Carbolic acid is used by Dr. Parsons (actor Ed Nelson) to sterilize the operating room and prevent infection. The medical use of carbolic acid (phenol) for sterile, antiseptic surgery had been perfected in the late 1860's by British Surgeon Joseph Lister. By the 1870's (the time setting of "The Tall Man"), the use of carbolic acid by doctors and surgeons was becoming common and accepted.