The universal custom of eating common salt with food testifies to a need of the body for this particular material. Such, indeed, is the fact. Chloride of sodium, or common salt, is found in all the tissues and fluids of the body. Without it the blood could not maintain its fluidity, nor could fluids pass through animal membranes. When it is remembered that it is only by the passage of fluids through the membranes of the blood vessels and the lacteals that the products of digestion can be absorbed, it will be seen how important it is to take salt with our food; in fact, if we were entirely deprived of common salt, we should soon die. In parts of Central Africa, where no salt is imported, and the local supply is small, salt is so highly prized that it is a valuable article for barter, taking the place of money. The salts of sodium potassium and magnesium are contained in small quantities in the animal and vegetable foods we take, and are important for the maintenance of the body in health. The salt which is, however, present in the largest amount in the body is lime, in the form of phosphate of calcium, which constitutes one-half of our bones. As the bones when once completely formed, at the age of about twenty-five, do not change in form, the presence of lime in the food is not of so much importance in adult life as in youth; in fact, it becomes often rather important to exclude it, for drinking water highly charged with lime salts may give rise to concretions and deposits in the kidneys and bladder. In such water the lime can be precipitated by boiling.

Fruit Salts

There are a whole class of salts called lactates, tartrates, citrates, malates, and acetates, which are present chiefly in fruits and vegetables. These are converted into carbonates in the body, and they contribute to keep the fluids of the body alkaline, which is necessary so that the functional activity of the body may be carried on. If these salts are not provided in the food, the body is ill nourished, and finally that condition of mal-nutrition known as scurvy is produced. Though green vegetables have small nutritive value, they always form part of the diet, owing to the fact that they furnish the body with the necessary fruit salts. The experience of sailors and Arctic explorers has taught us, often by the severe lesson of terrible suffering, that it is far better to do without the rum ration than without the preserved vegetables, which contain the fruit salts required.

Condiments, such as pepper, spices, and vinegar, give a flavour to food, and perhaps aid digestion by stimulating appetite.