The sanitary revolution involved much more than sewerage systems and clean water. Discovery of the tubercle bacillus and other dangerous respiratory pathogens led to understanding of the way infected sputum spread respiratory infection. People became fastidious about covering their nose and mouth when they coughed or sneezed -- instead of clearing their nostrils on the table cloth, and coughing and spitting on the living room floor. Doctors and nurses began to wash their hands after Oliver Wendell Holmes[7] and Ignaz Semmelweiss[8] demonstrated how childbed fever was spread by dirty hands from sick to healthy women; and the custom of personal hygiene spread to the rest of society. It was comparable to, and as important in altering the pattern of disease, as the sense of values and the behaviour change in much of the western world since the discovery by Doll, Hill[9], and others in the 1950s, that cigarette smoking causes lung cancer, and greatly increases the risk of coronary heart disease.