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the end, which, as the feed comes to maturity, tifually turn downwards and backwards. The fiofcules ftand on em- bryos, which finally ripen into feeds, winged with down. The fpccies of groundfel, enumerated by Mr. Tournefort, are thefe. I. The common fmall groundfel. 2. The taller groundfel with ragwort leaves. 3. The tall, iarge-leaved American groundfel. And 4, the American groundfel with bluifli purple flowers. 1'eurn. Inft. p. 456. The common groundfel, taken in a ftrong infufion, is an emetic. It is prefcribed in fmaller dofes in dropfies, jaun- dices, and hemorrhages. Externally it is ufed in ointments againft cutaneous foulncffes.
SENECTA anguium, the exuviae, or floughsof ferpents. The fnakes caft their whole fkin, and with it were fuppofed to caft off their age, and be born anew ; whence the name of thefe caft fkins. A decoction, or infufion of thefe, is recom- mended by medical writers againft pains of the ears and eyes ; and fome fuperftitious people recommend it to women, to tye about their waftes, to prevent mifcarriages, and about their thighs, in time of labour, to haften delivery.
SENEKA, rattlefnake-root. This is a root lately brought into ufe among us, and which feems to deferve very great regard. It is the root of a fpecies of polygala, or milkwort, diftin- guifhed by Gronovius, in his Flora Vifginica, under the name of the erect poly gala with a fimple ftalk, with oval leaves pointed at the end, and with an erect clufter of flow- ers. We generally call it the rattlefnake-root, and the French, from the place whence it comes, Seneka. See Pqlycala, The root is perennial, the thicknefs of it is generally about
' that of a man's little finger. It is four or five inches, or more, in length, and is varioufly contorted and twifted, and divides into many branches, furnifhed with finall fibres, and with a membranaceous rim" running all along it. It is ycllowifti on the outfidc, and white within ; very acrid, and fomewhat bitter to the tafte, and has fomewhat of an aromatic flavour. From this root arife numerous ftalks, all fimple, and without branches ; fome lie on the ground, others ftand erect. Thefe are ten or twelve inches high, when full grown. The leaves ftand alternately on the ftalks, and the flowers are white, and perfectly like thofe of our own kinds of poly gala.
Dr. Tennent, who brought over avaft quantity of this root from America fome years ago, and took great pains to in- troduce it into practice, praifes it very largely as a diuretic, a diaphoretic, and an alexipharmic, and a very powerful attenuant and refolvent. He fays it will fometimes vomit and purge.
The Indians firft taught the ufe of it to the Europeans : thty efteem it a fovercign remedy againft the bite of the rattlefnake ; and Dr. Tennent aflures us that he faw two perfons, who had been bitten by this creature in the month of July, when its poifon is moft fatal, perfectly reftored to health by it.
He afterwards gave it in plcurifies and peripneomonies with great fuccefs, and in all other cafes where the blood is in- Jpiflatcd. If the firft dofes of it provoke a vomiting, it is not at all the worfe, except in cafes in which the patient is Very weak ; and in fuch this effect is eafily prevented, by giving fame of the teftaceous powders with it. In pleurifies it is beft to take away ten ounces of blood, be- fore the entering on the life of the medicine ; in other cafes no precaution is required, but it is to be given in powder, or tincture, in white wine, and the ordinary drink, during the ufe of it, fhould he marftimallow tea. Gronov. Flora Virgin, p. 80. Geoffrey, Mat. Med. Vol. 2. p. 140. Tcn- nenfs Eflay on the Pleurify.
This medicine may be given either in powder or decoction ; but Dr. Tennent prefers the decoction, having obferved it to give relief fooner than the powder does. The dofeof the powder is thirty five grains, and he gives at once three fpoonfuls of the decoction, prepared by boiling three ounces of the' root bruifed in a quart of water to near the half. The dofe is repeated every fix hours. He is alfo fond of this root in the rheumatifm, dropfy, and gout, in which Iaft difeafe, he fays, he has given it with fuccefs. See his letter concerning the Seneka, or rattlefnake-root. MeiVrs. Lemery, Du Hamel, and Juflieu, vouch for the good effects of the Sencka-root in pleurifies, and other in- flammatory difeafes. Mem. de l'Acad. des Scienc. 1739.
SENEMEI, in zoology, the name of a fpecies of Bralilian lizard, more commonly known by the name iguana. See Iguana.
SENESCHALLO et marejhallo quod non tencant placita de li- bera tenements, a writ, directed to the fteward and marfhal of England, inhibiting them to take cognizance of an ac- tion in their court that concerns freehold. Reg. Orig. 185, 191. Blount, Cowel.
