6 fig6 illustrates the arrangement of pins 22 in the first leg 28 of slot 24 formed in tubular guard 6 in this view the second leg 32 of the slot 24 is illustrated as terminating in a position of 90 degrees to the initial position of slot 28 pins 22 are mounted in the body 8 of syringe 2 thus providing a positive guide for the travel of the guard as it is retracted and deployed fig7 through 11 illustrate the use of the guard during the typical medical use of a syringe fig7 illustrates the tubular guard 6 in its initial undeployed position showing that detent 26 prevents initial movement of tubular guard 6 unless enough force is exerted to overcome both the action of spring 16 against shoulder 20 and the force required to move pin 22 past detent 26 into the first portion of slot 28 also illustrated is a means of torsionally retaining spring 16 against shoulder 20 in this embodiment spring 16 has a portion 44 that is bent parallel with the axis of the spring and engages a notch 46 in shoulder 20 spring 16 can be installed with a torsional preload that forces the guard to rotate in the direction of slot 32 thereby assuring that the guard will latch in its safe position after use fig8 further illustrates the arrangement of spring 16 acting against both shoulder 20 on tubular guard 6 and shoulder 18 on syringe 2 prior to either the movement of tubular guard 6 or the depression of plunger 30 fig9 illustrates the initial stage of use of the syringe and guard showing that pin 22 has now moved past detent 26 and down the first leg 28 of v shaped slot 24 spring 16.