The proportions of water are not always quite the same, nor does the identical water present in any part of the body at any given moment remain there. There is a constant movement, a continual renewal going on in the body, and water helps to accomplish this renewal. By means of the watery substances, the saliva, the bile, and other juices of the stomach and intestines, the solid nutritive parts of the food are dissolved, and pass into the blood to renew the waste, and to keep up that continual current called life. Water is also useful in carrying off the worn out and useless materials which pass out through the fluid excretions and through the vapors from the lungs and skin. =Water in Food.=--The amount of water contained in many articles of food that appear quite solid is generally surprising to those unacquainted with the chemistry of foods. In one hundred pounds by weight, fresh oatmeal contains 5 pounds of water. Corn and barley meal, wheat flour, peas, and beans contain 14 pounds; rice 15; bread 40; potatoes 75; grapes 80; parsnips 81; beets 82; apples 83; carrots and cabbages 89; onions 91; lettuce 96. Of the animal foods, butter contains 10 pounds of water in one hundred; bacon 22; cheese 34; eggs 72; lean meat 73; fish 74; milk 86. By cooking, most foods lose a part of their natural moisture. The eatable part of a mutton chop contains 70 per cent of water before cooking, and 54 per cent after. =Daily Requirement.=--Scientific sanitarians have estimated the daily requirement of water for a person at from twelve to sixteen gallons. The British War Department aims to provide each soldier with fifteen gallons daily. In cities the daily allowance per capita is fifty gallons and upwards, which provides for animals, manufacturing purposes, fires, sewerage, etc., as well as for drinking, cooking, bathing, and other wants of man. =Sources of Supply.=--The importance of an abundant supply of pure water is becoming more and more apparent each year. The numerous and serious epidemics throughout the country whose sources have been traced to the use of impure water leave no room for question on this point. Most cities draw their supplies from rivers and lakes. If these sources are kept free from sewage and the waste of manufacturing establishments the water is likely to be pure and wholesome. Subsiding reservoirs and filtration beds are needed to take out the mud occasioned by rains, and to catch up whatever floating matter may be carried into the basins. Muddiness is not always an indication of unwholesomeness, nor is clearness a proof of purity. Germs of disease have been found in the clearest water. Whenever there is the least suspicion of unwholesomeness, all water used for cooking and drinking should be boiled. It is not safe to trust to the theory, held by some, that a running stream, even if polluted, will in flowing a distance of twelve or fifteen miles purify itself.