Xcviii. the Calcification in Vitro of Kidney, Lung and Aorta. by Adele Helen

ALTHOUGH calcification in the animal body is normaly confined to hypertrophic cartilage and osteoid, in certain abnormal or pathological conditions deposits of calcium salts may also be formed in other tissues, among which are the kidney, the lung and the arteries. Some of these conditions, for example hypervitaminosis D, are associated with exceptionally high concentrations of bloodcalcium or phosphate, suggesting that the plasma has become by some agency supersaturated with calcium salts. In others degenerative changes in the tissues themselves precede, and may possibly be the primary cause of, calcification. Without attempting to reproduce in vitro all the abnormal conditions concerned it seemed of importance to discover whether the calcification of such tissues could be induced in our experimental solutions, and if so, in what respects the process would differ from that taking place in hypertrophic cartilage and osteoid. Experiments of this kind, though carried out with the tissues of normal animals, might yet throw light on abnormal calcification and, by differentiation, on the normal process of calcification in the skeleton. Two questions of particular interest were: (a) whether the phosphatase which occurs in some of these tissues is at all responsible for their calcification, and (b) whether these tissues possess in any degree properties akin to those which constitute the second mechanism of cartilage.