Page:Cyclopaedia, Chambers - Volume 2.djvu/393

 PER.

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P E R

The Word is compounded of the Greek crsp? about, and IftewZi Eye.

PERIOSTEUM, in Anatomy, a Membrane, pretty tough, and extremely fenfibie, covering the whole exterior Surface of all the Bones of the Body 5 the Teeth alone excepted. See Bone.

It is derived from the Dura Mater, and confifts principally of Fibres detach'd thence; befides which it receives other Fibres from the Membrana Communis of the Muiclcs, or as Dr. Havers imagines, from the flefhy Fibres of the Belly of the Mufcles, which interfect the Former.

That Part of it which covers the Cranium or Skull, is by a peculiar Name call'd the Pericranium. See Pericranium.

The Perio(leum is very thin every where ; tho' not every where alike. It adheres clofcly to the Bone ; and in fome Places is obferv'd to fend Fibres into the very Subftance thereof.

Its principal Ufe is to defend the Mufcles and Tendons from being fretted in their Aclion by the attrition of the hard Subftance of the Bones ; and to give Notice, by its fenfibility, of any Thing that might annoy the Bones.

Indeed, this lad Ufe is controverted j fome of the lateft Anatomifts maintaining that the Periofieum is infenfible.

The Word is form'd from the Greek ^tft about and b*iov. PERIPATETICKS, a Secf of Philofophers, the Followers of Arifiotle- 7 or the Maintained of the Peripatetic Philofo- phy; call'd alfo Arifiotdians. See Aristotelian.

Cicero tells us that Plato left two excellent Difciples, Xeno- crates and Arifiotle, who founded two Se£ts, which only dif- fer'd in Name; The Former taking the Appellation of Acade- micks, who were thofe that continued to hold their Confer- ences in the Academy, as Plato had done before ; the other who follow'd Arifiotle were call'd peripateticks ; from wEp/wttTSfe', I walk, becaufe they diiputed walking in the Lyceum. SccLyceum.

Ammonius fetches the Name peripatetic from Plato him- felf, who only taught walking ; and adds that the Difciples of Arifiotle, and thofe of Xemcrates were equally call'd peri- pateticks, the one Peripateticks of the Academy, the other Peripateticks of the Lyceum ; but that at length, the Former quitted the Title Peripatetic for that of Academic, On occa- sion of the Place where they affembled ; and the Latter re- tain'd limply that of Peripatetic. See Academic.

The greateftand be ft Part of Arifiotles Philofophy, he bor- row'd from his Matter Plato : Serramts affirms confidently, and fays he is able to demonflrate it, that there is nothing ex- quifite in any part of Anfiotlci Philofophy, Dialectics, Ethics, Politics, Phyfics, or Metaph)fics, but is found in Plato. And of this Opinion are many of the ancient Authors, Clemens Alexandrinus, ike. See Platonism.

Gale endeavours to Ibew that Arifiotle borrow'd a good deal of his Philofophy both Phyfical about the firfi Matter; and Metaphyfical about the firfi Being, his Affections, Truth, Unity, Goodnefs, £»?f. from the lacred Books; and adds from Clearchus, one of his (Arifiotle's) Scholars, that he made ufe of a certain Sfew, who aflilted him therein.

Arifiotle's Philofophy preferv'd itfelf in/z/w iwturalibus, a long Time ; none of his Followers or Commentators having daredto make any Innovations therein : Till the Beginning of the XIHth Century ; when it began to be new model'd. A reform'd Syftem of Peripatcticifm wasfirft introdue'dinto the Schools, in the Univeifity of Paris ; from whence it foon fpread throughout Europe ; aud has fubfilted in the Schools to this Day, under the Name of School Philofophy. See

SC HOOL, &C

The Foundation hereof is Arifiotle's Doctrine, frequently mifundeiftood; oftener mifapplied .* Whence the Retainers, thereto may be denominated reformed 'Peripateticks.

Out ofthefe have fprung at feveral times feveral Branches, the chief are the Thomifis, Scotifis, and Nominalifis, See each tinder its proper Article, Tiiomist,Scotist, and Nominal.

Peripatetic Philofophy, the Syftem of Philofophy, taught and eftablifh'd by Arifiotle, and maintain'd by his followers the peripateticks. See P*rip ateticks and Phi-

tOSOPHY.

A Specimen of the Peripatetic Philofophy, See under Aristotelian.

PERIPETIA, in the Drama, that part of a Tragedy wherein the Action is turn'd, the Plot unravel'd, and the whole concludes. See Tragedy.

The (Peripetia is properly the Change of Condition whether happy or unhappy, which the principal Perfon or Perfons un- dergo ; arifing from fome Difcovery or Incident, which gives a new turn to the Action.

The Peripetia therefore coincides with the Cataftrophe, or Unravelling; unlefs we make the peripetia to depend on the Cataftrophe, &c. as an effect on its Caufe. See Catastro- phe and Unravelling.

