The Waste Materials. By the time that the remains of the food-pulp have reached the middle of the large intestine, they have lost all their nutritive value and most of their water. All the way down from the upper part of the small intestine they have been receiving solid waste substances poured out by the glands of the intestines; indeed, the bulk of the feces is made up of these intestinal secretions, not, as is generally supposed, of the undigested remains of the food. Ninety-five per cent of our food is absorbed; the body-engine burns up its fuel very clean. The next largest part of the feces is bacteria, or germs; and the third and smallest, the indigestible fragments and remainders of food, such as vegetable fibres, bran, fruit skins, pits, seeds, etc. Hence the feces are not only worthless from a food point of view, but full of all sorts of possibilities for harm; and the principal interest of the body lies in getting rid of them as promptly and regularly as possible. It can easily be seen how important it is that a habit should be formed, which nothing should be allowed to break, of promptly and regularly getting rid of these waste materials. For most persons, once in twenty-four hours is normal; for some, twice or even three times in the day. Whatever interval is natural, it should be attended to, beginning at a fixed hour every morning. Constipation, and how to Prevent It. Constipation should not be treated by the all too common method of swallowing salts, which will cause a flood of watery matters to be poured through the food tube and sluice it clean of both poisons and melting food at the same time, leaving it in an exhausted and disturbed condition afterwards; nor by taking some irritating vegetable cathartic, generally in the form of pills, which sets up a violent action of the muscles of the food tube, driving its contents through at headlong speed; nor by washing out the lower two or three feet of the bowel with injections of water; although any or all of these may be resorted to occasionally for temporary relief. A very large portion of the food eaten is sucked out of the food tube into the blood vessels, passes through a large area of the body, and is poured out again as waste through the glands of the lining of the lower third of the bowel. Constipation, therefore, is caused by disturbances which interfere with these processes _all over the body_, not only in the stomach and bowels. Its only real and permanent cure is through exercise in the open air, sleep, and proper ventilation of bedrooms, with abundance of nourishing food, including plenty of green vegetables and fresh fruits.