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many other of thefe fmall animals, of feveral rings or joints ; it has eleven of thefe between its head and its tail ; they
are all roundifh, and very well refemble a firing of beads. The creature is almoft always in a bending figure repreSent- ing a fyphon ; its head and tail are always placed near one another, while the body is elevated and forms an arch above them. The head, the tail, and the ring joining to the tail, are the parts constantly kept in the water ; and the nine other rings, or at leafl feven of them, lie upon dry land. The constant habitation of the animal, is at the edges of Handing waters. It constantly draws back if more of the body is wetted, and plunges in deeper if lefs than the al- lotted portion is fo. The animal is not more than two thirds of an inch long : it is therefore much better distin- guished when kept in a vcSSel of water, than while it is in a pond. The uneafinefs of the creature at being too much or too little immcried, is eafily feen; for if the vefFel be Hoped fo as to drain the water from it, it very fpeedily fol- lows it down the fide of the veflel; and if it be floped the contrary way, fo as to make the water cover it too far, it as readily climbs up to get in part out of the reach of the wa- ter. Its manner of moving is very particular ; for neither the head nor the tail feem concerned in it, but the higheft part or Sixth ring of the body, which in its crooked ftate makes the fummit of the arch, is what moves firft, and draws all the other parts to follow it, the creature continuing in Its bended poSture while it moves. It does not move by vermicular progreflion, as fome animals do ; but has regular feet. Thefe indeed are (o fmall as not to be diftinguifhable without the afliftance of glades ; but when feen, they are found to be one of the great fingularities of the animal. Mem. Acad. Par. 1714.
The feet, contrary to their pofition in all other animals, are in this creature placed upon its back. Hence the creature naturally lies down upon its back as other creatures do up- on their bellies, and as it lies the mouth and the anus turn upwards. But this is not peculiar to this animal, for there are fome flies, and other water Infefis, which always fwim upon their backs, and have their mouths pointed upwards, that they may take their food, which is uSually placed above them ; and the fame reafon is to be given in regard to this InfeSi. Its feet are ten in number, placed on the Separate rings, two on a ring. There are only four between the Sixth ring and the head ; but thefe are larger than the other Six. They are very Short, and much reSemble the flender legs of Silk- worms, or other caterpillars ; and their extremi- ties are in the Same manner flatted, and armed with num- bers of little hooks. The four firft legs are bent towards the head, and the other fix are bent the contrary way, or towards the ta'il v There is great providence in this diSpofi- tion of them; for as the creature is ufually in an arched po- Sture and moves in that figure, the ten legs tho' they are placed contrary ways in regard to the head, are all placed in the fame direction in regard to the Sixth ring, which is as the head to other animals, the part which begins all mo- tion. By this difpofition of the legs the animal has a greater variety of motion, than any other creature ; for in an ex- tended poSture it can run with equal Swiftnefs backwards or forwards, by ufing the one or the other Set oS its legs ; and in its arched pofition it can, hefide the common motion forwards, move Sideways either to the right or left with •great facility, which is of great ufe to it when it wants to change its place, by moving only a little way. Eefide all thoSe motions, it has alSo the power of Swimming like other worms, which it exerts by turning and twifting its body about when it is by any accident plunged all over in the wa- ter. This, however, Seems an unnatural pofition to it, and it never Seems to get into it but by constraint, and then al- ways gets out of it again as Soon as it can, by Swimming to the fide. It is almoft continually feeding, tho' itsmorfels are but Small, being only fitch animalcules as microScopes dis- cover in waters.
The belly of this Infefi is of a deeper brown than its back, and the rings have on this fide certain Spots Surrounded with Short hairs, in the manner of the tracheae of feveral Infers, and probably they Serve the animal for the Same purpofe of reSpiration. The back is white and transparent, and its rings have none of thefe marks ; but they beautifully Shew by their tranfparence what paSTes in the body of the animal. There may be obServed near the anus a pipe, or circular canal, like the pifton of a fyringe, which is continually play- ing, and approaching to or receding from the anus. The Same Sort of motion is alfo perceived within the third ring of the body, in a pipe or canal, which feems only a conti- nuation of the former, and poflibly the heart of the creature is Situated there. Mem. Acad. Par. 1714.
Mufe-lxsECT. See the article Musk.
Hearts of Insects. See the article Heart,
INSIDIANT Bjfeafes, a term uSed by Some authors, to ex- preSs fuch difeafes as Shew no evident Symptom, but remain latent a long time in the body, and axe ready to break forth in an unexpected manner, and as it were by Surprize.
INSTEP, in the manege, is that part of the hinder. leg of a horfe, that correfponds to the Shank in the fore-leg, extend- ing from the ham to the pattern joint.
