THE study of iodine metabolism has been retarded by the technical difficulty of estimating accurately the small amounts of iodine which occur in foodstuffs and in tissues and body fluids. Kendall's method [1914, 1920], which is that most widely used at the present time, is admirably suited for the analysis of thyroid tissue, which contains roughly from 0-01 g. % to 0 5 g. % of iodine, and, as modified by Kelly and Husband [1924], it is in routine use at this Institute for that purpose. The method has, however, a lower limit of detectable iodine of 5y (y = 0-000001 g.). For the estimation of iodine in human blood, therefore, Kendall required 100 cc., since the content is only 13 y %. The method is

THE metabolism of calcium and phosphorus is intimately involved in the action of ultra-violet irradiation. Hess and Lundagen [1922] have shown that in infants there is a seasonal tide of blood phosphate depending on the seasonal variation in sunlight. The increased deposition of calcium and phosphorus in bone as a result of irradiation, whether natural or artificial, has been amply proved by such work as that of McCollum and others [Powers, Park, Shipley, McCollum and Simmonds, 1921]; and numerous experiments have been carried out in investigating the effect of ultra-violet light on growth and the prevention of xerophthalmia.In most of the above instances, however, the changes in calcium and phosphorus metabolism have been deduced from a final chemical analysis of the tissues, or from histological examination. In only very few cases has a complete calcium and phosphorus balance bean followed out.The present work was accordingly undertaken with the object of obtaining a quantitative estimate of the retention of these minerals under the influence of light over a fairly long period. Previous work, for the greater part, where it has not been on the human subject, has been carried out on small animals. For the present investigation the pig was selected for the following reasons:(1) The growing pig of about three months old retains large amounts of calcium and phosphorus-roughly about 5 g. of CaO and of P205 per diem .(2) A considerable amount of data on the retention of these minerals by the pig has already been accumulated at this Institute and serves as a guide.(3) In the pig there is no thick coat to interfere with irradiation of the skin.The importance of the proportions in which inorganic constituents are present in the diet has been shown by Elliot, Crichton and Orr in their work on rickets in pigs [1922]. In the case of the rat, Hess, Unger and Pappenheimer [1922] find that the rickets-producing effect of a diet adequate in calcium but low in phosphorus may be prevented by short exposures to direct sunlight. In the present investigation the calcium and phosphorus retention was accordingly determined in irradiated pigs which were on diets ill-balanced and

DURING the past few years a considerable amount of work has been done on the mineral metabolism of lactating aniimials. A review of the recent literature is given by Meigs [1922]. It has been found that, during a large part of the period of lactation, the

No abstract

In the two preceding communications we have discussed the calcium balances and weight increase of natives, both adult and growing, on certain institution diets, with and without additions.Various considerations pointed to a relative or absolute deficiency of calcium in the above diets. The experimental additions made, therefore, were (1) a mineral mixture reproducing closely the ash of cows' milk; (2) cod-liver oil; (3) cod-liver oil plus the mineral mixture; (4) olive oil plus KI; (5) milk.