=Atropin.=—See _Belladonna_. =Belladonna.=—This drug owes its activity to the alkaloid _atropin_. It is employed internally to stimulate the respiration; to stimulate the circulation; to allay local spasm, as in asthma and whooping-cough; to check excessive secretion, as in the night-sweats of phthisis; and to stimulate peristalsis in atonic constipation. Locally, it is employed in the form of solutions of atropin to dilate the pupil of the eye, and in the form of a liniment or plaster of belladonna as a sedative application in various inflammatory conditions. Toxic doses of belladonna cause dilatation of the pupils, dryness of the throat, quickening of the pulse and respiration, delirium, and a diffuse red rash resembling that of scarlatina. The _dose_ of _atropin_ is from ¹/₁₅₀ to ¹/₅₀ grain (0.00043-0.0013 gm.); of the _Tincture of Belladonna_ (Tinctura Belladonnæ), 5 to 20 minims (0.3-1.2 c.c.); of the _Extract of Belladonna_ (Extractum Belladonnæ), ⅛ to ¼ grain (0.008-0.016 gm.). =Bismuth.=—The insoluble preparations of the metal—_subnitrate_, _subcarbonate_, and _subgallate_—are used internally as mild antiseptics, sedatives, astringents, and antacids in various inflammatory diseases of the stomach and bowel. They are scarcely poisonous when taken internally in any amount. The usual _dose_ of any one of the preparations named is from 5 to 30 grains (0.3-2 gm.) in dry powder or stirred in milk or water. =Bromids.=—The salts of bromin in common use are the bromids of potassium, sodium, ammonium, and strontium. The action of these is very similar. They are especially useful as depressants to the central nervous system. They are employed to produce sleep, to check convulsions, and to relieve headache and neuralgic pain. Large doses depress the heart and respiration. The continued use of the bromids causes a condition known as _bromism_. This is characterized by fetor of the breath, a rash on the skin, languor, and somnolence. The _dose_ of the _bromin salts_ is from 10 to 60 grains (0.6-4 gm.). =Caffein.=—This is an alkaloid obtained from coffee. It is a heart stimulant, respiratory stimulant, brain stimulant, and kidney stimulant (diuretic). The _dose_ is from 1 to 5 grains (0.06-0.3 gm.). =Calomel.=—See _Mercury_.