Arts, &c. which has offered a reward to those who succeed in the attempt, will be ultimately accomplished.

The leaves of senna which are imported here for medicinal use, have a rather disagreeable smell, and a subacrid bitterish nauseous taste they give out their virtue both to watery and spirituous menstrua, communicating to water and proof spirit a brownish colour, more or less deep according to the proportions; to rectified spirit a fine green.

Senna, which is in common use as a purgative, was first known to the Arabian physicians, Serapion and Mesue; and the first of the Greeks by whom it is noticed is Actuarius, who does not mention the leaves, but speaks of the fruit. Mesue likewise seems to prefer the pod to the leaves, as being a more efficacious cathartic, but the fact is contrary, for it purges less powerfully than the leaf, though it has the advantage of seldom griping the bowels, and of being without that nauseous bitterness which the leaves are known to possess. How bitterness aids the operation of senna is not easily to be understood; but it is observed by Dr. Cullen, that "when senna was infused in the infusum amarum, a less quantity of the senna was ne. cessary for the dose than the simple infusions of it." The same author has remarked, "that as senna seldom operates without much griping, its frequent use is a proof how much most part of practitioners are guided by imitation and habit. Senna, however, when infused in a large proportion of water, as a dram of the leaves to four ounces of water, rarely occasions much pain of the bowels, and to those who do not object to the bulkiness of the dose, may be found to answer all the purposes of a common cathartic. For covering the taste of senna, Dr. Cullen recommends coriander seeds; but for preventing its griping, he thinks the warmer aromatics, as cardamoms or ginger, would be more effectual. The formulæ given of the senna by the Colleges, are those of an infusion, a powder, a tincture, and an electuary. Its dose in substance is from a scruple to a dram. [Lewis. Cullen. Woodville.

SECTION III.

Purgative Cassia.

Cassia Fistula.-LINN.

We have observed in the preceding section that this is only one of the numerous species belonging to the genus Cassia. This tree frequently rises forty feet in height, producing many spreading branches towards the top, and covered with brownish bark, intersected with many cracks and furrows: the leaves are pinnated, composed of four to six pairs of pinnæ, which are ovate, pointed, undulated, nerved, of a pale green colour, and stand upon shortish footstalks; the flowers are large, yellow, and placed in spikes upon long peduncles: the calyx consists of five oblong blunt greenish crenulated leaves: the corollæ is divided into five petals, which are unequal, spreading, and undulated: the filaments are ten; of these the three undermost are very long, and curled inwards; the remaining seven exhibit only the large antheræ, which are all rostrated, or open at the end like a bird's beak: the germen is round, curved inwardly, without any apparent style, and terminated by a simple stigma: the fruit is a cylindrical pendulous pod, from one to two feet in length; at first soft and green, afterwards it becomes brown, and lastly black and shining, divided transversely into numerous cells, in each of which is contained a hard round compressed seed, surrounded with a black pulpy matter. The flowers appear in June and July.

This tree, which is a native of both the Indies, and of Egypt, was first cultivated in England by Mr. Philip Miller in 1731. The pods of the East India Cassia are of less diameter, smoother, and afford a blacker, sweeter, and more grateful pulp than those which are brought from the West Indies, South America, or Egypt, and are universally preferred. In Egypt it is the practice to pluck the Cassia pods before they arrive at a state of maturity, and to place them in a house, from which the external air is excluded as much as possible: the pods are then laid in strata of half a foot in depth, between which palm leaves are interposed; the two following days the whole is sprinkled with water, in order to promote its fermentation: and the fruit is suffered to remain in this situation forty days, when it is sufficiently prepared for keeping.

Those pods, or canes, which are the heaviest, and in which the seeds do not rattle on being shaken, are commonly the best, and contain the most pulp, which is the part medicinally employed, and to be obtained in the manner described in the pharmacopœias.

The best pulp is of a bright shining black colour, and of a sweet taste, with a slight degree of acidity. "It dissolves both in water and in rectified spirit; readily in the former, slowly and difficultly in the latter, and not totally in either: the part which remains undissolved appears to be of little or no activity."

We are told by C. Bauhin, that some have supposed the Siliqua Ægyptiaca of Theophrastus to be our Cassia Fistula; but there seems no evidence of its being known to the ancient Greeks; so that it is with more probability thought that the use of this, as well as of senna, was first discovered by the Arabian physicians.

The pulp of cassia has been long used as a laxative medicine, and being gentle in its operation, and seldom occasioning griping or uneasiness of the bowels, has been thought well adapted to children, and to delicate or pregnant women. Adults, however, find it of little effect, unless taken in a very large dose, as an ounce or more, and therefore to them this pulp is rarely given alone, but usually conjoined with some of the brisker purgatives. It has been observed by Vallisnieri, that its purgative quality is remarkably promoted by manna; but this effect was never discovered in the trials made by Dr. Cullen, in whose opinion the cassia pulp is much of the same nature as the fructus acido dulces; and he says, "that it would certainly be proper for our country apothecaries to know, that the pulp of prunes might be employed in the place of the more expen sive and precarious cassia."

