white powder, insoluble in water, and free from grittiness, but possessing no superiority over prepared chalk.

CRETA PREPARATA (Prepared Chalk), is made from chalk or whiting, by levigation and elutriation. It occurs in little white conical loaves, which are tasteless, odourless, insoluble in water, but more soluble in carbonic acid water. It consists of one eq. of carbonic acid and one of lime (CaO,CO). Its effects are those of an absorbent, antacid, and desiccant astringent. It is used in dyspepsia and gout, attended with an excess of acid in the system; also in diarrhoea; and, as it forms soluble. salts of lime with the acids of the stomach, its employment has been suggested in rachitis. Dose, gr. x-xxx, in powder, or suspended in water with gum and sugar. Mistura Creta (Chalk Mixture), consists of prepared chalk (half a troyounce), rubbed up with gum arabic (120 grains), and water (4 fluidounces), and afterwards mixed with glycerin (half a fluidounce), and cinnamon water (4 fluidounces); dose, f3ss, repeated. Laudanum, and tincture of kino or of catechu, and aromatics, are often added to this mixture, in the treatment of diarrhoea. Troches of chalk are made by mixing 4 troyounces of prepared chalk, a troyounce of gum arabic, 60 grains of nutmeg, and 6 troyounces of sugar, and forming with water a mass, to be divided into 480 troches, each containing 4 grains of prepared chalk.

TESTA PRÆPARATA (Prepared Oyster-shell), differs from prepared chalk, in containing animal matter united with the carbonate of calcium, and is thought to be more acceptable to a delicate stomach. Dose, gr. x-xxx.

CLASS IV.-TOPICAL MEDICINES.

ORDER I.-IRRITANTS.

Irritants are medicines which are employed to produce irritation or inflammation of the parts to which they are applied. They may be subdivided into RUBEFACIENTS, EPISPASTICS, SUPPURANTS, and ESCHAROTICS. Rubefacients are used merely

to produce redness of the skin. Epispastics, or vesicants, cause the exhalation of a serous fluid under the cuticle. Suppurants produce a crop of pustules. Escharotics have a chemical action on the tissues with which they are placed in contact, and decompose or destroy them.

RUBEFACIENTS.

Rubefacients are employed to remove congestion and inflammation, to rouse the capillary system in cases of local torpor, to relieve pain and spasm, and as stimulants to the general system, in coma, syncope, asphyxia, &c. They are adapted to cases in which a sudden and powerful, but transient action is called for; but they may also be employed where a slight and long-continued action is desired. In removing congestion and inflammation, rubefacients act by revulsion. They are chiefly useful in the forming stages or in light grades of inflammation. They are very serviceable local anodynes, when applied to painful parts-acting by a substitutive influence. As general stimulants, their efficacy in rousing the system depends partly on their action on the capillary circulation, and partly on the pain which they produce. They are most valuable in the coma or asphyxia resulting from poisons, drowning, &c., and are inferior to blisters in the cerebral oppression, which occurs in fevers, inflammations of the brain, &c.

Rubefacients are usually applied till pain and redness supervene. If kept too long on the skin, many of them will produce vesication and even gangrene; and, in cases of coma, particular caution is required, as the patient may not feel them till dangerous inflammation has occurred.

SINAPIS-MUSTAR D.

MUSTARD-SEEDS are obtained from two varieties of Sinapis, -S. nigra, or Black Mustard, and S. alba, or White Mustard (Nat. Ord. Brassicaceae), small annual European plants, cultivated in our gardens. S. nigra has become naturalized in

white powder, insoluble in water, and free from grittiness, l possessing no superiority over prepared chalk.

Its

CRETA PREPARATA (Prepared Chalk), is made from c or whiting, by levigation and elutriation. It occurs in white conical loaves, which are tasteless, odourless, insolu water, but more soluble in carbonic acid water. It cons one eq. of carbonic acid and one of lime (CaO,CO2). are those of an absorbent, antacid, and desiccant ast It is used in dyspepsia and gout, attended with an acid in the system; also in diarrhoea; and, as it form salts of lime with the acids of the stomach, its employ been suggested in rachitis. Dose, gr. x-xxx, in 1 suspended in water with gum and sugar. Mist (Chalk Mixture), consists of prepared chalk (half a rubbed up with gum arabic (120 grains), and wa ounces), and afterwards mixed with glycerin (half: and cinnamon water (4 fluidounces); dose, f Laudanum, and tincture of kino or of catechu, a are often added to this mixture, in the treatment Troches of chalk are made by mixing 4 troy pared chalk, a troyounce of gum arabic, 60 gr: and 6 troyounces of sugar, and forming with w be divided into 480 troches, each containing pared chalk.

