This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Nasturtium Aquaticum Pharm. Lond. & Edinb. Nafturtium aquaticum fupinum C. B. Sifymbrium aquaticum Tourn. Creffio qui-bufdam. Sifymbrium Nafturtium aquaticum Linn. Water cresses: a juicy plant, with brownish, oblong, obtuse leaves, set nearly in pairs, without pedicles, on a middle rib, which is terminated by an odd one larger and longer-pointed than the reft: the stalks are hollow, pretty thick, channelled, and crooked: on the tops grow, tufts of small tetrapetalous white flowers, followed by oblong pods, which bursting throw out a number of roundish seeds. It grows in rivulets and the clearer standing waters, and flowers in June: the leaves remain green all the winter, but are in greatest perfection in the spring.
The leaves of the water creffes have a moderately pungent taste; and, when rubbed betwixt the fingers, emit a quick penetrating smell, like that of mustard seed, but much weaker. Their pungent matter is taken up both by watery and spirituous menstrua, and accompanies the aqueous juice which issues copiously upon expression: it is very volatile, so as to arise, in great part, in distillation with rectified spirit as well as with water, and almost totally to exhale in drying the leaves, or in-fpiffating by the gentlest heat, to the consistence of an extract, either the expressed juice, or the watery, or spirituous tinctures: both the in-fpiffated juice and the watery extract discover to the taste a saline impregnation, and in keeping throw up crystalline efflorescences to the surface. On distilling with water considerable quantities of the herb, a small proportion of a subtile, volatile, very pungent essential oil is obtained.
This herb is one of the milder acrid, aperient, antiscorbutics; of the same general virtues with the cochlearia, but considerably less pungent, and in great measure free from the peculiar flavour which accompanies that plant. Hoffman has a great opinion of it, and recommends it as of Angular efficacy for strengthening the viscera, opening obstructions of the glands, promoting the fluid secretions, and purifying the blood and humours: for these purposes the herb may be used as a dietetic article, or the expressed juice taken in doses of from one to four ounces twice or thrice a day.