046. Rheum palmatum. Officinal rhubarb.
Synonyma. Rhabarbarum. Pharm. Lond. & Edinb.
Rhabarbarum verum Med. Hope, l. inf. cit.
Rheum palmatum; fol. palmatis acuminatis. Lin. Spec. Plant. p. 281. Conf. cel. Hope descriptionem in Act. Philosoph. Loudin. vol. 55. c. l. Linnaei jun. in Pl. rarior. hort. Upsal. fasc. 1. item cl. Sandemani in Diss. de Rheo palmato; et Milleri in ejus Illustr. Syst. Sex.
Class Enneandria. Ord. Trigynia. Lin. Gen. Plant. 506.
Ess. Gen. Ch. Cal. o. Cor. 6-fida, persistens. Sem. 1, triquetrum.
Spec. Char. R. foliis palmatis acuminatis scabriusculis: sinu baseos dilatato, petiolis supra obsolete fulcatis margin e rotundatis. Aiton. Hort. Kew.
The root is perennial, thick, of an oval shape, and sends off long tapering branches; externally it is brown, and internally of a deep yellow colour: the stalk is erect, round, hollow, jointed, sheathed, slightly scored, branched towards the top, and rises to the height of six or eight feet: the radical leaves are numerous, large, rough, of a roundish figure, and deeply cut into lobes, and irregularly pointed segments, and stand upon long smooth round footstalks: the leaves which proceed from the stalk are placed at the joints, which they supply with membranous sheathes, and are successively smaller towards the upper part of the stem: the flowers terminate the branches, which they surround in numerous clusters, forming a kind of spike, and appear in April and May: the corolla divides into six obtuse segments, which are of a greenish white colour, and alternately smaller: the calyx is wanting: the filaments are nine, slender, about the length of the corolla, and furnished with oblong double antherae: the style is very short, and terminated by three reflected stigmata: the germen becomes a triangular seed, with membranous margins of a reddish colour. It is a native of Tartary in Asia.
It was not until the year 1732 that naturalists became acquainted with any plant which seemed to afford the Rhabarbarum Officinale, [The Rheum Rhaponticum of Linnaeus, or Rhaponticum folia Lapathi majoris glabra of C. Bauhin, is generally supposed to be the Rhabarbarum of the ancients; "Alpinus aliique putant esse (greek) vel (greek) veterum, cujus radicem usurparunt. (Vide Dioscorid. Mat. Med. lib. 3. cap. 2.) Ipse Alpines libi circa annum 1610, stirpem, ex Thracia procuravit, et haec Patavio Venetiam primo, dein inde in Angliam ad Parkinsonium (Theat. Bot. p. 157.) pervenit." Murray Ap. Med. vol. iv. 354. It is well known that the ancient rhubarb had not the purgative power of the modern.] when some plants, received from Russia by Jussieu at Paris, and Rand at Chelsea, [Seeds of this species were also sent to Miller from Boerhaave at Leyden, by the title of "Rhabarbarum verum Chinense." See his Gard. Dict.] were said to supply this important desideratum, and as such were adopted by Linnaeus, in his first edition of the Species Plantarum, under the name of Rheum Rhabarbarum. This however was not very generally received as the genuine Rhubarb plant; and with a view to ascertain this matter more completely, Kauw Boerhaave procured from a Tartarian rhubarb merchant the seeds of those plants, whose roots he annually sold, and which were admitted at Petersborough to be the true rhubarb: these seeds were soon propagated, and were discovered by De Gorter to produce two distinct species, viz. the R. Rhabarbarum of Linnaeus, or as it has since been called R. undulatum, and another species, a specimen of which was presented to Linnaeus, who declared it to be a new one, and was first mentioned in the second edition of the Sp. Plantarum in 1762, by the name of R. palmatum, (the plant we have figured). Previous to this time, De Gorter had repeatedly