A properly balanced diet should contain sufficient calories and inorganic salts, especially iron, phosphorus, calcium and iodin. There should be a sufficient variety of foods to provide the necessary vitamins. It is also thought that a certain amount of roughage is necessary. If we expect the best results from our digestive tract we should strive to keep the balance approximately the same each day. This is not because Innate Intelligence is unable to adapt the body to a great variety of food, but it is more to prevent a necessity for such extreme adaptation. To illustrate: If we constantly introduce too much acid into the stomach, it necessitates an adaptative action on the part of Innate Intelligence in the production of an alkali to neutralize the acid. Since we know so little educationally about nutrition, it is wise for us to eat as great a variety of foods as possible, and especially is this necessary in providing a balanced ration for growing children. In considering food we must not forget the importance of proper digestion and assimilation. In Chiropractic the diet is of little importance, providing the functional activities of the body are maintained at normality. CLASSIFICATION OF FOODS Sources of Food Foods are classified according to source, chemical composition, physical properties and function. In classifying food as to its source we have three classifications: animal, plant and mineral. Meat, fowl, fish, shell-fish, eggs, milk and its products, animal fat and gelatin help to constitute the animal foods. Seeds, roots, leaves, cereals, vegetables, fruits, sugar and vegetable oils are plant foods. From the mineral there are: iron, potassium, phosphorus, iodin, sulphur. These are obtained from the animal and plant foods. Water is not classed as a food, but it enters into the diet as a very important constituent. Chemical Composition From the standpoint of chemical composition foods are grouped into two classes, nitrogenous and non-nitrogenous. Both the animal and vegetable kingdom contribute foods to each of these classes, although the animal substances belong more to the nitrogenous, while the vegetable kingdom belongs more particularly to the non-nitrogenous foods. The nitrogenous foods consist chiefly of carbon, oxygen, hydrogen and nitrogen and are considered to be essentially tissue builders. Hygienists speak of the non-nitrogenous foods as being force producers, asserting that these foods supply energy for muscular action. Physical Properties Under this heading foods are classified as: (a) solids, semi-solids and liquid foods; (b) fibrous, gelatinous, starchy, oleaginous, crystalline and albuminous foods. The indigestible residue is called roughage. Function Foods are classified as: Proteins, carbohydrates, fats, condiments, inorganic salts and vitamins.