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.
This consists of the tops of Rosmarinus officinalis, an evergreen shrub, inhabiting the shores of the Mediterranean, and cultivated in the gardens of Europe and this country. As found in our shops, it consists chiefly of the leaves.
Sensible Properties. The leaves are distinguished by their linear shape, their length of an inch and more, their breadth about one-sixth of an inch, the faded greenness of their upper and the whiteness of their under surface, and by a singular folding backward of both edges, which causes the colour of their under surface to be Concealed on each side by a green border, leaving only a slender Streak of whiteness in the middle. They have a balsamic odour, and a bitterish and camphorous, taste, and yield these properties to water and alcohol, but much more freely to the latter.
Rosemary owes its virtues to a volatile oil, which is obtained by distillation with water. It is lighter than water, colourless, of an odour similar to that of the plant, but less agreeable, and a hot somewhat aromatic taste.
Rosemary, though in some degree aromatic, is more characterized by its stimulant and rubefacient properties. It agrees, however, with the aromatics, in being proportionably more stimulating locally, than upon the system at large. Some have believed it to possess eminenagogue properties; but when it has appeared to promote the menstrual discharge, it has probably been simply as a general stimulant. In this country it is seldom used internally, except as an ingredient in some officinal preparation, as the compound spirit of lavender. The Volatile Oil (Oleum Rosmarini, U. S., Br.) is recognized in both the U. S. and Br. Pharmacopoeias, though the leaves, from which it is procured, are rejected by the latter. It may be given as a carminative, or gastric stimulant, in the dose of from three to six drops. The Spirit (Spiritus Rosmarini, Br.) is made by dissolving the oil in alcohol, and is used almost exclusively either as a perfume, an ingredient in rubefacient liniments, or as one of the constituents of the compound spirit of lavender.