Abstract: A self-contained predetermined dosage hypodermic ampule with enclosed sterile needle projected by a companion injector device from the sealed forward end of the ampule, with liquid medicament pressurizing means for dispensing the medicament from the needle and into the tissue of the patient during penetration of the tissue by the needle, all portions of the length of the needle being hygienically sealed from external contamination at all times; the companion injector means having simply operated and dependable safeguards against accidental operation, and the injector means and hypodermic needle cooperating to insure smooth, non-sticking operation of the medicament pressurizing means.