sent its seeds to Linnaeus, [See the letters between De Gorter and Linnaeus, by Nozeman, in Verhandelingen van het Genootschap to Rotterdam, vol. i. p. 455, and cited by Murray.] but the young plants which they produced constantly perished; at length he obtained the fresh root, which succeeded very well at Upsal, and afterwards enabled the younger Linnaeus to describe this plant [Vide Plant, rarior. hort. Upsal. fasc. 1.] ann. 1767. But two years antecedent to this, Dr. Hope's account of the Rheum palmatum, as it grew in the botanic garden near Edinburgh, had been read before the Royal Society at London; and of the great estimation in which the plant was held by him, we have the following proof: "From the perfect similarity of this root with the best foreign rhubarb in taste, smell, colour, and purgative qualities, we cannot doubt of our being at last possessed of the plant which produces the true rhubarb, and may reasonably entertain the agreeable expectations of its proving a very important acquisition to Britain." [See Philosoph. Trans. for the year 1765.] But from the relation we have given, it appears that the seeds of both R. undulatum and R. palmatum, were transmitted to Petersborough, as those of the true Rhubarb: we are therefore to conclude, that the former species has an equal claim to this importance with the latter; [Bergius says, "Rheum palmatum producit Rhabarbarum in officinis Sibiricum appellatum; certe e seminibus a Bucharis e montosis Tibeti in Russiam apportatis, & postea satis hocce Rheum palmatum enatum est." (Vide Pallas Reise, &c. vol. 3. p. 157) "Rhabarbarum vero Chinense ex alia specie Rhei desumptum esse videtur." (Vide Georgi Reife, &c. vol. i. p. 211.)] and from further enquiries made in Russia, there is the best authority for believing that the R. compactum also affords this very useful drug. [The roots of the Rheum Palmatum were considered to be the best rhubarb, " donec viri celeberrimi, Pallas et Georgi, qvi nuperrime in rem naturalem Russiae itineribus suis inquisiverunt, scrupulos novos excitarent. Nam percontanti ill. Pallas Buchari, folia Rhei palmati sibi ignota declararunt, describentes contra ea folia veri Rhabarbari rotunda et in margine paucis modo incisionibus notata; unde concludit iste Rheum compactum potius suisse intellectum. Huc pertinent supra ex cl. Georgi itinerario dicta (V. p. 360) de Cosacco quodam, qui Rheum undulatum pro vera specie significavit. Uterque etiam arbitratur, Rheum undulatum in montibus australionbus apertioribus et siccioribus, quales Tibetici sunt, praestantiorem posse radicem ferre quam montes frigidi et humidi Sibiriae." Murray I. c. Pallas Reise, vol. 3. p. 156. Georgi Reife, vol. i. p 210. The seeds of the compactum were sent to Miller "from Petersborough, for the true Tartarian rhubarb, and were gathered from the plants growing on the spot, where the rhubarb was taken up; and upon trial of the roots, they are found to be as good as the foreign rhubarb." See his Dict. 6th edition.] The seeds of the Rheum Palmatum were first introduced into Britain in 1762, [In the Hort. Kew. this plant is said to have been first cultivated in England by Miller in 1768.] by Dr. Mounsey, (who sent them from Russia) and were supposed to be a part of those already mentioned; and since their prosperous cultivation by the late Professor of Botany at Edinburgh, the propagation of this plant has been gradually extended to most of our English gardens, and with a degree of success which promises in time to supercede the importation of the foreign root. [The Society for Encouragement of Arts, Manufactures, and Commerce, has laudably contributed to this national object, of which their Transactions published bear sufficient evidence.]
