bladder, and even in certain cases will tend to disintegrate it by solution of some of its elements, and thus to favor its crumbling and expulsion. This is a principle which must never be lost sight of in the treatment of calculi. The immersion of the stone in a liquid of a lower specific gravity than that in which it has formed and grown tends to dissolve out the more soluble of its component parts, and thus to destroy its density and cohesion at all points, and thereby to favor its complete disintegration and expulsion. This explains why cattle taken from a herd on magnesian limestone in spring, after the long, dry feeding of winter, usually have renal calculi, while cattle from the same herd in the fall, after a summer's run on a succulent pasture, are almost always free from concretions. The abundance of liquid taken in the green feed and expelled through the kidneys and the low density or watery nature of the urine have so opened the texture and destroyed the density of the smaller stones and gravel that they have all been disintegrated and removed. This, too, is the main reason why benefit is derived from a prolonged stay at mineral springs by the human victims of gravel. If they had swallowed the same number of quarts of pure water at home and distributed it at suitable times each day, they would have benefited largely without a visit to the springs. It follows from what has been just said that a succulent diet, including a large quantity of water (gruels, sloppy mashes, turnips, beets, potatoes, apples, pumpkins, ensilage, succulent grasses), is an important factor in the relief of the milder forms of stone and gravel.