By the use of cassia, it has been remarked, that the urine becomes of a green or blackish colour; but Bergius relates, that a young man took an ounce three successive mornings, without producing the least change in the colour of his urine.

The officinal preparation of this drug is the electuarium e cassia : it is also an ingredient in the electuarium e senna, or e. lenitivum. [Sennert. Boerhaave. Gmelin. Woodville.

SECTION IV.

Liquorice Plant.

Glycyrrhiza Glabra.-LINN.

The genus of glycyrrhiza has four species. The glabrous, or that which produces the liquorice of the shops, has a long, thick, creeping root, striking several feet deep into the ground; upright, firm, herbaceous, stalks annual, and three or four feet high, with winged leaves of four or five pairs of oval lobes, terminated by an odd one; and from the axillas erect spikes of pale blue; flowers in July or August, succeeded by short smooth pods.

Liquorice is a native of the South of Europe: it appears to have been cultivated in Britain in the time of Turner*. The chief places at which it has long been propagated for sale, are Pontefract in Yorkshire, Worksop in Nottinghamshire, and Godalming in Surry; but it is now planted by many gardeners in the vicinity of London, by whom the metropolis is supplied with the roots, which, after three years growth, are dug up for use, and are found to be in no respects inferior for medicinal purposes to those produced in their native cli

mate.

Liquorice root, lightly boiled in a little water, gives out nearly all its sweetness: the decoction, pressed through a strainer, and inspissated with a gentle heat till it will no longer stick to the fingers, affords a better extract than that brought from abroad, and its quantity amounts to near half the weight of the root+. Rectified spirit takes up the sweet matter of the liquorice equally with water; and as it dissolves much less of the insipid mucilaginous substance of the root, the spirituous tinctures and extracts are proportionably sweeter than the watery t.

This root contains a great quantity of saccharine matter §, joined with some proportion of mucilage; and hence has a viscid sweet taste.

* Vide Tourn. Herb. part 2, fol. 12. published in 1562.

+ If the liquorice be long boiled, its sweetness is greatly impaired, and the preparation contracts an ungrateful bitterness and black colour.

Lewis, M. M.

This matter, according to Lewis, differs from that of other vegetables, "in being far less disposed to run into fermentation." L. c.

From the time of Theophrastus* it has been a received opinion that it very powerfully extinguishes thirst: this, if true, is the more remarkable, as sweet substances in general have a contrary effect+. It is in common use as a pectoral or emollient in catarrhal defluxions on the breast, coughs, hoarsenesses, &c. " Infusions or extracts made from it afford likewise very commodious vehicles or intermedia for the exhibition of other medicines: the liquorice taste concealing that of unpalatable drugs more effectually than syrups or any of the sweets of the saccharine kind t."

Theophrast. Plin. Cullen. Woodville.

SECTION V.

Tamarind Tree.

Tamarindus Indica.-LINN.

The Indian tamarind is the only known species of this genus. The tree rises to a great height, sending off numerous large branches, which spread to a considerable extent, and have a beautiful appearance: the trunk is erect, thick, and covered with rough bark of a greyish or ash-colour: the leaves are pinnated, alternate, consisting of several parts (about 14) of small pinnæ, which are opposite, oblong, obtuse, entire, smooth, of a yellowish green colour, and stand upon very short footstalks: the flowers approach to the papilionaceous kind, and are produced in racemi or lateral clusters: the calyx consists of four deciduous leaves, which are patent or reflexed, oblong, or rather ovate, entire, smooth, nearly equal in size, and strawcoloured or yellowish: the petals are three, ovate, concave, acute, indented, and plaited at the edges, about the length of the calyx, and of a yellowish colour, beautifully variegated with red veins: the

• Hence it was named ador, and the root directed to be chewed in dropsies and other disorders where great thirst prevailed. Vide Theoph. L. 9. cap. 13. Also noticed by Pliny, Lib. 22. c. 9.

† Dr. Cullen says, “to explain this, I observe that in the sweet of liquorice, separated from the root, I do not find that it quenches thirst more than other sweets; and I take the mistaken notion to have arisen from this, that if a piece of the root is chewed till the whole of the sweetness is extracted, that further chewing brings out the acid and bitterish matter, which stimulates the mouth and fauces, so as to produce an excretion of fluid, and thereby takes off the thirst which the sweetness had produced." M. M. vol. ii. p. 407.

Lewis, 1. c.