Under the general term salts, or mineral matter, are included various combinations of lime, soda, potash, sulphur, phosphorus, magnesia, and iron, which are found principally in cereals, milk, meat, fish, and fruits. They are found in so minute quantities, that if, through ignorance or improper cooking, we are deprived of them, the system suffers from the want of them; and it is from the ill effects which follow that we judge their office to be a most important one. They replenish certain tissues, and are indispensable to the perfect building up of the body. More mineral matter is needed when the body is young; and it is especially important that children should not be deprived of it by being fed exclusively on arrowroot, sago, tapioca, etc., which are purely starch.

How much is needed we do not know; but the best development follows when the supply is from foods which are naturally rich in mineral matter, rather than from its addition to other foods.

Chloride of sodium, or common salt, seems to be essential to the proper digestion and absorption of food, and since there are many foods in which it is not found in sufficient quantity, it must be added to them. From habit, more is often used than the system requires; and when taken in excess it acts as an irritant, and sometimes occasions disease.

On the charts these mineral substances are classed as ash, because if the foods were burned there would be left a solid residue, resembling the ashes left in burning wood or coal.