straws and other substances to receive the flowing juice, the manna becomes much improved: Houel, who tasted the manna when flowing from the tree, found it much bitterer than in its concrete state; this bitterness he attributes to the aqueous part, which is then very abundant, of course the manna is meliorated by all the circumstances which promote evaporation. According to Lewis," the best manna is in oblong pieces, or flakes, moderately dry, friable, very light, of a whitish or pale yellow colour, and in some degree transparent: the inferior kinds are moist, unctuous, and brown. Manna liquifies in moist air, dissolves readily in water, aud, by the assistance of heat, in rectified spirit. On inspissating the watery solution, the manna is recovered of a much darker colour than at first. From the saturated spirituous solution, great part of it separates as the liquor cools, concreting into a flaky mass, of a snowy whiteness, and a very grateful sweetness."

Manna is well known as a gentle purgative, so mild in its operation, that it may be given with safety to children and pregnant women; in some constitutions however it produces troublesome flatulencies, and therefore requires the addition of a suitable aromatic, especially when given to an adult, where a large dose is necessary; it is therefore usually actuated by some other cathartic of a more powerful kind. The efficacy of manna is said, by Vallisnieri, to be much promoted by cassia fistularis, a mixture of the two purging more than both of them separately; it is therefore very properly an ingredient in the electuarium e cassia.

[Woodville. Cullen. Hort. Kew.

SECTION. II

Senna-Tree.

Cassia Senna.-LINN.

CASSIA in the Linnæan system is a voluminous genus, comprehending not fewer than fifty-four or fifty-six species; of these there are two that furnish useful materials in medicine. C. senna, which belongs to the present section, and C.Fistula, which will be described in the next.

The root of this plant is annual: the stalk is strong, smooth, branched, erect, and rises about two feet in height: the leaves stand

pulæ each leaf is composed of several pairs of oval or elliptical point. ed nerved sessile pinnæ, of a yellowish green colour: the flowers are yellow, and produced successively in long axillary spikes: the calyx consist of five leafits, which are narrow, obtuse, concave, unequal, and deciduous: the corolla is composed of five petals, which are roundish, concave, entire, and of unequal size: the filaments are ten, of which the three undermost are longer than the others, and fur. nished with large beaked curved antheræ; the germen stands upon a short pedicle, and is long, compressed, and supplied with a short style, which is turned inwards, and terminated by an obtuse stigma: the seeds are brown, roundish, flat, and produced iu a short compressed curved pod, divided by transverse partitions. The flowers appear in July and August.

Senna is a native of Egypt: it also grows in some parts of Arabia, especially about Mocha; but as Alexandria has ever been the great mart from which it has been exported into Europe, it has long been distinguished by the name of Alexandria Senna, or Sena.-Mons. Blondel, who was French Consul at several sea ports of the Levant, informs us, that the true senna grows only in the woods of Ethiopia and in Arabia; for that the seuna, which was brought from Saide and Tripoli was carried there by the caravans, and the negative testimony of Alpinus, who in his Lib. de plantis Ægypti does not notice senna, may seem to strengthen this opinion. But as Hasselquist found this plant growing spontaneously in Upper Egypt, the assertion of Mr. Blondel is not to be implicitly received.

The Senua Italica, or blunt-leaved senna, is a variety of the Alexandrian species, which by its cultivation in the south of France, (Provence) has been found to assume this change; it is less purga. tive than the pointed-leaved senna, and is therefore to be given in larger doses; it was employed as a cathartic by Dr. Wright at Ja. maica, where it grows on the sand banks near the sea.

Senna appears to have been cultivated in England in the time of Parkinson (1640); and Miller tells us, that by keeping these plants in a hot-bed all the summer, he frequently had them in flower, but adds, it is very rarely that they perfect their seeds in England. There can be little doubt however but that some of the British possessions may be found well enough adapted to the growth of this ve getable, and that the patriotic views of the Society for encouraging

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 under. stood; but it is observed by Dr. Cullen, that "when senna was infused in the infusum amarum, a less quantity of the senna was necessary for the dose than the simple infusions of it." The same au thor has remarked, "that as seuna seldom operates without much griping, its frequent use is a proof how much most part of practi tioners 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 bran ches 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 pinne, which are ovate, pointed, undulated, nerved, of a pale green colour, and stand upou shortish footstalks; the flowers are large, yellow, and placed in spikes upon long pe duncles 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 mauner described in the pharmacopoeias.

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 undis solved 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, aud 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.