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ELEMENTS OF MATERIA MEDICA.
advantage over them in being less irritant, and thereby is not so apt tooccasion disorder of the digestive organs. It may be employed to neu-tralize acids introduced into the stomach from without, (as in cases ofpoisoning by the mineral acids) or to prevent the excessive formation of,or to neutralize when formed, acid in the animal economy. Thus it isadministered to relieve heartburn arising from, or connected with, thesecretion of an abnormal quantity of acid by the stomach : its efficacy isbest seen in persons of a gouty or rheumatic diathesis, in which theurine contains excess of uric acid. It often relieves the headache towhich such individuals are not unfrequently subject. It is most effica-cious in diminishing the quantity of uric acid in the urine, in calculouscomplaints, and according to Mr. Brande {Phil. Trans. 1813, p. 213) it issometimes effectual where the alkalies have failed. It will be found ofgreat value in those urinary affections in which alkaline remedies areindicated, but in which potash and soda have created dyspepticsymptoms.
As a laxative , magnesia is much employed in the treatment of the dis-eases of children. It is tasteless, mild in its operation, and antacid,—qualities which render it most valuable as an infant’s purgative. Inde-pendently of these, llufeland ascribes to it a specific property of dimi-nishing gastro-intestinal irritation by a directly sedative influence. Inflatulency it is combined with some carminative water (dill or anise); indiarrhoea, with rhubarb. It is employed as a purgative by adidts indyspeptic cases—in affections of the rectum, as piles and stricture—andin diarrhoea. It is associated with the carminative waters—with someneutral salts, as sulphate of magnesia, to increase its cathartic operation—or in diarrhoea, with rhubarb.
Administration. —As a purgative, the dose, for adults, is from ascruple to a drachm ; for infants, from two to ten grains. As an anta-cid, the dose is from ten to thirty grains twice a day. It may be conve-niently given in milk. It is sometimes administered in combination withlemon juice : the citrate of magnesia thus formed acts as a pleasantand mild aperient.
Magne'sice Subcar'bonas. — Subcar'bonate of Magne'sia.
History. —Subcarbonate of magnesia, also called magnesia alba andcarbonate of magnesia, was exposed for sale at Rome at the commence-ment of the 18th century, by Count di Palma, in consequence of which itwas termed Comitissce Palma; pulvis. In 1707, Y T alentini informed thepublic how it might be prepared.
Natural History. —Neutral carbonate of magnesia is found native invarious parts of Europe, Asia , and America. It constitutes a range oflow hills in Hindostan, from whence it has sometimes been imported inconsiderable quantities into this country, but has been found, as 1 aminformed, unsaleable here. The samples offered for sale about twoyears since consisted of reniform, opaque, dull masses, adherent to thetongue, having a conchoidal fracture, and considerable hardness. Inter-nally, they were whitish; externally, greyish or yellowish white. Thesame substance was brought over about a year ago in the calcined state,and was nearly white. It was called calcined Indian magnesia. Car-bonate of magnesia is found in some mineral waters.