Instances of the deposition in the tissues of other than calcareous salts are abundantly met with in gout. In this disease cartilage, ligaments, and tendons, bone-marrow, muscle, the endocardium and aorta, the membranes of the brain and spinal cord, the skin and kidneys, may contain deposits of acicular crystals and amorphous granules. Although these deposits are largely composed of sodium urate, calcium urate may be present with other salts, as sodium chloride and calcareous compounds. According to Ebstein,[38] the earthy salts in gout are deposited in necrotic patches of previously diseased tissue. The local conditions are therefore analogous to those concerned in the formation of chalky concretions. [Footnote 38: _Die Natur und Behandlung der Gicht_, Wiesbaden, 1882, 45.] Concretions and calculi are collections of earthy salts, the former lying within tissues, the latter being present in canals opening externally. Both represent the results of a deposition in and upon organic material, which is often an inflammatory product, at times surrounding a foreign body acting as the exciting cause of the inflammation. The earthy matter of which the concretion is composed consists mainly of carbonate and phosphate of calcium, while the chemical properties of the calculi often vary in accordance with the nature of the secretion which flows by them. The salivary, pancreatic, intestinal, lachrymal, and prostatic calculi are chiefly formed of calcareous salts. These salts also are an important, if not the chief, constituent of biliary and urinary calculi. In the former pigment, bile acids, and cholesterin may also be present. Urinary calculi are of still more varied composition, containing not only the calcium salts, as the oxalate, phosphate, and carbonate, but also uric acid and the urates of sodium and ammonium, in addition to the ammoniaco-magnesian phosphate. The infiltration with calcium salts may prove beneficial as well as {90} injurious--beneficial under those circumstances where further changes might prove harmful, as in the softening of cheesy material or the maceration of a dead foetus in the abdominal cavity. The calcification of certain tumors, as the fibro-myoma of the uterus, is equally sanatory, the further growth of the calcified parts being thus checked. The calcification of an aneurismal sac may prove beneficial in strengthening a weakened blood-vessel. The injurious effects are seen more particularly in case of the calcareous infiltration of the middle coat of arteries. Such vessels become converted into rigid and unyielding tubes at various parts of their course, and the nutrition of peripheral parts becomes correspondingly lessened. Hence, in great measure, the liability of old people to serious inflammatory processes from trivial irritation of peripheral portions of the body, such inflammations often terminating in gangrene.