Medicine, the disease of the stone in the bladder or kidneys. The term is Latin, and signifies a little pebble. The calculus in the bladder is called lithiasis; and in the kidneys, nephritis. See Medicine and Surgery.

Human calculi are commonly formed of different strata or incrustations; sometimes smooth and heavy like mineral stones; but often rough, spongy, light, and full of inequalities or protuberances; chemically analyzed, or distilled in an open fire, they yield nearly the same principles as urine itself; or at least an empyreumatic volatile urinous matter, together with a great deal of air. They never have, nor can have, naturally, any foreign matter for a basis: but they may by accident; an instance of which is related by Dr. Percival. A bougie had unfortunately slipped into the bladder, and upon it a stone of considerable size was formed in less than a year. This stone had to much the appearance of chalk, that the doctor was induced to try whether it could be converted into quicklime. His experiment succeeded, both with that and some other calculi; from which he conjectures, that hard waters which contain calcareous earth may contribute towards the formation of these calculi.