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Professor Willdenow, who established the genus to which the subject of the present article belongs, first separated it from the Linnean Mimosa, by the characters of the fruit. Under Mimosa, he leaves such species as have a lomentum, or legume, separating into single-seeded joints. Of these he defined thirty-two, but the list now exceeds seventy; and to many of them being sensitive, the name Mimosa is very appropriate. Willdenow enumerated a hundred-and-two species of Acacia, but since his time, the discoveries of modern travellers have augmented the catalogue, so that upwards of three hundred now are known. They are all shrubby, perennial plants, with the exception of two or three species, which are herbaceous.

The Acacia Catechu, called in the province of Bahar, coira or caira, grows in great abundance in most of the mountainous districts of Hindustan. It is a large shrub or tree, fifteen or twenty feet high, covered with a thick, scabrous, ferruginous bark, which is very red within, remarkably astringent, and somewhat bitter. The branches are round, spreading irregularly, and downy when young; the older ones beset with numerous pairs of small recurved spines, originating in the stipules. The leaves are placed alternately on the younger branches, and are composed of from fifteen to thirty pair of pinnae, about two inches long, each having numerous linear leaflets, (often forty pair,) hardly a quarter of an inch long, covered with short hairs, and of a green colour. The common petiole is sometimes furnished with a few recurved prickles, and a small gland is placed between the bases of each pair of the pinnae. The flowers are hermaphrodite and male; axillary, on slender cylindrical spikes, three or four inches long, hairy, stalked, and of a pale yellow colour. The calyx is tubular, hairy, and 5-toothed; the corolla of one piece, whitish, divided into five segments, and twice the length of the calyx. The filaments are numerous, crowned with roundish anthers, and united at the base with the germen, which is oval, supporting a slender style, and terminated by a simple stigma. The fruit is a straight, smooth, pointed legume, or pod, three or four inches long, and less than one broad, containing six or eight roundish seeds.

Catechu was formerly supposed to be an earth, found in Japan; and the name Terra Japonica, by which it is still designated occasionally, tends to perpetuate the error. Mr. Kerr, assistant surgeon to the Civil Hospital in Bengal, was the first to describe the catechu tree, in Vol V.of "Medical Observations and Enquiries," which contains also a very correct figure. He says, that it is one of the most common trees to be met with in the uncultivated mountains of Rotas, and Pallamow, which are districts of Hindustan, in the province of Bahar, west ward of Bengal; and is frequent in many other parts of that country, in various soils. The following is the mode of preparing the Extract, as described by that gentleman:—

"After felling the trees, the manufacturer carefully cuts off all the exterior white part of the wood. The interior coloured wood is cut into chips, with which he fills a narrow-mouthed unglazed earthen pot, pouring water upon them until he sees it among the upper chips: when this is half evaporated by boiling, the decoction, without straining, is poured into a flat earthen pot, and boiled to one third part; this is set in a cool place for one day, and afterwards evaporated by heat of the sun, stirring it several times in the day; when it is reduced to a considerable thickness, it is spread upon a mat or cloth which has previously been covered with the ashes of cow dung; this mass is divided into square or quadrangular pieces by a string, and completely dried by turning them frequently in the sun, until they are fit for sale.

"This extract is called cutt by the natives, by the English cutch, by authors terra Japonica, catechu, cadtchu, cashow, cachou, cailchu, caitjoe, cachore, kaath, cate, fyc. In making the extract, the pale-brown wood is preferred, as it produces the fine whitish extract; the darker the wood is, the blacker the extract, and of less value. They are very careful in drying their pots upon the fire before they are used; but very negligent in cutting their chips upon the ground, and not straining the decoction; by which, and the dirty ashes they use, there must be a considerable quantity of earth in the extract, besides what avarice may prompt them to put into it. This the learned have proved from their laborious chemical decompositions. The extract thus prepared, is bought from the manufacturer for twelve or fifteen shillings the eighty pounds weight. 1 could never learn that the terra Japonica was produced from the areca or betelnut; nor is it indeed credible that it should, notwithstanding that this is the general and received opinion, for the betel-nut is scarce ever so low in price as the terra Japonica, and was it to be extracted from thence, the price would be twenty times dearer than the present sales. Where the areca nut is in great plenty, they may perhaps join some of the fruit in making the extract, to answer a double purpose, for the most trequent use of both is in chewing them together as Europeans do tobacco; to these two substances they add a little shell lime, and a leaf called pauw. Here I am obliged to have recourse to the natives, whom from experience I have found to be very fallacious, therefore I will not answer for their veracity.

"The extract is much used in dyeing and painting chintz, and other cloths; combined with vitriolic salts, a black colour is produced; mixed with oil, they paint the beams and walls of houses to preserve them, and to defend them from the destructive white ants; it is so retimes mixed with their wall plaister.

"The black physicians of this country divide the diseases of mankind, as well as their medicines, into hot and cold; to the cold disease they oppose a hot medicine, and to the hot disease a cooling medicine, among which last, this Extract is supposed to be very powerful.

