In the retrospect from the vantage ground of half a century of sanitary progress we recognize that during the third quarter of the last century the people of England were waging a successful war on domestic uncleanliness as a contributory, if not the sole cause of epidemic diseases. The health officer of England insisted that domestic filth was the actual cause of many of the low forms of disease, and named them accordingly, “filth diseases.” This official act of the highest health authority of that country led to the practice of cleanliness in the home and its surroundings. Filth in every form was removed as the necessary remedial measure against these diseases, with the result that not only were foreign pestilences prevented, but the whole brood of domestic diseases was greatly reduced in number, and the severity of cases that did occur was greatly diminished in virulence. But during the fourth quarter of the last century the question arose among scientists, “Why is filth--that is, decomposing matter--the prolific cause of disease?” The answer came from the famous Pasteur of Paris, and Lister of Edinburgh. “Filth is dangerous, because it is filled with germ life. The mere removal of filth from one locality to another does not render it harmless, except to those who are no longer in personal contact with it.” So-called filth was indeed harmless if the germs it contained were killed. [Sidenote: The Scheme of Sanitation Changed] The whole scheme of sanitation was at once changed: agents that would kill germs were eagerly sought by many scientists, and germicides were found in abundance. Cremation was most effectful, and was available in the destruction of masses of filth; but there was a phase of the question that required other methods. Lister announced that these disease-producing germs entered wounds and prevented healing, and that a germicide was required which would kill the germ in the wound and would not injure the living, healthy tissue. Further investigations showed that these dangerous germs were not confined to dust heaps, but existed in the unclean recesses of the human body. Sternberg startled the world with the announcement that an unclean human mouth contained germs of the most poisonous character. An eminent German surgeon declared that germs of a dangerous character existed in the folds of the skin of the palms of the hand which no amount of washing with soap and water could remove, and could be destroyed only by some agent directly applied. Sanitation of the body as well as of the dust heap now became the paramount question and especially did this apply to the practice of surgery. [Sidenote: The Mystery of Infection]