Two sorts of rhubarb roots are usually imported into this country for medical use, viz. The Chinese, [Colitur hoc a Chinensibus, praecipue in provincia Xensi sub nomine Taihoang. Bergius, M. M. p. 332.] and the Turkey rhubarb; ["Olim, quum commercium in orientalibus regionibus per Natoliam fieret, Rhabarbarum ex portibus Turcicis ad Europaeas transferebatur, unde nomen Rhabarbari Turcici." Murray, l. c. Mr. Bell (in his Travels from St. Petersburg to divers parts of Asia) says, that the best rhubarb grows plentifully on a long chain of mountains in Tartary, which extend from Selin to the lake Koko-nor near Tibet. At a proper age the roots are taken up, which, according to Pallas, is in April or May; but in Bell's account, this is said to be done in the autumn: they are then to be cleaned, the smaller branches cut off, and the larger roots divided into pieces of a proper size; after this they are perforated, and suspended to dry either upon the neighbouring trees, or in tents, or as some have reported, to the horns of sheep. The proper exsiccation of this root is certainly attended with considerable difficulty, and the cultivators of rhubarb in this country have not yet agreed in what mode this is to be best accomplished. The recent root in this process, according to the experiment of Sir William Fordyce, loses nearly nine-tenths of its weight." See Trans. of the Society for Encouragement of Arts, &c.] the first is in oblong pieces, flattish on one side, and convex on the other; compact, hard, heavy, internally of a dull red colour, variegated with yellow and white, and when recently powdered appears yellow, but on being kept becomes gradually redder. The second is the most valuable, and is brought to us in roundish pieces, with a large hole through the middle of each; it is more soft and friable than the former sort, and exhibits, when broken, many streaks of a bright red colour. "The marks of the goodness of rhubarb are, the liveliness of its colour when cut; its being firm and solid, but not flinty or hard; its being easily pulverable, and appearing when powdered of a fine bright yellow colour; its imparting to the spittle, on being chewed, a deep saffron tinge, and not proving slimy or mucilaginous in the mouth; its taste is subacrid, bitterish, and somewhat styptic; the smell lightly aromatic."
The purgative qualities of rhubarb are extracted more perfectly by water than by rectified spirit: the root remaining after the action of water is almost if not wholly inactive; whereas after repeated digestion in spirit, it proves still very considerably purgative. The virtue of the watery infusion, on being inspissated by a gentle heat, is so much diminished, that a dram of the extract is said to have scarcely any greater effect than a scruple of the root in substance; the spirituous tincture loses less; half a dram of this extract proving moderately purgative. "The qualities of this root are that of a gentle purgative, and so gentle that it is often inconvenient by reason of the bulk of the dose required, which in adults must be from half a dram to a dram. When given in a large dose, it will occasion some griping, as other purgatives do; but it is hardly ever heating to the system, or shews the other effects of the more drastic purgatives. The purgative quality is accompanied with a bitterness, which is often useful in restoring the tone of the stomach when it has been lost; and for the most part its bitterness makes it fit better on the stomach than many other purgatives do. Its operation joins well with that of neutral laxatives; and both together operate in a lesser dose than either of them would do singly. Some degree of stipticity is always evident in this medicine, and as this quality acts when that of the purgative has ceased, so in cases of diarrhoea, when any evacuation is proper, rhubarb has been considered as the most proper means to be employed. I must however remark here, that in many cases of diarrhoea, no further evacuation than what is occasioned by the disease is necessary or proper.—The use of rhubarb in substance for keeping the belly regular, for which it is frequently employed, is by no means proper, as the astringent quality is ready to undo what the purgative had done; but I have found that the purpose mentioned may be obtained by it, if the rhubarb is chewed in the mouth, and no more is swallowed than what the saliva has dissolved. And I must remark in this way employed it is very useful to dyseptic persons. Analagous to this, is the use of rhubarb in a solution, in which it appears to me, that the astringent quality is not so largely extracted as to operate so powerfully as when the rhubarb was employed in substance." [We have transcribed this account from Dr. Cullen, who has paid more than usual attention to this article. See Mat. Med, vol. 2. p. 529.]
The officinal preparations of this drug are, a watery and a vinous infusion, a simple and a compound tincture. It is also an ingredient in different compositions, as the Elixir ex aloe et rheo, pilulae stomachicae, and some others.