Page:Cyclopaedia, Chambers - Volume 2.djvu/461

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In C D fit a Convex Eye-Glafs, or in lieu thereof a Me- nifcus, having the Diftance of its principal Focus a little lar- ger than the Length of the Tube -, fo that the Point, from which the Rays diverge after Refra&ion in the Objefl-Glafs may be in the Focus. — If then the Eye be applied near to the Eye-Glafs, a (ingle Objeft will be feen repeated as often as there are Cavities in the Objeft-Glafs, but ftill dimi- nifhed.

POLYPETALOUS, in Botany, a Flower confiding of feveral Petala or Leaves. See Petala.

The Covers or Defences of Flowers confift either of a (in- gle continued Petalon, thence call'd monopetalous; or of feve- ral diftinft Pieces, call'd Polypetalous. See Flower and

MONOPETALOUS.

TheWord comes from mhJ, multum, and «i?«a«v, Vet alum. Pclypetalous Flowers are either regular or irregular.—— The Regular, according to fome Botanills, are either thole confifting of two Pieces, as the Cercea •, or of four, thence called Crofs- Flowers, as the Clove Tree; or of five, called "Umbelliferous-, as Fennel -, or of fix, as the White Lilly, thence call'd the Lilly-kind. See Umbelliferous, &c.

Thofe exceeding this Number, in any Quantity, equal or unequal, form a new Clafs of polypetalous Flowers, called the Rofe Kind ; among which are rank'd all thofe of three, four, five, or fix Pieces, whore Fruits differ fo from the reft, that 'tis required they be diftinguilh'd from them.

Such is the Flower of the Water Plantane, which tho' it has only three Leaves, yet by the Relation of its Seed

with that of the Ranuncula, is ranged in this laft Clafs.

Such, alio, is the Flower of Tormentille; which by Reafon of the Difference of its Fruit from the Siliqus or Siliculoe of

the Crofs-Flowers, cannot be ranged among them. Such

alfo is the Pink, which tho' confifting of five Pieces, yet is excluded the Clafs of umbelliferous Plants, becaufe its Fruit is not divided into two Parts. — Such, laftly, are the Flowers of fome Ranuncula's, Houfe-leek, and Anemonies ; which though they have fix Petala, yet never produce Fruits divi- ded into three Lodges, as thofe of the Lilly Kind, and there- fore cannot belong to their Clafs.

The irregular polypetalous Flowers are Co called from the odd Figure and Difpofition of their Petala, what Number of them fo ever they have.

Such are thofe of two Pieces refembling two Chaps, as in Fumitory •, or thofe of five Pieces refembling Butterflies, common to all leguminous Plants.

POLYPODY, in Botany, a Plant of the parafitaical Kind, popularly called Many-feet; of confutable Ufe in Medicine, &c. See Parasite.

There are two Kinds. Common Polypody, and Polypody

ef the Oak. The firft ufually grows on old Walls in the Country, among Mofs, &c. the latter call'd alfo Oak-fern from the Resemblance it bears to Fern, grows on the Bran- ches of that Tree, in the Places where they (hoot or fpread out, feeding on a little Earth collected there from the Dud blown about with the Wind, and water'd with the Rain.

Polypody of the Oak is much the better of the two.— It muft be chofen new, well-fed, dry, brittle, of a Tan-red without, green within, of a fweet Tafte refembling Li- quorice.

The Root is what is chiefly ufed in Medicine, being e- fteem'd Cathartic ■, tho' Dr. Quincy fays 'tis no more fo than a common 'Detergent-, in which Capacity it is much pre- ferred; in Medicated Ales againft the Jaundice, Scurvy, Obftruaions of the Vifcera, Hypochondriacks, &c.

The Word is form'd from the Greek w»m\ and nit, Foot, in regard the Root of the Plant clings to Walls and Trees, by a great Number of little Fibres like Claws.

POLYP TOT ON,inRhetorick, a Figure wherein the fame Word is repeated in different Cafes, Genders or Num- bers, i.e. with different Terminations. See Figure.

Such is that of Cicero, pro Arch. Sed pleni funt omnes li~ bri, plem fapientum voces, plena exemplorum vetujias.

POLYPUS, in Medicine, a fiefliy Tumor or Excrefcence arifing on the infide of the Noftrils, prejudicial to Refpira- tion and Speech; call'd alfo, by way of Di(tic~tinon, Polypus Narium. See Nose, Excrescence, &c.

This Ptlypus arifes by feveral Roots from the Os Cribafum, and hangs down, fometimes, as low as the Lip ; growing, Jikewife, backwards, fo as to flop the Hole of the Palate, whereby the Air and Pituita defcend out of the Nofe down into the Throat ; and by this means ftrangles the Patient.

It has it Name from the refemblance it bears to the Fifli Polypus, call'd in Esglifl>-,Pourcontrel, or many-feet.— Tho' fome derive the Name from the Refemblance its Subftance bears to that of the Polypus ; and others, from the refemblance its many roots bear to the many feet of the Fifth, &e.

If it have no Roots, or only one continued Root, it is call'd a Sarcoma; which is only a beginning Polypus. See Sarcoma.

