Dr. Lister was contemporary to French chemist Louis Pasteur, who pioneered the theory that infectious diseases were caused by germs—which could be neutralized if heated to high temperatures. While Pasteur was studying germ theory and investigating what would come to be known as pasteurization, Dr. Lister was investigating the microscopic changes in tissue that lead to inflammation and infection. The application of Pasteur's theories to the operating theater led Dr. Lister on the path that would ultimately give way to antiseptic surgical techniques.
Because heat sterilization could not be applied directly to patients, Dr. Lister began looking for a chemical that could bring similar results. An article in a local newspaper raised his interest in crude carbolic acid—which was showing promising results in sewage treatment. People and animals near fields fertilized with treated sewage were showing fewer diseases. Dr. Lister began applying purified carbolic acid to wounds in 1865. He also led the charge in suggesting that surgeons wash their hands and sterilize their instruments before operating. Sterile catgut, silk for sutures and sterile gauze dressings are more of his legacies.