The only preparation of bismuth used in medicine was for a long time the subnitrate; but the subcarbonate has been of late introduced as a substitute, and is now recognized in the U. S. Pharmacopoeia; and a preparation containing the citrate of the metal with ammonia has recently been introduced, with the advantage that it may be used in the liquid form; the others being insoluble. These three preparations will be treated of under the present heading.