This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Gaultheria consists of the leaves of Gaultheria procum-bens, an indigenous, small, shrubby evergreen, inhabiting the woods or hill-sides, and dry sandy plains, from Canada to Georgia. It has a creeping, horizontal root, from which, at short intervals, erect stems arise, a few inches high, bearing the leaves near the summit, and a small spherical, scarlet, berry-like fruit. The plant is known by other names, as tea-berry, mountain-tea, winter-green, etc.
Sensible Properties. The leaves, which are the officinal part, are ovate or obovate, an inch or more in length, acute, revolute at the edges, with a few mucronate serratures, coriaceous, shining, of a bright-green colour on the upper surface, and paler beneath. These, as well as the whole plant, including the fruit, have a peculiar fragrant odour and aromatic taste, very similar to that of the Betula lenta or sweet-birch, and ascribable to a volatile oil, which is the same in both plants, and exists also in some others having similar sensible properties. Besides their aromatic properties, the leaves have a deeided astringency, and the fruit is sweet.
Active Principle. The volatile oil is obtained by distillation with water. It is the heaviest of all known volatile oils, having the specific gravity 1.173. When first procured, it is nearly colourless; but as found in the shops, is generally brownish-yellow or reddish. The odour is that of the plant, the taste sweetish, somewhat pungent, and very peculiar.
Gaultheria is a gently stimulant aromatic, and feeble astringent. For these properties, it has been used in some cases of chronic diarrhoea, and with supposed benefit. Like many other aromatics, it has been given as an emmenagogue; but has no other claim to this title than such as its gently stimulating property may give it. As a stomachic cordial and carminative, and for the relief of the flatulent colic of infants, it may be used like other aromatics, over which, however, it has no superiority. It has been sometimes used by people in the country, in the form of infusion, as a substitute for common tea. Its chief claim to notice, however, rests on its remarkable, and very peculiar flavour, which serves to characterize preparations, into the composition of which either the leaves or the volatile oil enter.
The Oil (Oleum Gaultheriae, U. S.) is more or less employed throughout the country, dissolved in alcohol in the form of an essence, for the same purposes as the oils of the mints. It may be prepared in the same way, and given in the same dose, as the essence of spearmint. In large quantities, the oil is capable of producing inflammation of the gastric mucous membrane. A case is on record in which half an ounce was swallowed, and occasioned the most alarming gastric symptoms, though the patient recovered. In the quantity of about a fluidounce. it is stated to have caused death in several instances, leaving strong marks of inflammation of the stomach. The oil is an ingredient of the Compound Syrup of Sarsaparilla of the U. S. Pharmacopoeia.