Calcareous deposits, especially local, are of frequent occurrence in degenerated and necrotic tissue, old inflammatory exudates, and other dead material such as thrombi. Calcification in the media and intima of the arteries in old persons, in pleural and pericardial exudates where large calcareous plates may form, the concretions in the apices of the lungs and in the bronchial lymph nodes as the result of tuberculosis, are all familiar examples. Wherever tissue degenerates, deposits of calcium salts may take place, usually in the stroma, but also, although rarely, in the cells themselves, as, for instance, in the renal epithelium in toxic necrosis, in ganglion cells, in muscle fibers. Deposition of calcium salts also occurs on a larger scale, when it may give rise to peculiar conditions and even distinct diseases. The cause of such deposits is in general assumed to be a supersaturation, so to speak, of the blood and tissue