Syringe

A syringe comprising:

• (a) a plunger including a plunger head and a shaft;
• (b) a barrel;
• (c) a restrictor mechanism located between the shaft and the barrel and including (i) a first part having an outer member engaged with the barrel and oriented so as to limit movement of the first part with respect to the barrel in a first direction, and (ii) a second part;
• (d) the restrictor mechanism and/or shaft carrying a formation for limiting movement of the restrictor mechanism with respect to the plunger in said first direction;
• (e) the restrictor mechanism being provided with a further member oriented or arranged so as to restrict movement of the restrictor mechanism with respect to one of the barrel and plunger shaft in a second direction opposed to said first direction;
• and
• (f) a latch member for preventing the further member from restricting movement of the restrictor mechanism with respect to one of the barrel and plunger shaft in said second direction until a predetermined point in an operation cycle of the syringe;
• wherein the first part and second part are moveable relative to each other over a limited range of movement to permit unlimited repeated movement of said plunger relative to the barrel in said first and second directions over said limited range.