SENORIiE, in botany, a name by which fome authors have called the bonana-trec, or mufa frufiu brev'wre. Jonf. Dendr. P- 143*
SENSI I IVE (Cycl.)— Srksitivz fuid. Some have imagined a fenfitive fluid as the principle that preferves animals from corruption, and to which we owe our fenfation and motion. This animal fluid pafies in the proper nervous tubes to the
organs of motion, but is contained in the fibrous coifs of the nerves to become an organ of fenfation. This fenfitive fluid is, according to Mr. Le Cat, capable of thinking, and is fo modified by the ganglions, that what is lodged in each part, is capable of being imprefl'ed by the object proper to each organ. And from the doctrine concerning this animal fluid, he endeavours to account for moft operations, which are generally faid to depend on the foul. Med. Eft". Edinb. Abnd. Vol. 2. p. 481.
But all thefe attempts to account for fenfation and thought, from the properties of matter, feem to be very defperate undertakings, not to fay abfurd.
Sensitive plant. This is an herb fufficiently known to the world for its remarkable property of receding from the touch, and giving figns, as it were, of animal life. Phi- lofophers in general have, however, contented tbemfelves with admiring the fact, without giving thcmfelves any trou- ble about the caufe.
Mr. Hook indeed has made fome conjectures about it; but the greateft light, that has been given into the thing, is from the inquiries which Meffrs. Du Fay and Du Hamel, gen- tlemen of the Academy of Sciences at Paris, concerted to- gether, and afterwards made fcparately on different ihrubs, or at different times, that each might be able to correct the errors of the other.
The ftructureof the fenfitive plant is this. From the large Items, or main branches of the whole, there part off feveral other lefler ones, and from thefe there go off others ftill lefs, which by way of diftinction may be called the ribs of the leaves, as they ferve to fupport a number of leaves ar- ranged on each fide, and Handing on fhort pedicles in pairs, over againft one another. Several other plants have thefe fort of compound leaves, as the caflia, colutea, and the like ; and all thefe ftiut their leaves together at night, and open them again in the morning, in the fame manner as the fenfitive plant does. This periodical opening and (hutting of the leaves is therefore common to many plants, not pe- culiar to the fenfitive plant ; but the marvel in this is, that befide having this motion periodical and regular, it is to. be brought on at other times, and by accidents, there requiring no more than the touching the plant to make it clofe its leaves at any time of the day, which it foon- afterwards na- turally opens again. This is peculiar to this plant, and re- fembles the action of an animal which had been injured or frighted. A clofe obfervation alfo of the manner in which this is performed, will give many hints toward the finding its caufe. It is a very difficult tbjng to touch the leaf of a vigorous fenfitive plant fo lightly, as not to make it clofe. Its fenfation is extremely delicate, and its large rib or nerve, which runs along its middle, is as it were a hinge, on which the two halves of the leaf move when they turn up on bein<* touched, till they ftand erect, and by that means meet one another. The flighteft touch imaginable gives this motion to the fide of the leaf which is touched, which is commu- nicated immediately to the other fide, or half, and they move together ; and if the touch have been a very little rougher, the oppofite leaf on the fame rib receives the im- preflion, and clofes up in the fame manner with that which was actually touched.
Nor is this all ; for when the two fides of each of thefe leaves move upwards, the pedicle of each half moves up- wards at the fame time, and by this means they in fome meafure approach toward each other, and make the angles of their pedicles with the main rib, or ftalk of the compofit leaf, lefs than before ; and the total motion of each leaf is compofed of thefe two motions.
If the touch be ftill rougher, the whole arrangement of leaves on the fame rib feel its influence on each fide, and all clofe in the fame manner with the fingle pair in the pre- cedent inftance : and if the touch be yet ftronger than this, the rib itfelf feels it, and attempts to clofe in its way; moving itfelf upwards toward the branch from which it is produced, juft as the fingle pedicles of the leaves did toward it : and if the touch be yet more hard and rough, the very branches have the fenfation propagated to them, and apply tbemfelves to the main ftem, or trunk of the fhrub, as the fimple leaves did before to their ri,b, and that rib to the branch j fo that the whole plant in this ftate forms itfelf from a very complexly branched figure, into a fort of ftrait cy- lindric one. That motion which has, of all others, the greateft effect upon this plant, is a making one. Thefe three motions of the plant are performed by means of three diftinet and fenfible articulations ; the firft that of the fingle leaf to its pedicle, the fecund that of the pedicle to its branch, the third that of the branch to the trunk. The primary motion of all which, is the clofing of the two halves of the leaf upon their rib, which ought alfo to be performed in a fimilar manner, and by a fimilar articulati- on. This, however, is much lefs vifible than the others. Thefe motions are wholly independent on one another, as
I may be proved by experiment. It fhould appear, that if the ftalks are moved and collapfc toward the branches, or
' thefe toward the trunk, that the leaves, whofe motion is ufu- ally primary to thefe, fhould be affected alfo; yet experi-
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