_Carbon_ is the chief producer of energy within the body, being the principal constituent of starches, sugars and fats. It is what we rely on for internal heat, as well as for heating our dwellings, for the essential part of coal is carbon. The carbonaceous substances are needed in greater quantity than any other, but if they are taken pure, they cause starvation more quickly than if no food were eaten. This has been proved through experiments in feeding nothing but refined sugar, which is practically pure carbon. Salts and nitrogenous foods are essential to life. _Hydrogen_ is a very light gas, without odor, taste or color. It is a necessary constituent of all growing, living things. It is plentifully supplied in water. All acids contain hydrogen and so does the protoplasm of the body. _Nitrogen_ is also a colorless, tasteless, odorless gas. It is an essential constituent of the body, being present in all compounds of protein. It is abundant in the atmospheric air, from which it is taken by plants. We get our supply either directly from vegetable foods or from animal products, such as milk, eggs and meat. _Calcium_ is needed principally for the bones and for the teeth, but it is also necessary in the blood, where it assists in coagulation. We get sufficient calcium salts in fruits, grains and vegetables, provided they are properly prepared. The conventional preparation of the food often results in the loss of the various salts, which causes tissue degeneration. If the supply of calcium in the food is too small, the bones and the teeth suffer, for the blood removes the calcium from these structures. Growing children need more calcium proportionately than do adults. This is without doubt the reason pregnant women suffer so much from softening of the teeth. They are fed on foods robbed of their calcium, such as white bread and vegetables that have been drained. _Phosphorus_ in some forms is a poison whether taken in solid compounds or inhaled in fumes, producing phossy jaw. In other forms it is indispensable for bodily development. The compounds of phosphorus are present in fats, bones and protein. In natural foods they are abundantly present, but when these foods are unduly refined, or are soaked in water which is thrown away, much of the phosphorus is lost. We get phosphorus from milk, eggs, cereals, legumes and other foods. Of course, there is phosphorus in fish, but those who eat sea food to make themselves brainy will probably be disappointed. Phosphates are necessary for brain development, but those who eat natural foods never need to go to the trouble of taking special foods for the brain. If the rest of the body is well nourished, the brain will have sufficient food, and if the body is poorly nourished the brain will suffer.