Page:Cyclopaedia, Chambers - Volume 2.djvu/842

 TEE

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TEE

Technical Words, are what we otherwife call terms of Art. See Term.

TE DEUM, a kind of Hymn, or Song of Thankfgiving, ufed in the Church, beginning with the Words te X)eum laudamtis, Wefraife thee, God.

Tis ufed to be fung in the Rotnifi Church with extraor- dinary Pomp and Solemnity, upon the gaining a Battle, or other happy Event. The te tteum is ufually alcrib'd to St. Amhrofe, and St. Atigttflin.

TEETH, Hemes, in Anatomy, little hard fmooth Bones, let in the Gums, and ferving to mailicate or chew the Food, to bite, £i?c. See Food, Mastication, £jfc.

Men, and mod terreilrial Animals, as alfo fome Fifb.es, have two Rows of Teeth, the one in the upper Jaw, and the other in the lower. See Gum and Jaw.

Jn Men, the ordinary Number of Teeth is 32, fixtecn in each Jaw ; all fix'd in peculiar Sockets, call'd Alveoli ; by the Juncture or Articulation, call'd GomJ>hofs, and by the Joyners, Pegging. See Gomphosis.

They are of three Sorts : Thole in the fore Part of each Jaw are call'd Incifores, Cutters ; and are four in Number in each Jaw, broad, thin, and flat : Some call them the Pri- mores, becaufe they appear the firft ; others the Adverft ; and others the Ridentes, Laughers, becaufe they Ihew themfelves firft in Laughing. See Incisores.

Behind thefe, on each Side of each Jaw, ftand two which are a little more prominent, and pointed, call'd Canint, by the People Eye-teeth, becaufe Part of the Nerve which moves the Eyes is inferred into them ; whence the Danger of pulling them out. SeeCANiNi.

Behind thefe are five in each Jaw, call'd the Molares or Grinders, being thofe which in Men ferve chiefly for Mafti- cation. See Molares.

The Incifores have generally only a (ingle Root, or Twang; the Canini fbmetimes two ; and the Molares three or four, efpeciaily the hind ones, which are put to the greateft Strefs.

The teeth, according to Peyer, are form'd of convolv'd Skins, harden'd and bound together by a vifcid Mucus : And if we view the Grinders of Deer, Horfes, and Sheep, Igc. we mall find great Reafon to be of his Mind.

Others fpeak of their Formation otherwife. The Sockets, Dr. gltiticy obferves, are lin'd with a thin Membrane, upon which are feveral Yeffels, thro' which there paries a thick tranfparent Humour, that, as it increafes, har- dens in form of Teeth ; and about the feventh or eighth Month after Birth, they begin to pierce the Edge of the Jaw, tear the Periofteum and Gums, which being very fenfi- ble, create a violent Pain, and other Symptoms incident to Children in the Time of Dentition. See Dentition.

The teeth begin nor to appear all at a Time 5 but firft. the Tlentes inciftvi of the upper, and then thofe of the lower Jaw appear, becaufe the thinneft and lharpefl ; after them come out the Canini, becaufe they are fliarpcr than the Molares, but thicker than the Inciftvi ; and laft of all the Molares, becaufe they are thickelt and blunteft. ,.,..,,.

Of this vifcous tranfparent Liquor, which is indurated into the Subftance of the teeth, there are two Lays, one below the other, divided by the fame Membrane which covers all the Cavity of the Jaw : The uppermoft Lay forms the teeth which come out firft ; but about the feventh Year of Age they are rhruft out bv the teeth made of the undermoft Lay, which then begin to fprout ; and if thefe teeth be loft, they never grow again. .-,.«>»

If fome have been obfcrv'd to fhed the.r teeth twice, they have had three Lays of this vifcous Humour, which hardly ever happens. "

About the one and twentieth Year, the two laft ot the they arife when the Perfon is at Years of Difcretion.
 * >/«/«ra fpring up, and are call'd "Denies Safienttf, becaufe

The teeth, M. de la Hire the younger, has found to have all that Part which Hands out beyond the Jaw, cover'd with a peculiar Subftance quite different from die Bone, which he calls Email, or Polidi.

This Email, by fome others call'd the tenofeum, is com- pos'd of an Infinity of little Fibres, which grow to the Bone by their Roots, much like Nails or Horns. See Nail.

This Compofition is very difcernable in a broken Tooth, where the Origin and Siruation of the Fibres are apparent. M dela Hire is perfwaded, that the Growth of thefe Fibres is perform'd much like that of Nails If by any Accident a little Part of this Email be broke off fo that the Bone is left bare, that is, if the very Roors of rhe Fibres be raken away, the Bone, in that Part, will grow carious, and rhe tooth inevitably perifh; there being no Bone in the Body that can bear the Air. See Bone.

