This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Carduus Benedictus Pharm. Lond. & Edinb. Cnicus silvestris birsutior five carduus benedict us C. B. Centaurea benedicta Linn. Holy thistle: a plant with rough, narrow, jagged leaves, terminating in soft prickles; and large, hairy, branched stalks, leaning to the ground; on the tops of which grow large, scaly, prickly heads, including a number of yellow flofculi, which are followed by oblong striated seeds inclosed in down. It is a native of Spain and some of the islands of the Archipelago, and sown annually with us in gardens.
The leaves of carduus have a penetrating bitter taste, not very strong, or very durable in the mouth; accompanied in their recent state, with somewhat of an ungrateful flavour, which they soon lose in keeping. The herb, when thoroughly dried, should be hung up loosely in an airy place; being very subject, if pressed close, to rot or grow mouldy.
Cold water, poured on the dry leaves, extracts, in an hour or two, a light grateful bitter-ness: by standing long upon the plant, the liquor becomes disagreeable: a strong decoction is very nauseous and offensive to the stomach. A cold infusion and a decoction being separately infpiffated, the same differences were observed between the extracts, as between the liquors in their dilute state; the extract obtained from the infusion being a sufficiently agreeable bitter, and that from the decoction disgustful; a proof, that the differences of the liquors do not de-depend, as might be supposed, on their degree of saturation, but on their being impregnated with matters of a different kind.
Rectified spirit also extracts, in a short time, the lighter bitter part of the carduus, but does not take up the nauseous near so easily as water: a spirituous tincture prepared by warm digestion for several hours, and the extract obtained by infpiffating it, were more strongly but not unpleasantly bitter. The colour of the watery tinctures is a yellowish or greenish, inclining more or less to brown, according as they are more or less saturated; that of the spirituous, a deep green.
On keeping the soft watery extracts for some months, a considerable quantity of saline matter was found to have shot upon the surface, into small crystals, in shape approaching to those of nitre, in taste bitterish with an impres-sion of coolness.
The virtues of this plant seem to be little attended to in the present practice. The nause-ous decoction is sometimes used to excite vomiting, and a strong infusion to promote the operation of other emetics: but this elegant bitter, when extracted from the offensive parts of the herb, may be advantageously applied to other purposes. I have frequently observed excellent effects from a light infusion of carduus, in weakness of appetite and indigestion, where the stomach was injured by irregularities and oppressed by viscid phlegm: nor have I found any one medicine of the bitter kind to fit so easily on weak stomachs, or to heat so little. These infusions, taken freely, promote the natural secretions. Drank warm in bed, they commonly increase perspiration or excite sweat; and as they act with great mildness, not heating or irritating considerably, they have been used, in this intention, in acute as well as chronical diseases.
The seeds of carduus are likewise considerably bitter, and have sometimes been used as sudorifics or diaphoretics, in the form of emul-sion. Cartheufer observes, that they give the proper consistence of an emulsion to ten times their weight or more of water: and that they do not impart a perfect whiteness, but a greyish colour to the liquor.