Agents Acting on the Circulation.

Cardiac Stimulants,—are such agents as rapidly increase the force and frequency of the pulse, in depressed conditions of the cardiac apparatus. The most rapid, energetic and available agents of this class are Ether, Alcohol, Heat and Ammonia, the last-named also stimulating the vaso-motor centre. The list also includes—Sparteine, Atropine, Cocaine, Morphine (in small doses), Camphor, Chloroform, Turpentine, the Aromatic Oils, Counter-irritation, the continuous Galvanic Current, Nitro-glycerin, etc.

Cardiac Tonics,—in moderate doses stimulate the cardiac muscle, slowing and lengthening its contractions ;—but in large doses they produce irregular action of the heart, and some of them may cause sudden death by syncope if pushed to any great extent. The typical agent of this class is Digitalis, which also contracts the arterioles and greatly increases the blood. Others, less powerful and correspondingly safer, are — Convallaria, Strophanthus, Squill, Cimicifuga and Erythrophloeum. The list also includes Caffeine, Strychnine, Helleboreïn and Adonidin (from Adonis vernalis).

Cardiac Sedatives,—lessen the force and frequency of the heart's action. They are used to control palpitation and overaction of that organ, also to slow the pulse in febrile conditions in sthenic subjects, especially when local inflammation is the exciting cause thereof. Most of them are direct cardiac depressing both the heart-muscle and the motor ganglia. The list includes Aconite and Veratrum Viride, also Muscarine, Pilocarpine, Saponin, Hydrocyanic Acid, Antimony, Potassium salts and Digitalis,—the last-named acting as a sedative by stimulation of the vagus centre and the cardiac muscle, slowing the rate and giving regular rhythm to the action of the heart.

Vascular Stimulants,—dilate the peripheral vessels, and increase the peripheral circulation thus equalizing blood-pressure and preventing internal congestions, The most useful are Alcohol and Ether, as they stimulate the action of the heart simultaneously with the vascular relaxation. The other chief members of the group are—Nitrites, Nitro-glycerin, Nitrous Ether, Liquor Ammonii Acetatis, Opium with Ipecac, (as in Dover's powder), and Heat, applied locally by poultices, etc.

Vascular Tonics and Sedatives,—are a group of agents which increase the contractile power of the arterioles, thereby lessening the capillary circulation, and raising the blood-pressure. They do this by a stimulating action upon either the vaso-motor centre or its mechanism in the walls of the vessels. Their most important uses are the checking of hemorrhages, and the cutting short of local inflammations. This group is well represented by Ergot and Digitalis, and besides these it includes—Squill, Opium in small closes, Strychnine, Salts of Iron, Lead and Silver, Hamamelis, and Cold, applied locally, as by the Ether spray, or by evaporating lotions containing Alcohol, Vinegar, Ammonium Chloride, etc.

A Compend of Materia Medica, Therapeutics, and Prescription Writing, 1902, by Sam'l O. L. Potter, M.D., M.R.C.P.L.