(From infundo, to pour in ). Infusion-. It signifies either the action of the fluid, or the medicine prepared by it.

By infusion in water, the gummy, the extractive, and the saline parts of vegetables, are separated: and by the intervention of the gum, the resin and oil are in part taken up by the same menstruum, so that in many instances the whole virtue of a plant is obtained. In general, water takes up more by infusion from dry herbs than from fresh ones, particularly the newly dried ones. From animal substances, water extracts the gelatinous and nutritious parts; and by this means glues, jellies, and broths, are prepared; and along with these it sometimes takes up principals of more activity. Water also generally suspends some portion of calcareous and aluminous earth; the quantity it dissolves of either is truly inconsiderable.

In making infusions, whether in cold or hot water, the ingredients are only steeped in it, without boiling. It is the same, whether proof spirit, rectified spirit, or any other menstruum, is employed, though these preparations have a different title. This form is preferred where the medicinal portion is soluble and easily separated; when it is volatile, and would fly off by boiling; or where it would be lost or destroyed by long maceration.

In nervous disorders, infusions are best made in a vinous, a spirituous, or an alkaline menstruum. Stomachic infusions should be moderately spirituous. Cathartic ones, whether saline or resinous, if for extemporaneous use, are best made with hot water.

Infusions should not, if possible, be so fully impregnated with the ingredients as to make the medicine unpalatable: though the infusions of many of the fetid plants must be necessarily unpleasing.

Many infusions are most agreeable when made with cold water, though probably weaker than when heat is employed. The cold infusion of camomile flowers and the carduus benedictus are pleasant, and will not excite vomiting.

Infusio. Sec Transfusio.