These forcible housecleanings of Nature are colds, catarrh, skin eruptions, diarrheas, boils, ulcers, abnormal perspiration, hemorrhages and many other forms of inflammatory febrile diseases. Sulphur and mercury may drive back the skin eruptions, antipyretics and antiseptics may suppress fever and catarrh.
Here the critical problem is where to draw the line. Perhaps the best general answer is to measure productiveness, including those who make a net contribution, including those whose presence is desirable and excluding undesirables. Again this involves periodic housecleanings.