This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Rocket: a plant with smooth oblong narrow leaves deeply jagged about the edges, bearing on the tops of the stalks numerous tetrapetalous flowers, which are followed by angular pods, full of small roundish seeds flatted on one side. It is annual.
1. Eruca: eruca latifolia alba, sativa diofco-ridis C. B. Brassica Eruca Linn. Garden or Roman rocket, or rocket gentle: with leaves like those of turneps, but much smaller; and whitish flowers variegated with black streaks. It is a native of Switzerland, and cultivated among us in gardens.
2. Eruca silvestris: eruca sylvestris major lutea caule aspero C. B. Braffica Erucastrum Linn. Wild rocket: with leaves like those of dandelion, and yellow flowers; common on old walls, and among rubbish.
The leaves of both the rockets have an acrid taste like that of cresses, and a rank disagreeable smell: the roots are as acrid as the leaves: the seeds much more so, approaching to the pungency of mustard. The wild sort is, in all its parts, considerably more acrid than the garden, though the faculty of Paris allows both sorts to be taken indiscriminately. They are accounted good aperients and antiscorbutics, but are now rarely made use of on account of their ill flavour: to the aphrodisiac virtues, commonly ascribed to them, they appear to have no other title than the reft of the pungent simulating plants.
The active matter of the leaves is extracted by expression, by infusion in boiling water, and by digestion or maceration in rectified spirit; with this difference, that the infusions and tinctures retain the ill smell of the herb, which in exprossion is in great measure destroyed. On drying the herb itself, or infpiffating the juice of the watery or spirituous tinctures, the pungency, as well as the smell, is almost totally dissipated. In distillation with water, a very small quantity of a yellowish, very pungent, and very volatile, essential oil is obtained.
The pungency of the seeds is of a less volatile kind; not exhaling in exsiccation, and arising more difficultly with water in distillation: and though it appears to reside, as that of the leaves, in an essential oil, it is but partially extracted by rectified spirit. In these respects the seeds of rocket agree with those of mustard; to which they appear to be similar also, but inferiour, in medicinal virtue.