Paré changed ideas about surgery. Before Paré, wounds were treated by pouring boiling oil into them. To stop the bleeding they were cauterized, ie sealed with a red-hot iron.
Paré began his career as an apprentice to his brother, a barber surgeon. In 1536, he became a surgeon in the French army, where he worked for 20 years. During this time he developed his ideas about surgery.
During one battle, supplies of cautery oil ran out. Instead, Paré used an ointment of egg yolk, oil of roses and turpentine which had been used in Roman times. He found that the wounds treated with this mixture healed better than those treated with boiling oil.
During amputations, instead of cauterizing, he used ligatures, ie silk threads to tie blood vessels. Unfortunately, ligatures did not reduce the death rate. Dirty surgeons' hands and contaminated ligatures caused infections in the wounds being treated.
In 1575, he published his book The Collected Works of Ambroise Paré (Les Oeuvres d'Ambroise Paré) which proposed changes to the way surgeons treated wounds and amputations.