Medically a poison can be any substance applied to the body, ingested or developed within the body, which causes or may cause disease. The word poison was first recorded in Middle English in a work composed around 1200. A poison is any substance which, when introduced into or absorbed by a living organism, destroys life or injures health. Poison is defined as any substance capable of producing a morbid, noxious or deadly effect. A poison is a material that inhibits other substances, especially enzymes, and the vital biochemical processes they are involved in. Enzymes are crucial because every chemical change that takes place to repair tissue or to assimilate food involves the activity of enzymes. Without enzyme activity there is no biological activity, no life.