Lusk also emphasizes the importance of a diet rich in calcium for pregnant women, especially during the last ten weeks of pregnancy, when the fetus is storing calcium at a rapid rate. He cites * the data of Hoffstrom,† who computed in considerable detail the demands of the fetus upon the mother for nitrogen, phosphorus, calcium, and magnesium at different stages of intrauterine life.

Strong confirmation of this has recently been obtained from investigation of farm animals. The experiments of Steenbock and Hart show that the production of milk in cows and goats causes a heavy drain upon the calcium of the skeleton unless the amount of calcium contained in the food be very abundant. They also point out that the mammary glands likewise make large demands upon the phosphorus supply and suggest that if the food be not rich in phosphorus the destruction of bone tissue to furnish phosphorus for milk production may result in still further loss of calcium from the body.

Forbes and Beegle in studying the mineral metabolism of the milch cow found a heavy loss of body calcium, notwithstanding the fact that the food was believed to supply liberal amounts of all essential elements and was eaten in sufficient quantity to induce storage of nitrogen. That calcium may be lost from the body while nitrogen is being stored has also been emphasized by several other investigators (Steenbock and Hart, Weiser, and others). According to Forbes it may be necessary to continue high calcium feeding for some time after the cessation of lactation, in order to replace the calcium which the maternal organism has lost.

In children after weaning and throughout early childhood there are apt to be frequent disturbances of the absorption and metabolism of calcium, in some cases due to distinct disorders of digestion, in other cases to more obscure irregularities in nutrition. In order that these fluctuations shall not interfere with the steady growth of the child, it is obvious that the food must furnish a fairly liberal surplus of calcium. Even under the most favorable conditions, a rapidly growing child will presumably need more bone-making material in proportion to its total food than do adults, who alone have served as subjects for the metabolism experiments upon which our present estimate of calcium requirement is based. Camerer, in summarizing a long series of investigations upon the food requirements of children at different ages, concluded that the amount of calcium received by the average nursling is just about sufficient to maintain a normal rate of growth, leaving little if any "margin of safety"; and Bunge, from a comparison of the calcium contents of different staple foods, points out that calcium more than any other inorganic element is likely to be deficient as the result of the change of diet from mother's milk to other forms of food.

* Lusk. Science of Nutrition, 3d edition, pages 389-390.

† Hoffstrom. Skandinavisches Archiv fur Physiologic, Vol. 23, page 326 (1910).

Herter* estimates that in order to support normal growth of the skeleton there must be an average storage of about 37 grams of calcium (51.6 grams of calcium oxide) annually throughout the period from the third to the sixteenth year. This means an average daily storage of somewhat more than 0.10 gram of calcium during this thirteen-year period. In order to accom-plish such a storage it is plain that the daily food of the child must contain a surplus of more than 0.10 gram of calcium per day beyond the amount required for maintenance, which latter amount should provide for the frequent failures of complete utilization which have already been mentioned.

Herbst † studied the calcium metabolism of 6 boys between the ages of 6 and 14 years and found that they were storing from 0.010 to 0.016 gram of calcium per kilogram per day, or 0.21 to 0.39 gram per capita per day. If normal growth of boys of these ages involves such a large storage of calcium, it is plain that the food of such boys must be rich in calcium if they are to develop advantageously. These boys consumed about 3 to 4 times as much calcium in proportion to their weight as is required for the maintenance of men.

* Infantilism.

† Jahrh. Kindcrheilkunde, Vol. 76. Ergdnzungsheft, pages 40-130.

From such considerations as these it is evident that one should be very liberal in calculating the amount of calcium to be supplied to growing children.

If 0.45 gram is the minimum on which an average man can maintain equilibrium, it would seem that the food of a family should furnish at least 0.67 gram * of calcium or 0.9 to 1.0 gram of calcium oxide per man per day. This is less than is advo-cated by such recent writers as Albu and Neuberg, Gautier, Obendoerffer, and Emmerich and Loew, or reported by Nelson and Williams; yet about 50 per cent of the American dietaries which have so far been studied with respect to their ash constituents show less than 0.67 gram of calcium per man per day, and about 15 per cent of them show less than 0.45 gram calcium (0.63 gram CaO) per man per day. In some cases the deficiency in calcium is incidental to a general deficiency in the amount of food; but if the food consumed in each dietary had been increased or decreased to just 3000 Calories there would have been less than 0.67 gram of calcium in 46 per cent, and less than 0.45 gram in 8 per cent of the cases. Since inorganic forms of calcium are utilized in nutrition, the lime of the drinking water may be added to that of the food in calculating the amount consumed, and to this extent the actual nutritive supply may be greater than the dietary studies show, but unless a very "hard" water be used for drinking, it is unlikely that the lime from this source will cover more than a small part of the calcium requirement. It is probable too that losses of food calcium in cooking may fully offset the calcium obtained from the drinking water. Apparently theAmerican dietary is more often deficient in calcium than in any other element; certainly more attention should be paid to the choice of such foods as will increase the calcium content of the dietary. The use of more milk and vegetables with less meat and sugar will accomplish this and usually improve the diet in other directions as well.

* This amounts to setting a tentative "standard" 50 per cent higher than the average minimum, as in the cases, of protein and of phosphorus.