The part played by habit in matters of health is often overlooked. Although the body adjusts itself to widely varying conditions and even to unfavorable ones, the importance of forming desirable habits cannot be overemphasized. Sudden or radical changes in living, however, particularly among people no longer young, may play havoc. New and violent systems of exercise, weight reduction, and food fads forced on families by enthusiastic discoverers involve considerable risk. Many elements enter into health; in no single one is found hygienic salvation. Temptation always exists to emphasize one element at the expense of others. For instance, people who insist upon overventilating rooms regardless of others' comfort may themselves be utterly careless in regard to necessary sleep, and more than one fastidiously clean person has disregarded the highly unclean condition of constipation. To maintain sound health only a rational program will suffice: properly balanced work and play, sleep and food and all other elements must be included in due proportion. And over-anxious health seekers might well remember that health is not so much an end in itself, as a means to a happy and productive life; even in concern over health, it is possible for him that saveth his life to lose it. EXERCISES 1. Explain the difference between an hereditary disease and hereditary susceptibility to a disease. How may hereditary susceptibility to a disease be combatted? 2. What are the essentials of good ventilation? 3. What is the proper temperature for a living room? What are the effects of higher temperatures? Of lower temperatures? 4. Describe methods for maintaining household cleanliness. 5. Discuss the importance from the point of view of health, of dust; of insects; of garbage; of sewage. 6. What principles should guide one in deciding whether a certain water supply is safe to use for drinking purposes? What are the dangers of impure water? How can impure water be rendered safe? 7. What diseases may be carried by milk? How can milk be rendered safe? 8. Explain the health aspects of personal cleanliness. 9. What care should be given the teeth and mouth? Why? 10. What bad results frequently follow constipation? How should constipation be remedied? 11. Name seven factors that are important in causing fatigue. Why is it uneconomical to continue work, either physical or mental, beyond the point of fatigue? 12. What facilities for recreation, especially in the open air, does your community provide for little children? For school children? For working boys and girls? For grown people? FOR FURTHER READING Health and Disease--Roger I. Lee, Introduction and Chapters I, III-V, VII-IX. How to Live--Fisher and Fisk, Chapters I, III-V. The Human Mechanism--Hough and Sedgwick, Chapters V, XXII-XXIX. Disease and Its Causes--Councilman, Chapters X, XII. Fatigue and Efficiency--Goldmark, Chapters II, III. Preventive Medicine and Hygiene--Rosenau.