TESTA PRÆPARATA (Prepared Oyster-shell). pared chalk, in containing animal matter un bonate of calcium, and is thought to be mo delicate stomach. Dose, gr. x-xxx.

tinued, it will develop vesication, ulceration, and even sphacelus. Mustard-seeds, swallowed whole, have been used as a laxative in dyspepsia, in the dose of a tablespoonful once or twice a day, mixed with molasses; the white seeds are preferred. When mustard is employed internally, however, it is chiefly as an emetic, in cases of torpor of the stomach, particularly after narcotic poisoning; and, by its stimulant action, mustard often. rouses the gastric susceptibility when other emetics fail. Dose, as an emetic, from a large teaspoonful to a tablespoonful of the bruised seeds or powder. Its use in smaller quantity, as a condiment and stimulant of the digestive organs, is well known. In the form of whey (half a troy ounce boiled in milk Oj), it is given as a diuretic in dropsy. The most general use of mustard is, however, as a cutaneous stimulant, in the form of cataplasm (termed a sinapism). This is made by mixing flour of mustard with a sufficient quantity of tepid water to give it proper consistence; and it may be diluted with wheat or rye flour, if a weaker effect is desired. Sinapisms are used, when a speedy and powerful rubefacient effect is required: they should be kept on till pain and redness are produced, usually from a quarter of an hour to an hour, and, in cases of insensibility, their effects should be carefully watched. They are applied spread on linen, and covered with gauze, to prevent adhesion to the skin.

For ready use, there is now kept in the shops Charta Sinapis (Mustard paper), which is prepared by mixing 90 grains of black mustard (in powder), with enough solution of gutta-percha to give it a semi-liquid consistence, and then applying the mixture by a brush to a piece of stiff paper, 4 inches square; before being applied to the skin, it should be dipped for about 15 seconds in warm water.

CAPSICUM.

Capsicum has been previously noticed as an aromatic stimulant (p. 177). It is a powerful rubefacient, useful in rheuma tism, low fevers, &c., and is applied in the form of cataplasm, or the tincture or oleoresin may be used.

OLEUM TEREBINTHINE-OIL OF TURPENTINE.

The oil of turpentine (see p. 271), is a speedy and efficacious rubefacient, and sometimes produces a vesicular eruption. It is employed in low forms of disease, attended with coldness of the surface; as a counter-irritant in inflammation; and as a stimulating liniment in rheumatic and paralytic cases. It is often diluted with olive oil.

LINIMENTUM

AMMONIE-LINIMENT OF AMMONIA.

This preparation, called also volatile liniment, consists of one fluidounce of water of ammonia (see p. 174), and two troyounces of olive oil. It is an excellent application, as a counter-irritant, in affections of the throat and chest, &c.

PIX BURGUNDICA-BURGUNDY PITCH.

This is the prepared RESINOUS EXUDATION from Abies excelsa or Norway Spruce (Nat. Ord. Pinaceae), a lofty evergreen tree of Europe and Northern Asia. Abies picea, or the European Silver Fir, is said to be also a source of the drug. It is obtained by stripping off the bark, and detaching the flakes of resinous matter which form upon the surface of the wound; they are afterwards melted in boiling water and strained. Burgundy pitch is principally collected in Germany and France, and derives its name from Burgundy, in the latter kingdom. After it is imported into the United States, it is generally re-melted and strained, to free it from impurities; and, as found in the shops, it is a hard, brittle, opaque substance, of a yellowish or brownish-yellow colour, and a weak terebinthinate taste and smell; when applied to the body, it softens and becomes adhesive. It contains two resins, and a much smaller proportion of volatile oil than turpentine.

A spurious Burgundy pitch is made by melting together