As the years passed, there was a gradual shift in medical procedure from antisepsis (germ killing) to asepsis (germ-free practices). The very theory on which Lister based his entire system seemed to demand that aseptic methods replace antisepsis. But he opposed this change because he felt asepsis—which required the scrupulous sterilization of everything within the patient’s vicinity before procedures commenced—was impractical if surgeons were to continue operating outside the controlled environment of a hospital.
