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Materia Medica.

Part II.

black, an agreeable aromatic smell, and a very hot bitingtaste.

It is very often adulterated ; and sometimes what is sold forPeruvian balsam is a spurious mixture of resin and essentialoil, flavoured with benzoin. These frauds are not easily de-tected, and fortunately they are of little importance.

It is said to be obtained by boiling the cuttings of the twigsin water, and skimming off with a spoon the balsam, whichswims on the top.

By incision this tree yields a much more fragrant white orcolourless balsam, which, when inspissated by the heat of thesun, forms the red or dry balsam of Peru ; but it is very rare-h used in Britain, and almost never to be met with in ourshops.

Peruvian balsam consists of a volatile oil, resin, and benzoicacid ; it is, accordingly, entirely soluble in alcohol, and in es-sential oils. Water dissolves part of the benzoic acid, andfixed oil combines with the resin. It may be suspended in wa-ter by trituration with mucilage and yolk of egg.

Medical use __Balsam of Peru is a very warm aromatic me-dicine, considerably hotter and more acrid than copaiva. Itseffects are stimulating and tonic. Hence its use in some kindsof asthmas, gonorrhceas, dysenteries, suppressions of the ute-rine discharges, and other disorders proceeding from debility.It is also employed externally for cleansing and healing woundsand ulcers, and sometimes against palsies and rheumatic pains.

Mykrha, gummi-resina. Ed. Lond. Dub.Myrrh. The gum resin of a non-descript tree.

The tree which produces this gum-resin is not yet ascer-tained. Mr Bruce has given some reasons for supposing thatit is a mimosa; but we may observe, that all the mimosas, withwhich we are sufficiently acquainted, furnish a pure gum, andnot a gum-resin. The best myrrh is brought from Troglody-titia, a province of Abyssinia, on the borders of the Red Sea;but what we receive comes from the East Indies, and is pro-duced on the eastern coast of Arabia Felix.

The best myrrh is in the form of tears, of a yellow or red-dish yellow colour, becoming redder when breathed on ; light,brittle, of an unctuous feel, pellucid, shining; presenting whitesemicircular striae in their fracture; of a very bitter aromatictaste, and a strong, peculiar, not unpleasant odour. It is notgood if whitish, dark-coloured, black, resinous, ill smelled, ormixed with impurities, which is too commonly the case.