This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Tea: the leaf of a Chinese shrub, evonymo affinis arbor orientalis nucifera flore roseo Pluk. alm. Thea bohea &. viridis Linn. The leaves, carefully picked, are dried hastily on warm iron plates; whereby they are said to lose in great measure some noxious qualities which they have when fresh, and to preserve their admired flavour which by slow exsiccation would be soft. The several sorts of tea brought to us are supposed to be the leaves of the same plant, collected at different times, and cured in a somewhat different manner: Neumann suspects that the brown colour, and the flavour, of the bohea sorts, are introduced by art.
(a) Vide Memoires de l'acad. roy. des friends de Paris, pout Vann. 1700.
Both the green and bohea teas have an agreeable smell, and a lightly bitterish sub-astringent taste: with solution of chalybeate vitriol, they strike an inky blackness. They give out their smell and taste both to watery and to spirituous menstrua: to water, the green sorts communicate their own green tincture, and the bohea their brown: to rectified spirit they both impart a fine deep green. On gently drawing off the menstrua from the filtered tinctures, the water is found to elevate nearly all the peculiar flavour of the tea, while rectified spirit brings over little or nothing, leaving the smell as well as the taste concentrated in the extract: both extracts are very considerably astringent, and not a little ungrateful; the spirituous most so.
Infusions of tea, as dietetic articles, haves been extravagantly commended by some and condemned by others; and notwithstanding the frequency of their use, they real effects are scarcely as yet clear. They seem, when moderately used, to be for the most part innocent: in some cases, they seem to be salutary: in some, they are apparently prejudicial. They dilute thick juices and quench thirst more effectually, and pass off by the natural emunctories more freely, than mere watery fluids: they refrefh the spirits in heaviness and sleepiness, and seem to counteract the operation of inebriating liquors. From their manifest astringency, they have been sup-posed to Strengthen and brace up the solids, but this effect experience does not countenance: it is in disorders, and in constitutions, wherein corroborants are most serviceable, that the immoderate use of tea is peculiarly hurtful; in cold indolent habits, cachexies, chloroses, drop-sies, and debilities of the nervous system.
Thlaspi: a plant with oblong narrow undivided leaves joined immediately to the stalks, on the tops of which grow numerous tetrape-talous flowers, each of which is followed by a short flat feed-vessel divided transversely into two cells.
1. Thlaspi arvense siliquis latis C. B. 'Thlaspi arvense Linn. Treacle-mustard: with roundish-pointed jagged leaves, and broad capsules containing about four feeds in each cell. It is annual, and grows wild in corn-fields.
a. Thlaspi arvense, vaccarta incano folio majus C. B. Thlaspi campestre Linn. Mithridate mustard: with hoary sharp-pointed leaves shaped like an arrow-head; and only one feed in each cell. It is biennial, and grows in fields and open clayie grounds.
The feeds of these plants have an acrid biting taste, approaching to that of the common mustard; with which they agree nearly in their pharmaceutic properties, their pungent matter being totally extracted by water, only partially by rectified spirit, and being elevated by water in distillation. They have, joined to their acrimony, an unpleasant flavour, somewhat of the garlick or onion kind; and this they give out to spirituous as well as watery menstrua. They are rarely made use of any otherwise than as ingredients in the compositions whose names they bear: though some recommend them in different disorders, preferably to the common mustard.