Page:Cyclopaedia, Chambers - Volume 2.djvu/927

 T Y M

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T Y M

ther j which the modern Heralds more ufually call the fecond or third Houfe.

TYMBER of Skins, is the Number of forty Skins. See Timber.

TYMPAN, or Tympanum, in Architecture, the Ground or Area of a Pediment ; being that which is in a Level with the Naked of the Freeze. Or it is the Space included be- tween the three Cornices of a triangular Pediment, or the two Cornices of a circular one. See Pediment,

Sometimes the Tympan is cut out, and the Part fill'd with an Iron Lattice to give Light ; and fometimes it is enrich'd with Sculpture, in Bas Relief, as in the Weft Front of St. $?aul\ in the Temple of Caftor and Pollux at Naples, &c.

The WordTYMPAN is alfo ufed for that Part of a Pedeftal calFd the Trunk or Dye. See Pedestal. See alfo Dye.

Tympan, among Joyners, is alfo attributed to the Pannels of Doors. SeePiNNEL.

Tympan, among Printers, is a Frame belonging to the Prefs, cover'd with Parchment, on which every Sheet is placed, in order to be printed off! See Printing 'Prefs.

Tympan of an Arch, in Architecture, is a triangular Space or Table in the Corners or Sides of the Arch ; ufually hollow'd and enrich'd, fometimes with Branches of Laurel, Olive-tvee, or Oak ; or with Trophies, &c. fometimes with flying Figures, as Fame, &C or fitting Figures, as the Car- dinal Virtues. See Arch.

TYMPANITES, or Tympany, in Medicine, a flatuous Tumor, or Swelling of the Abdomen, or Belly ; very hard, equable, and permanent ; whereby the Skin is ftretch'd fo tight, that when ftruck, it gives a Sound like that of a Drum. See Tumor.

The Tympanites is a Species of a Dropfy ; but what the Caufe and Seat of the Difeafe is, or what the morbific Mat- ter is that occafions the Tumor, Phyficians are not at all agreed. See Dropsy.

Wind certainly makes a principal Part of the morbid Mat- ter 5 but this is fcarce ever found without Water, excepting at the Beginning 5 fo that fome will not allow of any Diffe- rence between the Tympany and the Afcites.

Some fuppofe it to arife from a watery Humour extrava- fated and rarify'd into Vapour ; and by a Property common to it with common Air, corrupting the Parts..

But this 2?oerhaave makes a particular Kind of Tympa- nites or Wind Dropfy ; and adds, that it is cured like the Afcites or Water Dropfy, by Tapping, &c. SeeTAPriNG and Ascites.

Others will have xhcTympanites to arife from the Air's infinuating itfelf thro J Perforations in theputrify'd Interlines.

A 'Tympanites from this Caufe, Boerhaave, who makes it

a peculiar Clafs, obferves, is almoft always incurable.

Willis fets afide this latter Caufe, and accounts for the Difeafe from an Irregularity in the Animal Spirits belonging to the Vifcera, which rufhing tumulruarily into the nervous Fibres, bloat them up ; Thus is the Peritoneum inflated, the Inteftines diftended, and the Mefentery, and other Vifcera, render'd turgid ; and while this is doing, that the Vacuities left in the tumify'd Vifcera may be fill'd up, a Quantity of the Humour contain d in them is rarify'd into Vapour, which prefently fpreads in Blafts through the vacant Places.

Others account for the tympanites from a Convulfion of the^Mufcles of the Abdomen, &c.

W. Littre has propos'd a new Syftem of the Tympamtes, built on a great Number of Obfervations. — According to him, it does not proceed from any Convulfion of the Abdo- minal Mufcles, nor from any Air contain'd in the Cavity thereof, or in the Thorax, the Mefentery, or Epiploon ; but from the Air inclos'd in the Stomach and Inteftines, which fwells them exceffively.

This Air, always carry'd into thofe Parts with the Food, maintains a kind of Equilibrium therein; oppofing, on the one Hand, the too great PrefTure on that long Canal when empty of Food ; and finding, on the other Side, in the Spring of the Coats of the Stomach and Interlines, an Ob- itacle'capable of preventing its too great Dilatation.

If this Equilibrium chance to be deftroy'd by the Irrita- tion of the Fibres, whole Spring in that Cafe prevails over that of the Air ; this latter is expell'd either upwards or downwards, or both : (whence Belching, &c.) But if the Equilibrium come to be broke by the Force of the Air, ren- der'd fuperior to that of the Fibres, by thofe latter being left deftitute of Spirits, from the Blood's being impoverifh'd after a long Sicknefs ; in that Cafe, the Air, rarifying itfelf beyond Meafure, fwells the Cavities it is contain'd in.

If it be demanded, Why when the Stomach and Inteftines are fo full of Wind, none of the Wind efcapes, either thro' the Anus, or by the Mouth, which ules to be expell'd by thofe Paflages ?