"The extract is a principal ingredient in one of their ointments of great repute, composed of blue vitriol four drachms, Japan earth four ounces, alum nine drachms, white resin four ounces; these are reduced to a fine powder, and mixed with the hand, adding olive oil ten ounces, and water sufficient to bring the mass to the proper consistence of an ointment. This ointment is used in every sore, from a fresh wound. A gentleman (Mr. Robert Hunter, Surgeon to the Patna Factory) of great practice, told me, he used this ointment with success beyond expectation; and he remarks, that whether it is owing to the laxity of the solids in this hot climate, or to some other cause, he is clearly of opinion, that our greasy ointments have not the desired effect. Certain it is they avoid that empyreuma which our ointments often receive in boiling which cannot be a promising application to a tender sore. As to the virtues of this Extract in European practice, I must be silent; they are already better described than I can pretend to do."

Qualities And Chemical Properties.—There are two kinds of this extract; one is sent from Bombay, the other from Bengal; but they differ from each other more in their external appearance, than in their chemical composition. The extract from Bombay is of a uniform texture, and of a red brown tint; its specific gravity being generally about 1.39. The extract from Bengal is more friable, and less consistent; its colour is like that of chocolate externally, but when broken its fracture presents chocolate and red-brown streaks. Its specific gravity is about 1.28. Their tastes are precisely similar, being astringent, but leaving in the mouth a sensation of sweetness. They do not deliquesce, or apparently change, by exposure to the air. Solutions copiously precipitate gelatine, and speedily tan skins. The strongest infusions of the two kinds do not differ sensibly in their nature or composition. Their colour is deep red-brown, and they communicate this tinge to paper; they slightly redden litmus paper; their taste is highly astringent, and they have no perceptible smell. The strongest infusions act upon the acids, in a manner analogous to the infusion of galls. Sulphuric and muriatic acids precipitate them. With strong nitrous acid they effervesce, and lose their power of precipitating solutions of isinglass and the salts of iron. The pure alkalies enter into union with their tannin, so as to prevent it from being acted upon by gelatine. Solutions of lime of strontia, and of barytes, poured into the infusions of catechu, produce copious precipitates. If carbonate of magnesia be added to the infusion, it loses its power of precipitating gelatine. The carbonates of potash, of soda, and of ammonia, also deprived them of their power of acting upon gelatine: though this power is restored by an acid. Solution of muriate of tin acts upon the infusion of catechu, in a manner similar to that in which it acts upon the infusion of galls. Both kinds of catechu are almost wholly soluble in large quantities of water; and to form a complete solution, about eighteen ounces of water, at 52°, are required to a hundred grains of extract. A considerable portion of both kinds of catechu is soluble in alcohol; but, after the action of the alcohol upon it, a substance remains, of a gelatinous appearance, and a light brown colour, which is soluble in water, and is analogous in its properties to gum or mucilage.

The peculiar extractive matter of the catechu, is much less soluble in water than the tanning principle; and when a small quantity of water is used to a large quantity of catechu, the quantity of tannin taken up is much greater than that of the extractive matter. The extractive matter is much more soluble in warm water than in cold; and when saturated, solutions of catechu are made in boiling water, a considerable quantity of extractive matter, in its pure state, falls down as the liquor cools. An aqueous solution of the extractive matter, when mixed with solutions of nitrate of alumine, and of muriate of tin, becomes slightly turbid. Nitrate of lead gives a dense brown precipitate. It is not precipitated by the mineral acids. Two hundred grains of Bombay Catechu, afforded 109 of tannin, 68 of extractive matter, 13 of mucilage, and 10 of sand, calcareous earth, and other impurities. The variety from Bengal gave, by a similar analysis, 97 of tannin, 73 of extractive matter, 16 of mucilage, and 14 of residual matter, and sand, with a small quantity of calcareous and aluminous earth, in two hundred grains.

Medical Properties And Uses.—Catechu is largely employed in the East, medicinally; but especially when used with the betel-nut, for chewing, a practice almost universal over the Indian continent.

In this country it is extensively employed for all those disorders in which a mild, unirritating, powerful astringent is required; such as chronic diarrhoea and dysentery; hoemorrhoids, &c, and the Bombay catechu, as containing the greatest portion of tannin, is that which is best adapted for medicinal use. It is one of the most valuable medicines of the class, and may be advantageously used in all cases where we wish to restrain immoderate discharges, especially when not attended by inflammatory action, or produced by congestion. With this indication, it is usually combined with the bitter tonic and aromatic barks. It is also used in the form of troches, mixed with gum-arabic and sugar, to dissolve slowly in the mouth; and in this form it often much assists the clearness of the voice in persons that have occasion to speak long in public. As a topical astringent it is used in scorbutic affections of the gums, and aphthous ulcerations of the mouth and fauces. Dr. Thompson has found the slow solution of a small piece in the mouth, "a certain remedy for the troublesome cough induced by a relaxed uvula, hanging into, and irritating the glottis."

Dose.—Erom gr. x. to 3L of the powder; or, 3i. to 3iij. of the Tincture

Off Prep.—lnfusum Catechu, L. E. Tinctura Catechu, L. E. Electuarium Catechu compositum, E. D.

"The distilled water of the leaves of the Acacia contains prussic acid. The water has a strong smell of bitter almonds, and eight ounces of it, precipitated by nitrate of silver, yielded 4.15 grains of cyanide. The dried leaves gave no prussic acid on distillation."—[Dr. Taylor on Poisons, p. 719.]

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