REV
R I F
A twig of willow, poplar, or many other trees being planted in the earth* takes root, and becomes a tree, every piece of which will in the fame manner produce other trees. The cafe is the fame with thefe worms j they are cut to pieces, and thefe feveral pieces become perfect animals ; and each of thefe may be again cut into a number of pieces, each of which will in the fame manner produce an animal. It had been fuppofed by fome, that thefe worms were oviparous ; but Mr. Bonett, on cutting one of them to pieces, having obferved a flender fubftance refembling a fmall filament to move at the end of one of the pieces, feparated it, and on . examining it with glaffes, found it to be a perfect worm of the fame form with its parent, which lived and grew larger in a veuel of water into which he put it. Thefe fmall worms are eafily divided, and very readily complete themfelves again, a day ufually ferving for the production of a head to the part that wants one, and in general the fmaller and flenderer the worms are, the fooner they complete themfelves after this operation. When the bodies of the large worms are exa- mined by the microfcope, it is very eafy to fee the appear- ance of the young worms alive and moving about within them ; but it requires great precifion and exadtnefs to be cer- tain of this ; fince the ramifications of the great artery have very much the appearance of young worms, and they are kept in a fort of continual motion by the fyftoles and diaf- toles of the feveral portions of the artery which ferve as fo many hearts. It is very certain, that what we force in re- gard to thefe animals by our operations, is done alfo natu- rally every day in the brooks and ditches where they live. A curious obferver will find in thefe places many of them without heads or tails, and fome without either ; as alfo o- ther fragments of various kinds, all which are then in the aft of completing themfelves ; but whether accidents have reduced them to this ftate, or they thus purpofely throw off parts of their own body for the Reproduction of more ani- mals, is not eafy to determine. They are plainly liable to many accidents, by which they lofc the feveral parts of their body, and mult perifh very early, if they had not a power of reproducing what was loft ; they often are broken into two pieces, by the refiftance of fome hard piece of mud, which they enter ; and they are fubjeft to a difeafe, a kind of gan- grene rotting off the feveral parts of their bodies, and muff inevitably perifh by it, had they not this furprizing pro- perty.
This worm was a fecond inftance after the polype, of the furprizing power in an animal of recovering its moft ef- fential parts, when loft ; but nature does not fecm to have limited her beneficence in this refpeft to thefe two creatures ; Mr. Bonett tried the fame experiments on another fpecies of ■Water-worm, differing from the former in being much thick- er : This kind of worm, when divided in the fummer feafon, very often fliews the fame property ; for if it be cut into three or four pieces, the pieces will lie like dead for a long time, but afterwards will move about again, and will be found in this ftate of reft to have recovered a head, or a tail, or both. After recovering their parts, they move very little, and according to this gentleman's experiments, feldom live more than a month.
It mould feem that the more difficult fuccefs of this laft kind of worm, after cutting, and the long time it takes to reco- ver the loft parts, if it do recover them at all, is owing to its thicknefs ; fince we always find in that fpecies of worms ■which fucceeds beft of all, that thofe which are thinneft al- ways recover their parts much fooner than the others. The water infects alfo are not the only creatures which have 'this power of recovering their loft parts, The earth affords us fome already difcovered to grow in this manner from their cuttings, and thefe not lefs deferving our admiration than thofe of the water; the common earth worms are of this kind. Some of thefe worms have been divided into two, o- thers into three or four pieces, and fome of thefe pieces, after having palled two or three months without any appearance of life or motion, have then begun to reproduce a head or a tail, or both. The Reproduction of the anus, afcer fuch a ftate of reft is no long work ; a few days does it, but it is other- wife with the head, that does not feem to perform its func- tions in the divided pieces, till about feven months after the feparation. It is to be obferved, that in all thefe operations both on earth and water-worms, that the hinder part fuffers
- greatly more than the fore part in the cutting, for it always twifts itfelf about a long time, as if actuated by ftrong con- 'vulfions; whereas the head ufually crawls away without the appearance of any great uncafinefs.
REVERSION of Series (Cycl.) — The problems mentioned , under this head in the Cyclopaedia may indeed be folved by the method of Rcverfion of Series, but are only particular cafes of it, and not a general account of that method, which is to be underftood thus : The value of any indefinite quan- tity* h f° r inftance, being expreffed by an infinite Series of fimple terms, including different powers of another variable quantity, x t the value of x is thence to be found, by a kind of rcverfed operation, expreffed in a Series of fimple terms, including different powers of the quantity y. Thus, if y = x — s * a + t * * — £ #* + &c. by the Reverfion of
the Series, we fhall have} *■ ==J» + £.? *4" iy ^ 4* wJ 1 4 "^ t4s y 5. Thus alfo, if dx-\- b x * -f- c x 3 -f. dx 4- -j- &c. ^gyJ^byz-^iyZ +^>"*+ &c. x may be found by this method, expreffed by the powers of y. There are various ways of doing this. One, which is often convenient, is, by afiiiming a Series with indeterminate co- efficients of a certain form; examples of which are given under the head Form of a Series, Append. See Mac Lau- rin's Algebra, pag. 263. and Mr. De Moivre, in the Phil. Tranf. N° 240.
