A syringe includes a barrel having a mouth on one end portion, a needle having a nipple engaged in the mouth of the barrel, a plunger slidably engaged into the barrel, a piston releasably attached to the plunger and having a protrusion for engaging with a needle mounting, and a follower slidably engaged in the plunger and having a catch device for securing the piston to the follower, and a spring biasing member engaged with the follower for biasing and retracting the follower and the piston and the needle mounting and the needle into the barrel when the latch member of the latch device is disengaged from the needle mounting and for preventing the needle from being exposed after use.
