Non-reusable syringe for medical purposes

A syringe for medical use comprising a watertight cylindrical body, a plunger movable linearly inside the body, a needle carrier also movable linearly inside the body and relatively to the plunger, a needle carried by the needle carrier, wherein before the syringe is used, the needle is located for protection inside the watertight cylindrical body;

• and elastomeric plug which can be perforated by the needle and that closes a distal end of the syringe;
• first snap on coupling means engageable between the needle carrier and the distal end of the syringe upon movement of the plunger to a first position in which the plunger has advanced the needle carrier and needle to a position in which the first snap on coupling means is engaged and the needle has penetrated said plug and is extended to a position of use, second snap on coupling means non-releasably engageable between the plunger and the needle upon movement of the plunger to a second position beyond said first position in the direction of said advance of the needle, and a member within the syringe which has lesser resistance to compression when wet than when dry and which when dry limits movement of the plunger to said first position and which when wet permits movement of the plunger to said second position.