This section is from the book "Materia Medica: Pharmacology: Therapeutics Prescription Writing For Students and Practitioners", by Walter A. Bastedo. Also available from Amazon: Materia Medica: Pharmacology: Therapeutics: Prescription Writing for Students and Practitioners.
The vehicle is the diluent or solvent. It is generally employed in sufficient quantity to make the dose a readily measurable amount. A vehicle maybe - (a) non-medicinal, as plain water, or a flavored liquid, or a mucilaginous liquid to hold heavy powders in suspension; or (b) it may have medicinal value. It is to be remembered that a prescription is often rendered more palatable and no less efficient through the medium of a pleasant tasting vehicle or an added flavor. The simple vehicles in common use are: water, the flavored waters (anise, cinnamon, peppermint, wintergreen, etc.), alcohol, sherry wine, aromatic elixir, elixir adjuvans (incompatible with acids), and the flavored syrups (citric acid, almond, ginger, wild cherry, orange-peel, orange-flowers, raspberry, rose, tolu, and the compound syrup of sarsaparilla which contains sarsaparilla, licorice, senna, sassafras, anise, and wintergreen).
Small amounts of special flavoring substances, with or without medicinal properties, are frequently added to prescriptions, especially where the vehicle is plain water or alcohol. Such are: (a) Sweetening agents, as sugar, glycerin, and the various syrups. In diabetes, saccharin, which dissolves in alkaline media, may be employed.
(b) Aromatics - the waters and spirits (bitter almond, anise, compound spirit of orange, cinnamon, lavender, peppermint, spearmint, and wintergreen), the elixirs, the fluidextract of licorice (incompatible with acids), the aromatic fluidextract (made of cardamom, ginger, cinnamon, and nutmeg), the tinctures of cardamom, cinnamon, ginger, lemon-peel, bitter orange, sweet orange, tolu, vanilla, the compound tincture of cardamom (made of cardamom, cinnamon, and caraway), and the compound tincture of lavender (made of lavender, rosemary, cloves, cinnamon, and nutmeg). Many of the flavored syrups combine sweetening and aromatic properties.
Bitter or unpleasant tastes in liquids may be overcome or partly so by these flavoring substances or by flavored vehicles. Bitterness may be especially overcome by the syrup of yerba santa. (See Part II.) Bitter or disagreeable solids are sometimes made up into flavored liquid mixtures.
Colors are sometimes added to watery-looking liquids for their psychic effect. The preparation seems more like "real medicine," and if it is a powerful remedy, is less likely to be mistaken for something harmless. Colored aromatic tinctures, like the compound tincture of lavender, may be employed, or tincture of persio, or carmine (in aqueous liquid).
(For definitions of the classes of liquids employed, see Part I.)