=Lead.=—The preparations of lead are used internally and externally as sedatives and astringents. _Lead Acetate_ (Plumbi Acetas) is employed internally in diarrhea. The _dose_ is from 1 to 3 grains (0.06-0.2 gm.), in pill form. The _Solution_ of _Lead Subacetate_ (Liquor Plumbi Subacetatis) is employed externally. Diluted with from 5 to 6 parts of water it is used as a sedative application in ivy-poisoning and erysipelas. The _Dilute Solution_ of _Lead Subacetate_ (Liquor Plumbi Subacetatis Dilutus) is known as _lead-water_, and is chiefly employed in making the sedative preparation known as lead-water and laudanum. As usually dispensed it contains 1 dram (4 c.c.) of laudanum and 4 drams (15 c.c.) of lead-water to 2 ounces (60 c.c.) of water. _Acute lead-poisoning_ is characterized by a burning pain in the abdomen, a metallic taste in the mouth, vomiting, purging, coma, and collapse. _Chronic lead-poisoning_ is characterized by anemia, intestinal colic, constipation, a blue line on the gums (deposit of lead sulphide), and paralysis of the forearms (wrist-drop). =Magnesium Sulphate (Epsom Salt).=—This salt is an excellent hydragogue cathartic, producing in the course of a few hours copious watery stools. It is also employed as an antidote in acute lead-poisoning and carbolic-acid poisoning. To secure the most prompt and powerful cathartic effect the drug is best given before breakfast, in a single dose, and with but a small quantity of water. _Dose_, from 1 to 8 drams (4-31 gm.). =Magnesium Oxid (Magnesia).=—This is a white, tasteless, and insoluble powder. It is a cathartic, but much milder in action than Epsom salt. _Dose_, from 10 to 60 grains (0.6-4 gm.). =Magnesium Citrate.=—An effervescing solution of this drug is much used as an agreeable laxative. The _dose_ is from 6 to 12 ounces (180-360 c.c.). =Mercury.=—The most important preparations of this metal are calomel, blue mass, corrosive sublimate, oxid of mercury, iodid of mercury, nitrate of mercury, and ointment of mercury. _Calomel_ (Hydrargyri Chloridi Mite).—This preparation is employed internally as a cathartic and gastric sedative, and externally as a stimulating and antiseptic dusting-powder. As a cathartic its best effect is secured by giving it in _doses_ of from ⅒ to ⅙ grain (0.006-0.01 gm.) every half-hour or hour, until a grain has been taken. In this way the whole amount ingested is absorbed. When large doses are employed much of the drug escapes absorption.