INSTITA, a word ufed by the chirurgical writers,, for a fillet or other bandage of that kind; and by medicinal writers,. for that fort of flat worms bred in the interlines, called by many the tape-worm, or flat-worm. Caft. Lex. Med. in voc. INSTITUTORES, in botany, that Set of authors in this Science who have laid down certain Settled rules, axioms, and institutions in it. Linnesi Fund. Bot. p. 2.
INSTRUMENT (Cycl)— P^^-Instruments, in Surgery. See the articlePoCKET.
INSUFFLATIO, a term uSed by Some writers in medicine, to- expreSs the blowing into any part, in order to convey the fumes of medicines into it.
INSULTUS, a word ufed by the writers in medicine to Sig- nify the accefs of the paroxyfm in intermittent diSeafes ; or Sometimes the firft invafion of a diSeaSe.
INTEGRANT Parts, in philoSophy, the Similar parts of a. body, or parts the fame and of the Same nature with the whole ; as filings of Iron are the integrant parts of iron, and have the fame nature and properties with the bar they were filed oiF from. The chemifts diftinguifh in their resolutions of bodies between the dividing or refolving them into inte- grant parts like theSe ; and what they call constituent parts, that is, diflimilar parts, or the principles of the bodies they work upon. Thus when crude mercury is diflblved in aqua- fortis, tho' held imperceptibly in the menftruum, yet when that menftruum is diluted with water and a copper plate is SuSpended in it, the menftruum leaves the mercury to work, upon the copper, and the mercury Subfides unaltered and in its own natural form ; the mercury therefore, in this opera- tion, was only divided into its integrant parts, or fmall par- cels of the Same nature and properties of the whole ; but when artificial cinnabar is reSoIv'd or divided into crude mercury and Sulphur, neither of thefe are of the Same na- ture and properties with the cinnabar, and are not its inte- grant but its constituent parts. This therefore is the divid- ing a body into its conftituent parts or principles. Shaw's Lectures, p. 15.
INTEGRUM Folium, among botanifts. Sec the article Leaf.
INTENSUM Diatonum. See the articles Diatonic, and Genus.
INTENTION, {Cycl) intcntio, Sb-iWkj in the antient mufic, was uSed to denote the paSSage of the voice from grave to acute. Arijtoxen. p. 10 — 13. Arijlid. Quint, p. B, 9. Gaudent. p. 2, 3.. Euclid, p. 2. Edit. Meimbom.
INTER Canem & Lupum, in law, words uled formerly in ap- peals, to Signify that a crime was committed in the twilight,. 1. e. inter diem C3" noilem, &c. This part of a day has di- vers other denominations : Thus, in Some parts of England they call it ?nock-Jl)adow, corruptly muck-jbade ; and in the north, day-light's gate ; others Say, betwixt hawk and buz- zard. Cowel, Blount.
INTERCAPSULARIA, in anatomy, a name given by Soma writers to the cavities between the Scapulae and the ver- tebrae.
INTERCEPTED Axis, in conic Sections, is the fame with what is otherwise called the Abjcijfa. See the article Ab- scissa, Cycl
INTERCESSION, Intercejfio, was ufed in antient Rome, Sor the act, of a tribune of the people, or other magistrate, by which he inhibited the acts of other magistrates ; or even in cafe of the tribunes, the decrees of the fenate. Veto was the Solemn word ufed by the tribunes when they inhi- bited any decree of the Senate, or law propoSed to the peo- ple 3 . The general law of thefe InterceJJions was, that any magistrate might inhibit the ads of his equal, or inferior ; but the tribunes had the Sole prerogative of controuling the acts of every other magistrate, yet could not be controuled themfelves by any b . — [ a Middlet. of Rom. fen. p. 160. * Mddlet. ibid.]
INTERCIDENT Pulfe, a term ufed by medical writers, to exprefs a Sort oSpulfe, in which between two regular Strokes there is perceived a third irregular.
INTERCOSTAL (Q-f/.)— Intercostal Mufcles. Thefe muScles are So many thin flefhy plates, two between every two ribs, an external and an internal, cloSely joined to- gether with only a thin cellular web between them. The fibres of the external Intercojials are very oblique near the vertebrae ; but this obliquity decreafes infenfibly as they ap- proach the anterior extremities of the ribs. Their inSertiqns begin at the ligaments, by which the ribs are faftened to the tranSverSe apophySes. They are a little tendinous, and run a Small Space beyond the edge, on the outride of each rib. The fibres of the internal Intercojials are in general fhorter and lefs oblique than the former ; they fill almoft: en- tirely the interitices between the cartilaginous portions, and they are covered on the outfide by a ligamentary membrane,
1 the fibres of which running in an oppofite direction to thoSe of the mufcles, have been miftaken for continuations of the external Intercojials, over which this membrane is alfo Spread, only a little diminished in thicknefs.
Any portion of the breaft of an animal may be boiled fo much that the flefti eafily parting Srom the bones, the ribs
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