Other methods may be feen in Mr. Stuart's explanation of Sir Ifaac Newton's Treatife of Analyfis by equations of an infi- nite number of terms, p. 455.
RESERVATORY, a term fometimes ufed in a fynonymous fenfe with Refervoir, See the article Reservoir, Cycl.
RETURN, in the military language, denotes the lift of the fick, given in once a week by the furgeon to the command- ing officer of a regiment.
Commiifioned officers are not put in the Returns, which, on that account, are but an imperfect lift of the fick. Twelve fick, in a battalion of 780 private men, is the loweft Return that can be expected, even in the moft healthy fea- fon and climate, as well as beft quarters. Returns are often much higher, but feldom exceed feven ty in a battalion. It is to be obferved, that Returns include all accidents un- fitting a foldier for duty. See Pringle, Obferv. on the Dif. of the Army, p. 12, 36.
RHAPONTICOIDES, in botany, a diftinft genus of plants, according to Vaillant, but efteemed only a fpecies of Cen- tauria by Linnaeus. See the article Centauria.
RHAPONTICUM, a diftinft genus of plants, according to Vaillant, but comprehended under the Centauria by Linnaeus. See the article Centauria, Append.
RHETORICAL Accent, among Hebrew grammarians. See the article Accent, Cycl.
RHEUM, in botany, the name given by Linnaeus to Rhubarb. See the article Rhubarb, infra.
RHEUMATISM (Cycl.) — This is a difeafe incident to win- ter, and owing, chiefly, to a fuppreflion of perfpiration. In a complete and obftinate Rheumatifm, the joints are often conftderably fwelled and inflamed ; but in fevers with rheu- matic pains, this is feldom the cafe. Accordingly, in thefe laft, the cure may be effected in a few days, by twice or thrice bleeding, and promoting a diaphorefis by the cooler medi- cines, particularly vinegar-whey. But if the Rhewnatifm be attended with violent pains or fwelling of the joints, fweating is reckoned improper ; fo that the cure muft be obtained by repeated and almoft daily bleedings, till the fever is gone, and the pains either entirely removed, or rendered much eafier.
If the pain and fwelling of the joints remain after the fever is abated, three or four leeches may be applied to the part where the inflammation and tumour are greateft ; letting the blood ooze, till it ftops of itfelf. As the relief hereby obtained is fometimes confiderable, and the evacuation but fmall, the re- petitions need not be limited. But, then, no benefit is to be expected from leeches in any pains of the joints, not attended v/ith both inflammation and fwelling.
In the true acute Rheumatifn, internal medicines avail little. The beft perhaps are the neutral falts, with very fmall doles of camphor, fo as neither to heat or force a fweat. As to diet, it ought to be of the loweft kind. Outward applications are alfo to be omitted, as long as any fever or inflammation re- mains. The fpirituous and volatile liniments inflame, and the emolient fomentations, though they give eafe for the time, do harm by relaxing, unlefs very fparingly ufed. If there is no inflammation, the aking parts may be rubbed with flannel, and anointed with the linimentum volatile or fapo- naceum, according as the ikin is too much hardened or re- laxed by the ufe of the one or other. After the patient has continued fome time in this courfe, his recovery will be quickened by the ufe of the cold-bath, or the bark ; and to thofe who can afford it, riding is fpecific. Rringle, Obferv. on the Dif. of the Army, p. 152, feq.
RHUBARB, in botany, the Englifh name of a diftinft genus of plants, of which there is only one known fpecies. See the article Rhabaebarum, Suppl.
Jldoni' s-Khvb a KB y the name of a fpecies of Lapathum, or dock. See the article Lapathum, Suppl.
RIB-zvort, a name fometimes given to the Rlantago of botanifts, See the article Plantago, Suppl.
RIBBAND-Screw-Jbell, the English name of the Turbo, with broad fpiral fafcise, and a fmall mouth. See the article Tur- bo, Suppl.
RIBES, in botany, a general name given by Linnaeus to the gooiherry and currant bufhes, which he makes one genus of plants, called by others Groffularia. See the article Grqs- sularia, Suppl.
RICE, the Englifh name of a genus of plants, known among botanifts by that of Oryza. See the article Oryza, Append.
RIFTS, a difeafe in horfes arifing from corruption lodged in the palate of the mouth. Ruft. Diet, in voc.
I RING-
