Calomel. Hydrargyri Sub-chloridum. Sub-chloride of Mercury. Hg2Cl. Hydrargyri Chloridum. Chloride of Mercury (Pharm. Lond.). Called also the Protochloride,' the Muriate and the Mild Muriate of Mercury. Comp. Mercury 84.92, Chlorine 15.08, in 100 parts; or 2 Eq. Mercury (2 x 100) = 200 + 1 Chlorine = 35.5 = 235.5, Eq. Wt.

Med. Prop. and Action. Alterative, in doses of gr. 1/2 - j., either alone, or as it occurs in Hummer's Pill. Purgative, gr. ij. - vj. in combination with Jalap,

* Med. Times, vol. xviii. p. 304.

Diseases of the Skin, pp. 266, 295.

Scammony, and other purgatives. When it is wished to bring the system under the specific influence of Mercury, the dose is gr. j. - gr. ij. or more, frequently repeated, with a small portion of Opium to prevent its passing off by the bowels. It is said to have a sedative action in doses of gr. xx. - gr. lx. It is best given in the form of pill, with some inert confection. Externally it is applied in the form of ointment, or as a lotion, with Liq. Cakis (rulgo black wash), or in the form of powder. Calomel is the best salt of Mercury for rapidly and certainly brining the system under the influence of the metal, and is consequently preferable in all acute inflammations. Its modus operandi is imperfectly understood; a small dose evidently increases the activity of the liver and biliary organs, as is shown by the character of the stools which are produced by it: in doses of gr. xx. in acute dysentery, its sedative action is often very evident, and the benefit which avisos from it in Croup, and other affections of the throat; has led to the belief that it acts specifically upon the lining membrane of the tracbca and larynx; no less certain and evident is its action on the salivary glands. of all medicines in the Materia Medica, none is of more genoal utility and efficacy, when used with judgment, than Calomel. In some idiosyncrasies it produces most serious effects.

Offic Prep. 1. Pilula Calomelanos Composita. Plummer's Pill (See art. Calomelanos Pil. Comp.)

2. Unguentum Calomelanos (Calomel Grs

lxxx.; Prepared Lard oz. j.).

Dose of Calomel: as a purgative, gr. ij. - gr. x.; to produce mercurial specific effects, gr. j. - ij., or more, frequently repealed.

Incompatible*. Alkalies, and their Carbonates; Acids; Lime Water; Salts of Iron, Lead, and Copper; the Chlorides and Hydrosulphurets.

1376. Therapeutic Uses

In Acute Sthenic Inflammation, particularly in that of Serous Membranes, the experience of the highest authorities, for the last seventy years, has proved Calomel to be a remedy of the highest value. It is commonly said that it exerts a twofold action: one, antiphlogistic, constraining the morbid action of the blood-vessels, particularly the capillaries; the other, reparatory, that is, aiding the reparation of parts by removing the substances foreign to them. * Mr. Hemy Smith has suggested that its action is confined to the blood, in which it effects such an alteration as to incapacitate it from effusing lymph, thus virtually putting an end to inflammatory action. He adduces many ingenious arguments to prove the correctness of his theory; and it certainly bears the appearance of truth. In many cases local or general blood-letting should precede the administration of Calomel in acute inflammation. When, however, this rule has not been observed, and the disease has been allowed to progress for some period unchecked, Calomel, either alone or combined with Opium, frequently gives the patient the best chance of recovery. The combination of Calomel and Opium, in the treatment of acute inflammation, was first proposed, in 1783, by Dr. Hamilton, of Lynn Regis, who employed it successfully in Hepatitis and in other inflammatory affections. The late Dr. Armstrong emphatically said of this treatment, that " it deserves to be written in letters of gold, on account of its great practical

* See Latham on Diseases of the Heart. Med. Times, vol. xvi p. 132.

Duncan's Med. Commentaries, vol. ix. 1783.

utility." The Opium relieves the pain and irritation, and calms the nervous system; at the same time that the Calomel controls the action of the capillaries, impoverishes the quality of the blood, and arrests the effusion of lymph. Some writers have erroneously attributed the value of this combination to the Opium alone, but Mr. H. Smith,* with much justice, observes, "It would be folly to give the Opium without the Mercury, but it would be a cruelty to give the Mercury without the Opium." Indeed, it appears that in combination they possess an antiphlogistic power, which either of them, employed singly, is not capable of producing. We cannot be sure, observes Dr. Watson, that Mercury exercises its full influence on the system, unless we produce a degree of soreness of the gums; and the earlier this can be induced the better. Some practitioners believe that a combination of Calomel and Blue Pill acts sooner and answers better than a proportional dose of either given alone. The general formula employed is, Calomel gr. j. - iij., Opium gr. 1/2 to gr. j., repeated every six or four hours, according to the urgency of the disease. Antimony may be in some cases advantageously conjoined. (See Antim. Tart.) Saline medicines and an antiphlogistic diet should be enforced. When it is an object to obtain a speedy effect on the system, mercurial inunction should be employed together with its internal use.