A surgical stapling instrument is disclosed, having upper and lower elongate jaws, one of which is adapted to receive a staple magazine, the other jaw being adapted to receive an anvil or to serve as one itself. A pusher bar and knife assembly including a pair of pusher bars and a central knife carrier...http://www.google.co.uk/patents/US4520817?utm_source=gb-gplus-sharePatent US4520817 - Surgical instruments
