Calcium is the most important of the inorganic elements in the animal body. In the adult1 it furnishes 2 per cent of the total weight, and 99 per cent of this amount is found in the bones and teeth. It is present in all tissues, including the blood, and without it life, as we know it, would be impossible. It is self evident, therefore, that a liberal supply of calcium in the diet must be a matter of vital importance at all times. There are, however, three periods during the life of the individual during which it is of particular importance. First, that of growth, when bulk is being added so rapidly to all the tissues; second, that of pregnancy, when the mother must supply the calcium for the bones of the developing fetus, and third, that of lactation, when the milk from the mother must act as a