A surgical stapling instrument has upper and lower elongate jaws for receiving a staple cartridge and an anvil respectively. A pusher bar and knife assembly including a pair of pusher bars and a central knife carrier moves longitudinally relative to the jaws to eject staples sequentially from the magazine...http://www.google.ca/patents/US4429695?utm_source=gb-gplus-sharePatent US4429695 - Surgical instruments
