Water is rendered quite harmless by boiling. In cases where it is not possible to have a pure water supply, where the water can only be obtained from a polluted river or well, cases which are common enough in the country districts in England, and almost invariable abroad, it is more than advisable, it is necessary, for the preservation of health, to boil all the water used for drinking purposes. A most useful, and, in fact, an indispensable addition to the traveller's luggage when going abroad is a little Etna and a spirit lamp. The purchase of a few lemons will then enable the traveller to make a refreshing and inexpensive beverage with water taken from the bedroom carafe and thoroughly boiled. If he follows this simple plan of drinking fresh lemonade made with well boiled water, he will escape the risk of imbibing the germs of typhoid fever or cholera. Boil your water is the sum and end of all the teachings of the bacteriologists and sanitarians as a protection against typhoid and cholera and infectious diseases carried by water.

The amount of water daily required to be taken varies considerably with the individual, some persons losing more by perspiration and the kidneys than others. From 2½ to 4 pints a day is the usual quantity required, and with most persons much of this is taken in the form of tea, coffee, or beer. A draught of fluid is useful after dinner to wash any undigested particles out of the stomach.