The Peripetia is fometimes induced by Remembrance or Difcovery,as inthe Oedipus,wheve the Meffenger fent from Co- rinth to invite Oedipus to the Crown, informs him that 'Poly- bus and Metope were not his Father and Mother; which be- gins a Difcovery, that Lmis, whom he had kill'd fc and Jo-

cafia whom he had then to Wife, were his Father and Mother^ and throws him into the deepelt Diftrefs. See Discovery. This Initance Arifiotle calls a double Peripetia.

The Qualities of the Peripetia are, that it be probable and neceflary; in order to which it mult be the natural Refult, at leaft the Effect, of the foregoing Actions, or of the Subject it- felf ; not ffart out from any foreign, or collateral Caufe.

Sometimes the Peripetia is occafion'd without any Difco- very ; as in the Antigone of Sophocles, where the Change in Croon's Fortune is produced by the Effect of his own Obftina- cy ; and fometimes by a mere Change of the Will, which, tho' the leait artful, yet, Mr. Z)ryden obferves, may be fo ma- nag'd as to become exceedingly beautiful.

Thefe two Cafes Arifiotle calls fimple Peripetias ; in thefe, the Change only confifts in a PafTage out of Trouble and Ac- tion, into Tranquillity and Reft. See Fable, Action, £#?.

The Word Peripetia is form'd from the Greek •js^nn- 7»c, fomething falling into a different State.

PERIPHERY, in Geometry, the Circumference, or Bounding-Line of a Circle, Ellipfis, Parabola, and other fimi- lar Figures. See Circumference, Circle, &c.

The Periphery of every Circle is fuppofed to be divided into 360 Degrees, which are again fubdivided, each into 60 Minutes, the Minutes into Seconds, &c. See Decree, Minute, SSta

The Divifions of Degrees, therefore, are Fractions, whofe Denominators proceed in a fexacuple Ratio; As, the Minute s i, Second -=p?4oi Third tf! — o- See Sexagesimal.

But thefe Denominators being troublefome ; in their ftead are ufed the Indices of their Logarithms ; hence the Degree, being the Integer, or Unit, is mark 'd by o, the Minute by, Second by " £$ft See Minute, Second, &c.

Geometricians demonstrate that a Circle is equal to a Tri- angle, whofe Bafe is equal to the Periphery, and Altitude to the Radius. See Triangle.

Hence it follows that Circles are in a Ratio compounded of their Peripheries and Radii. But they are alfo in a duplicate Ratio of the Radii ; therefore the Peripheries of Circles are to each other as their Radii : and fince the pheriphery of one Circle is to its Radius, as the Periphery of any other to its Radius ; The Ratio of the Periphery to the Diameter is the fame in all Circles.

The Word is form'd from the Greek -jift^a Qrcumfero^ I furround.

PERIPHRASIS, in Rhetoric, Circumlocution, a Circuit or Tour of Words, much affected by Orators, to avoid common and trite manners of Expreffion. See Circumlocution, Figure.

The Periphrafis is of good ufe on many occafions; and we are frequently forced to have recourfe to it, to make Things beconceiv'd, which it is not proper to name.

Tis a Piece of Politenefs tofupprefs the Names, and only intimate, or defign 'em. Thefe Turns of Expreffion are parti- cularly ferviceable in Oratory ; for the Sublime admitting of no direct Citations, there muft be a Compafs taken to insinu- ate the Authors, whofe Authority is borrowed. A Periphra- fis by turning round a proper Name to make it understood, amplifies and raifes the Difcourfe ; but Care muft be taken it be not too much fwell'd, nor extended mal a propos, in which Cafe it becomes flat and languid.

The Word in the original Greek -srsp/ppair/?, fignifies Circum- locution.

PERIPLUS, a Voyage or Navigation round a certain Sea, or Sea Coafts.

Arrian has defcribed all the Coafls of the black Sea, af- ter having infpecled 'em in Quality of General of the Empe- ror Adrian, to whom he dedicates the Defcription under thd Title oiPeripliis of the Eux'me Sea,

PERIPNEUMONIA, in Medicine, an Inflammation of fome Part of the Thorax, properly of the Lungs ; attended with an acute Fever, and a Difficulty of breathing. See Luncs, &c.

The Peripneumonia is diftinguifh'd into vert!) true 5 and notha, fpurious.

Thefirfi is a real Inflammation of the Lungs, attended with a fymptomatical Fever, and a Cough 5 by the Former of which it is diftinguifh'd from an Afthma ; and by the latter from a Pleurify. See Asthma and Pleurisy.

Its ufual Caufes are, want of Exercife, hard Study, Sup- pression of natural Evacuations, a moift Air, or the like.

When it arifes from a Phlegmon, the Patient fpits pure Blood; when it is Erefipelatous, the Sputum is yellow, and not much tinged with reel. In this laft, the Breaft is not fo much contracted, but the Fever more violent.

The (Peripneumonia is more dangerous, tho' lefs painful than a Pleurify ; Its ufual way of going off is by Expectora- tion of well, concocted reddifh, yellow, or white Matter. The flowing of the Menfes, or any Hemorrhage, a Diarrhsea, AbfcefTes about the Ears, or other Parts, are alfo good Prog- nofticks.

The Medicines prefcribed are moftly the fame that obtain in Afthmatick and Pleuritick Cafes.

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