Abstract: A novel syringe is provided herein. It includes a cylindrical barrel having a closed forward end provided with a longitudinally-extending channel therethrough. A hypodermic needle is slidably received in the channel. A frangible septum is disposed in the channel and is adapted to be pierced upon inward sliding movement of the hypodermic needle. At least a single stopper is slidably and sealingly disposed in the barrel to divide the barrel into (i) a forward, payload chamber, defined between the closed forward end of the barrel and the leading face of the stopper, and (ii) a rearward propulsion chamber downstream of the trailing face of the stopper. The propulsion chamber is controllably variably prechargeable to a predetermined gaseous pressure. The syringe may be used with a novel retractable collar and with a novel sliding fin assembly.