Syringe

A syringe comprising:

• a syringe outer tube possessing a tubular shape to be filled with a liquid and provided with a spout through which the liquid passes at a distal end portion of the spout;
• and
• a cap mounted to the spout,
• wherein the cap includes a cap main body which seals the spout in a liquid-tight manner, a ring-shaped mounting section which is disposed on a proximal end side of the cap main body and is mounted onto an outer circumferential portion of the spout, and a breakable breaking section serving as a link which links the cap main body and the mounting section so that rotation of the cap main body relative to the spout is transmitted to the mounting section by way of the breaking section such that the ca p main body and the mounting section rotate together until the breaking section breaks and thus releases the link between the cap main body and the mounting section,
• one of an inner circumferential portion of the mounting section and the outer circumferential portion of the spout includes at least one projection, while the other includes a groove in which the projection is positioned and which has an inclined section that is inclined in relation to an axis of the other, and
• when the cap is rotated relative to the syringe outer tube around an axis of the syringe outer tube while the breaking section links the cap main body and the mounting section, the mounting tube rotates and so the projection moves along the inclined section of the groove to cause the mounting section to move in a direction away from the cap main body and in a proximal direction relative to the spout such that the breaking section is pulled to break the link between the cap main body and the mounting section, thereby separating the cap main body from the mounting section so that the cap main body thus separated fro n the mounting section cannot be mounted again onto the spout.