M. Mery folves the Paradox thus : According to this The- ory, the Fibres, both of the Stomach and Inteftines have loft their Spring, at Ieaft in Part, and are in an imperfect. Palfy 5 but the Winds evacuated either by the Anus or Mouth, are Winds which thofe Vifcera expel out of their Cavities, by

putting them in a State of Contraction capable of furmounting the Forces which oppofe the Egrefs of the Matters con- tain'd in thofe Cavities. — Thefe Forces are two Sphincters, one whereof fhuts the upper Orifice of the Stomach, and the other the Anus : But paralytic Vifcera, i. e. Vifcera deftitute of Spirits, in which alone confifts the Strength of the Muf- cles, cannot overcome the Refiftance of thofe two Mufcles : Whence the Wind, therefore, cannot efcape thro' its ufual Out-lets.

The "Tympanites rarely kills of itfelf; but frequently de- generates into an Afcites. — Catharticks rather aggravate than alleviate it : Antihyftericks, Antifcorbuticks, 1 Chaly- beats, and Strengthners are of ufe, before it befallen into an Afcites. Equal Quantities of Leek and Elder Leaves mix'd analytically, is a fam'd Empirical Medicine, which has often prov'd effectual when every thing elfe had fail'd.

J Tis ufual to apply Carminatives to the Belly, as the Em- plaftcr of Cumin-Seeds, &C, and alio to ufe Carminatives mix'd with Cathartics, Diuretics, f£c. internally : But if the Difeafe proceed from a Paralytic Caufe, deftroying the Tone of the Fibres of the firft Paflages, what is of Ufe in rectifying of Paralytic Diforders, where the Tenfion of the Fibres are infufF.cient, wiil doubtlefs for the fame Reafon be of Ufe here. Sec Palsy.

TYMPANUM, Tvp-mvov-, 2)rum ; a mufical Inftrumenr, which among the Ancients, confifted of a thin Piece of Lea- ther or Skin, ftrerch'd upon a Circle of Wood or Iron, and beat with the Hand. See Drum.

Tympanum, Tympan, in Mechanicks, is a kind of Wheel plac'd on an Axis or Cylindrical Beam, on the Top of which are two Levers or fix'd Staves, for the more eafy turning the Axis about, in order to raife a Weight requir'd. See Wheel.

The Tympanum is much the fame with the Peritrochium ; but that the Cylinder of the Axis of the Peritrochium is much fliorter and lefler than the Cylinder of the Tympanum. See Peritrochium.

Tympanum of a Machine, is alfo us'd for any hollow Wheel, wherein one or more People, or other .Animals, walk to turn it ; fuch as that of fome Cranes, Calandcrs, l$c. See Wheel.

Tympanum, in Anatomy, or Membrana Tympani, is a thin tender Skin or Membrane, ftretch'd upon a Bony Circle, in the Meatus Auditorius of the Ear, which it /huts ; and fuppos'd to be the immediate Organ of Hearing. See Ear.

The Tympanum, popularly call'd the 'Drum, with refpedl: to the creel Pofture of the Body, is fituatc obliquely, facing downwards ; whence it is that we hear Sounds coming from below, better than thofe from above. See Drum.

Its external Surface is a little hollow'd in the Middle. — It is compos'd of two Membranes ; or, as others will have it, of only two or more Lamella:. — It has a Perforation, or, at leaft, a difengaged Part, which admits of the PafTage ot Wind, and, in fome, of Smoak from the Meatus a Palato.

Behind it is a Cavity of the Os Petrofum, call'd Tympani Cavitas, and by fome fimply Tympanum ; wherein are four little Bones, viz. the Malleolus, Incus, Stapes, andOsOrfo- culare : Which fee under their refpeSivc Articles, Malleo- lus, £f?£.

Within the Cavitas Tympani, Vieujjens has difcover'd a very fine thin Membrane, ferving to fhut the Door of the Labyrinth, and prevent the internal Air from having any Communication with the external. ■*?- The Membrana Tym- pani has a remarkable Branch of a Nerve pairing on its inter- nal Surface between the Incus and Malleolus, call'd the Chor- da Tympani. See Chorda.

The Tympanum, Dr. Willis takes to be a kind of prepara- tory Inftrument to Hearing ; and its Office to be to receive the firft Impreffions of the Sound, or the fenfible Species, and to convey them duly modify'd and proportion 'd to the Senfo- rium. See Sound.

Its Office, in erfeef, with refpect. to the Senfe of Hearing, feems to be the fame as that of the Pupil of the Eye with regard to Seeing : Each of them prevent the Ingrefs of too many Rays, temper and foften them, and deliver them, as it were, commenfurate to the Senfory ; upon which, if they fliould fall immediately, they might be apt to fpoil its deli- cate Conftitution. See Pupil.

The Tympanum, it's true, does not hear 5 but it contributes to the better and fafer Hearing. — That it may do the Office of a Porter the better, 'tis neceSary its Expanfe fliould, like the Pupil, be contracted and relax'd on Occa&m; and to^this purpofe ferve the four little Bones above mention'd, which have the fame Ufe in ftraining and relaxing, as the Braces of the War Drum have in that Inftrument. — By means of this ExtcnfionandRetraaion, theTympanum is made to corre-' fpond to all Sounds loud or languid ; as the Pupil does to all the Degrees of Light. See Hearing.

But what makes the Ufe of the Tympanum appear the lefs confiderable, is, that there are Inftances where the Hearing has been perfea without any Ufe of a Tympanum. — Mr. Chefelden relates, that he broke the Tympanum in both Ears

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