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.

Sulphur is present in protein and we get a sufficient supply from milk, meat and legumes. The element sulphur is quite inert and harmless, but some of its acids and salts are very poisonous. Sulphur dioxide is freely used in the process of drying fruits, as a bleacher. In this form it is poisonous, and for that reason it would be well to avoid bleached dried fruits. We need some sulphur, but not in the form of sulphur dioxide or concentrated sulphurous acid, both of which are used in the manufacture of food.

Sodium, in its elementary state, which is not found in nature, is a white, silvery metal. It is found in great abundance in the succulent vegetables, and is present in practically all foods. As sodium chloride, or common table salt, it is taken in great quantities by most people. Those who have no salt get along well without it, which shows that it is not needed in large amounts. If but a little is added to the food, it does no perceptible harm, but when sprinkled on everything that is eaten, from watermelons to meat, it is without doubt harmful. By soaking foods, they are deprived of much of their soda: The two sodium salts that are very abundant are sodium chloride, or common salt, and sodium carbonate, generally called soda.

Chlorine is ordinarily combined in our foods with sodium or potash, forming the chlorides. It is essential to life. He who gets enough sodium also gets enough chlorine. In its elementary form it is an irritating gas, used for bleaching purposes.

Fluorine is present in small quantities in the body, appearing as fluorides in the bones and teeth. It is supplied by the various foods. In its elementary form it is a poisonous gas.

Potassium is found in the body in very small quantities, but it is very important. It is mostly in the form of potassium phosphate in the muscles and in the blood. It is necessary for muscular activity. It is found in most foods in greater abundance than is sodium, which indicates that it plays an important part in development. Like sodium, it is easily dissolved out of foods which are soaked in water, and this is one of the reasons that vegetables should not be soaked and the water thrown away. It is very peculiar in its metallic state, being a silvery metal, very light in weight, which burns when thrown upon water. That is, it decomposes both itself and the water with the liberation of so much heat that it fires the escaping hydrogen, which burns with a violet flame. Pure potassium is not found in nature.

Iron is found in very small quantities in the human body, but it is absolutely essential to life. Animals deprived of iron die in a few weeks, and people will do the same under similar circumstances. Iron is obtained principally from fruits and vegetables, but it is also present in other foods. Man can not make use of inorganic iron. He has to get his supply from the vegetable and animal kingdoms. The giving of inorganic iron is folly and helps to ruin the teeth and the stomach of the one who takes it. In the form of hemoglobin this element is the chief agent in carrying oxygen from the lungs to the tissues of the body. In the manufacture of foods, much of the iron is lost. For instance, whole wheat flour contains about ten times as much iron as does the white flour. Too little iron causes, among other ills, anemia, and if the iron is very low, chlorosis or the green sickness may ensue.