needle into the syringe barrel.FIG. 15 is an isometric view of a retractable syringe, the syringe being shown in exploded view with three types of caps and without the syringe cartridge as in FIGS. 2 and 10.FIG. 16 is a longitudinal cross-sectional view of the barrel of the retractable syringe of FIG. 15.FIG. 17 is an end view of the barrel of FIG. 16 taken along section lines 17--17 of FIG. 2.FI