The salts of lead only are used in medicine, the official salts being as follows:

Plumbi Acetas - Plumbi Acetatis - Lead Acetate (U. S. P.) (Sugar of Lead). - Origin. - Metallic lead is dissolved in the presence of air, in acetic acid, or lead oxide is dissolved by the aid of a gentle heat in acetic acid and water, the solution being filtered, evaporated, and crystallized.

Description and Properties. - Colorless, shining, transparent, monoclinic prisms or plates, or heavy, white, crystalline masses, or granular crystals, having a faintly acetous odor and a sweetish, astringent, and afterward metallic taste. On exposure to the air, efflorescent and absorbing carbon dioxide. Soluble in 2 parts of water and in 30 parts of alcohol, in 0.5 part of boiling water, and in I part of boiling alcohol. Lead acetate should be kept in well-stoppered bottles.

Dose. - 1/2-5 grains (0.03-0.3 Gm.) [1 grain (0.065 Gm.), U. S. P.].

Liquor Plumbi Subacetatis - Liquoris Plumbi Subacetatis - Solution of Lead Subacetate (Goulard's Extract). - Used externally and locally. (The solution contains not less than 25 per cent. of lead subacetate.)

Liquor Plumbi Subacetatis Dilutus - Liquoris Plumbi Subacetatis Diluti - Diluted Solution of Lead Subacetate (Lead Water). - Used externally and locally. (It contains 1 per cent. of lead subacetate.)

Ceratum Plumbi Subacetatis - Cerati Plumbi Subacetatis - Cerate of Lead Subacetate (Goulard's Cerate). - Used externally and locally. (Goulard's extract, 20; camphor, 2; wool-fat, 20; paraffin, 20; white petrolatum, 38.)

Plumbi Iodidum - Plumbi Iodidi - Lead Iodide (U. S. P.). - Origin. - Obtained by mixing a solution of lead nitrate and potassium iodide, and drying the precipitate.

Description and Properties. - A heavy, bright-yellow powder without odor or taste. Permanent in the air. Soluble in about 1300 parts of water and in about 200 parts of boiling water, separating from the latter solution in brilliant golden-yellow spangles or crystalline laminae. Very slightly soluble in alcohol, but soluble, without color, in solutions of the fixed alkalies, in concentrated solutions of the acetates, of the alkalies, potassium iodide, and sodium hyposulphite, and in a hot solution of ammonium chloride. Lead iodide should be kept in well-stoppered bottles.

Dose. - 1/5 grain (0.013 Gm.).

Plumbi Nitras - Plumbi Nitratis - Lead Nitrate (U. S. P.). - Origin. - Prepared by dissolving lead in diluted nitric acid.

Description and Properties. - Colorless, transparent, octahedral crystals, or white, nearly opaque crystals, without odor and having a sweetish, astringent, and afterward metallic taste. Permanent in the air. Soluble in 1.85 parts of water; almost insoluble in alcohol. Used externally and locally.

Plumbi Oxidum - Plumbi Oxidi - Lead Oxide (U. S. P.) (Litharge). - Origin. - Obtained by roasting lead in air.

Description and Properties. - A heavy, yellowish or reddish-yellow powder or minute scales, without odor or taste. On exposure to air it slowly absorbs moisture and carbon dioxide. Almost insoluble in water and insoluble in alcohol. Soluble in acetic or diluted nitric acid and in warm solutions of the fixed alkalies. Lead oxide should be kept in well-closed vessels. Used externally and locally.

Emplastrum Plumbi - Emplastra Plumbi - Lead Plaster (Diachylon Plaster). - Used externally and locally.

(Lead oxide or lead plaster is contained in emplastrum ammoniaci cum hydrargyro and emplastra ferri, hydrargyri, opii, resinae, and saponis.)

Unguentum Diachylon - Unguenti Diachylon - Diachylon Ointment. -(Lead plaster, 50; olive oil, 49; oil of lavender flowers, 1.) Used externally and locally.

Physiological Action. - Lead per se is practically inert; some of its salts, however, particularly the acetate, possess valuable therapeutic properties.

Externally and Locally. - Applied to the unbroken skin, solutions of lead salts have little, if any, effect, yet they act readily upon denuded surfaces, blanching the tissue of the parts by contraction of the small blood-vessels. They coagulate the albumin of the protoplasm of the neighboring superficial cells, and the coagulum being insoluble in an excess of the lead salt thus forms a protective coating for the healthier structure beneath.

These salts have likewise a sedative action because of the decreased local circulation. The nitrate alone is irritating because of the nitric acid ion.

Internally. - Digestive System. - Lead acts immediately in the mouth, causing a sweet, styptic taste and coagulating the mucus. It contracts the cells and vessels of the entire alimentary canal, inducing dryness by diminished secretion. Consequent to the disturbed physiological functions of the digestive tract, the peristaltic movements diminish, and constipation necessarily ensues.

In small amounts lead salts have practically no action on the various cerebral or medullary functions. In chronic poisoning these are markedly affected.

Absorption and Elimination. - The preparations of lead are converted in the stomach into albuminates; and thence taken up by the blood, very little absorption taking place in the intestine, where the lead is converted into an insoluble sulphide. It is absorbed by the abraded skin, and enters directly into combination with the albumin of the tissues. A portion of the lead albuminate is eliminated by the liver with the bile into the intestine, where, being converted into a sulphide, it is excreted in that form with the feces. The skin, kidneys, and mammary glands assist in its elimination.

Excretion is very slow, the liver and kidneys retaining lead for a long time.

Uterus. - Under the influence of lead, abortion is liable to occur or the child be still-born.

Untoward Action. - Undesirable results have followed the administration of medicinal doses of lead acetate, evidently arising from insufficient elimination. Baker observed loss of appetite, gas-tralgia, constipation, and paralysis of three weeks' duration. This last symptom occurred in the hand of a man who had taken 1 grain (0.06 Gm.) of lead acetate twice daily for four days to relieve hematuria. In another case attacks of colic, lasting several months, followed the exhibition of 4 grains (0.25 Gm.) of the same salt for three days. Tanquere des Planches suggests caution in too free an administration of lead preparations, as being prone to occasion disagreeable symptoms. Hair dyes should be remembered in this connection.