the dosage space under the force of the piston out of the needle, the piston and the piston stem being adapted so that the stem can be manipulated to push the piston toward the needle, but the stem cannot be manipulated to pull the piston away from the needle, and the position of the stem in the cylinder can be adjusted at any of a plurality of positions that limit the travel of the piston away from the needle and so limit the volume of the liquid dosage space defined between the piston and the needle. In preferred embodiments, the limitation adjustment is continuously variable at all values of dosage space volume from substantially zero to a predetermined maximum volume.
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