Vaccination, cause of sore arms after, 140, 141; discovery of, 132; how, prevents smallpox, 135; necessity of repeating, 137; pretended vaccination, 138; when successful, 138 Ventilation, in homes, 46, 159; in public buildings, 48, 161; in workshops, 48 Veins, 171 Venous blood, 171, 172 Villi, 171 Vitreous humor, 178 Voluntary action, 181 Water, avoid polluting, 85-88, 115; effect of sewage on, 85, 115; how germs get into, 85-88; polluted, in milk, 27; safe sources of, 88 Wells, how polluted, 86, 87; relation of toilets to, 86, 87 Windows, should be kept open, 45-47; should be screened, 83 Wood-ticks, as disease carriers, 93; how abolished, 94 Wounds, importance of keeping clean, 97 Yards should be clean, 77 Yellow fever, how transmitted, 92; how prevented, 92 FOOTNOTES: [1] Bujar and Baier state that the nourishing power of bacon is represented by 2,767, while the nourishing power of butter is represented by 2,610. [2] The cleaning out of these cemented vaults is an exceedingly unpleasant task. Some prefer to have a strong, water-tight box placed under the closet seats. When this box is nearly full, it can be removed to some place where fertilizer is needed, and there emptied, the contents being plowed into the ground. In order to make this task as simple as possible, it is a good plan to put the box on skids, and have a heavy strip in one end with a bolt and ring through it, so that a horse can be hitched to the box to draw it away. If a little dry earth or lime is put into the box each day, there will be no unpleasant odor. [3] The teacher should demonstrate the action of acids and alkalies on a solution of litmus. [4] At the request of many practical teachers the author has appended this brief summary of anatomy. The material is intended to be used for reference or to be assigned as lessons in connection with the chapters of the book, at the discretion of the teacher. End of Project Gutenberg's Principles of Public Health, by Thos. D. Tuttle