Indeed, in fome Perfons the Email is very much wore and Jhatter'd, by rubbing them much with Dentnfices, pc. fo that the Bone appears thro', and yet the tooth keeps found ; but the Reafon is, that the Bone is not quite bare, but there is ftill a thin Lay of the Email which preierves it ;

but this Lay being thin enough to be tranfparent, the yellow Bone is feen thro' ir.

Sometimes alfo a tooth breaks, and the Bone is left bare, yet the Perfon does nor find any Pain or aking from it : The Reafon is, that the Hole in the Root or Twang of the tooth thro' which a little Branch of a Nerve enters that renders the tooth fenfible, being quite ftopp'd up by Age, or the like, has pinch'd off the Nerve, and taken away all Communication between the tooth and the Origin of the Nerves, and, by Confequence, all Senfibility.

It alfo happens in fome teeth, that the Fibres are only in little Sheaves or Bundles, whole upper Extremities meet, but not their lower ; as is the Cafe in moft of the Grinders, where the Separation of the Bundles is apparent. Hete, if the upper Extreme of the Fibres chance to be broken, or wore off, the Separation between two of the Bundles often enlarges itfelf, fb as to admit fome hard Particle of the Food, by which Means a little Aperture being made thro' the Email, the Bone is laid bare, and the tooth fbon rots. This Incon- ■ venience is remedy'd a little by flopping up the Hole with Lead, which prevents the fharp pungent Parts of the Food from penetrating to the Bone, and there occafioning Pain. See Odontalgy.

What we have laid is illuftrated by the adjoining Figures, where A C F H expreffes the Extremity of the Jaw the teeth are fer in ; AFC and F G H the Roots or Twangs of the teeth inclos'd in the Jaw; ADCB and FLHIL the Entail, compos'd of little Fibres ranged afide of each other, which cover all that Part of the tooth without Side the Jaw ; I I feveral Threads join'd at the upper Extremity, but apart at the lower; M M Holes thro' which the Nerves enter the Roots of the teeth ; N N a tooth doled up.

The teeth, Mr. 'Derham obferves, furnifli us with a notable Inftance of the Wifdom and Goodnels of the Creator : Their peculiar Hardnefs is very remarkable, con- fidering the tender Subftance they are form'd of. See Bone.

The Ancients, and even Riolantis, among the Moderns, have held them to be^incombuftible, and the only Part of the Body that was fo s on which Account they were placed with great Care in the Urns among the Afhes of the De- ceas'd : But the Opinion is falfe, there having only been two found in the Tombs of Wefifhalia, one of which was half calcin'd.

Another popular Error is, that the teeth continue grow- ing for ever, even in old People, to the Hour of their Death. M. dela Hire obferves, 'tis only the Email or Polifli chat grows, which is a Subftance very different from the teeth.

The Form, Difpofition, and Order of the teeth are ad- mirable : The foremofl: weak and far from rhe Centre, as being only Preparers to the reft ; the others being to grind and mince, are accordingly ftronger, and placed near the Centre of Motion.

Galen puts the Cafe, that the Otder of the teeth mould have been inverted, and the Grinders, e.gr. put in the Place of the Incilors ; and asks, what Ufe the teeth had then been of, and what Confulion would not there have aroie by fuch a flight Overfight in the Qifpolal only ? Upon which he argues, that if any Perfon fhoulcf difpol'e a Company of 52 Men, the Number of the teeth, in a juft Order, we mould judge him an intelligent Perfon: Why then mould we not judge the fame of 'the Creator, S?c. ? <De lifts tar-

tium. ' ., ■ 1 r

Again, their various Forms in various Animals is no lels confi'derable, being all curioufly adapred ro rhe peculiar Food and Occafions of the feveral Species of Animals : Thus in rhe Rapacious they are fitted for rhe catching, holding, and tearing the Prey; in Herbaceous for rhe Gathering and Communition of Vegetables ; and in fuch as have no teeth, as Birds, the Bill fupplies the Defefl. See Bill.

Add, that the temporary Defeft of them is no els ob- fervable in fome : That Children, for Inftance, Ihould have none while rhey are not able ro u(e them, but to hurt them- felves, or the Mother ; and that at the very Age when they can take in the more fubftantial Food, and live without the Breaft, and begin to need teeth for the Sake of Speech ; that then, we fay, their teeth (hould begin to [ A a a ] appear,