Polypus's are chiefly found in fcrophulous or cancerous Conftltutions, along with Venereal Cafes, Ulcers, Ozaenas, &-c.— Cauftics, Caufticks, emolUent Fomentations, Extirpa-

tion, and diffeftive Powders and Lotions are the uftul R»« medies.

P o l Y p us, is alfo ufed for a morbid Excrefcence in t\. Heart ; confifting of a tough Concretion of grumous Bloolt lodg'd therein. See Heart.

Malpighi gives a very accurate Defcription of this Polype In the right Ventricle of the Heart, he obferves, 'tis ululiiy larger, and of a paler Colour like Pituita, with redifh or blackifh Streaks;-in the left Ventricle it is fmaller, blacker

and denfer. He adds, that it feems to have a fort of (W.

nihil, and appears like a Congeries of Pellicles ftretch'd over one another, which form a kind of nervous Compages.

Polypus's are frequently found upon opening the Bodies of Perfons dying apopleftic ; and are doubtlefs frequently the

occafion of fudden Death They are feldom difcover'd

till they have difpatch'd the Patient.

'Tis a difpute among Phyficians, whether Polypus's be pro- duced any confutable time before, or always immediate- ly after, Death.— Mr. Gould has an exprefs Dilcourfe in the Philofoph. Tranfatl. to evince the former.

Polypus of the Lungs. In the Philofophical Traitfacli-

ens Dr. Rob.Clarke gives us a very odd Inftance of a Patient who cough'd up, at times, feveral hundred Polypus's of the Lungs.

They feem'd to have fome Organization, and were all perfeaiy alike.— The Patient faid, tho' they hid no Life, he had frequently prefs'd a (limy matter out of the Body.

Dr. Lifter obferves, that fuch Polypus's are form'd in the remoter and deeper Branches of the Afpera Arteria, whence they are very difficult to get up.— The Patient abovemen- tion'd never brought them up till after a continued coughine of half a Day and Night.

He adds, that they are nothing but vifcous Excretions of the fmall Glands, hard bak'd in thofe Glands whofe Form they receive.— M. Bujfiere obferves, they are frequently mi- ftaken for pieces of the Blood- VelTcls or Lungs.

POLYP YRENEOUS Fruits, in Botany, are fuch as contain feveral Kernels, or Seeds. See Fruit.

They are thus call'd from the Greek »«wi, much, and 7nfMi. Nucleus, Kernel. See Polyspermous.

• POLYSCOPE,aMultiplying-Gla(s, i. e. aGlafs which reprefents one Objeft to the Eye, as if it were many ; call'd alfo Polyhedron. See Multiplying Gfo/i and Polyhedron

POLYSPASTON, Polyspast, in Mechanicks, a Machine fo denominated by Kitruvius ; confifting of an Af- femblage of feveral Pullies ; ufed for rafiing of huge Weights in a little time. See Machine.

The Word comes from the Greek «Mu, and mat ; q. d. that may be turn'd, many ways.

The Multiplication of Pullies in the Polyfpaft-on is to very goodpurpofe; it being demonftra ted in Mechanicks, that the Force required to fuftain a Weight by means of a Polyfpa/ton, is to the Weight itfelf, as Unity to the Number of Hopes, or of the Pullies; thofe P*.op;s or Pullies being fuppofsd pa- rallel to each other. See Pulley.

Hence, the Number of Pullies, and the Power being given ; the Weight that will be fulhined thereby is eafily found ; viz.. by multiplying the Power by the Weight.

E.gr. Suppofe the Power 50 Pounds, and the Number of Pullies 5. The Weight they will bilance is 250.

In like manner the Number of Pullies being given, toge- ther with the Weight fuftain'd ; the Power is found by di- viding the Weight by the number of Pullies; Thus, if the Weight be 900 Pounds, and the Number of Pullies 6, the Power will be 150.

Bechales obferves, that 'tis found by experience, that a moderate Man (landing barely en the Ground will lift 150 Pound; whence the fame Man by means of a Polyfpafim confifting of 6 Pullies, will be able to fuftain 900 Pound's.

The Power of the Pullies will be ftill exceedingly increas'd by joining feveral Polyfpaftons.

To find the Number of Pullies a Potypafion U is to confi t of to raife a given Power — Divide the Weight by the Power; the Quotient is the Number required.

Suppofe, e. gr. the Weight 600 Pounds, and the Power 150; the Pullies will be 4, whofe Diameters are to be all equal, fuppofing two of them upper and two lower, moveable on the fame common Axes.

POLYSPERMOUS, in Botany, is applied to fuch Plants as have more than four Seeds fucceeding each Flower, without any certain Order or Number. See Plant.

Thefe, Mr. Ray makes a diftinft kind of Herbs, callhg them Herbefemine nudo polyfperma ; where, by Semine -audi, is meant fuch Seeds as do not put off fpontaneoully the Inte- guments or Coverings, which they either have, or appear to have, but fall offcover'd from the Mother-Plant. See S«ed.

The Word is form'd from the Greek vakil, much, and, enptM, Seed.

Polyfpermous Herbs are fubdivided into i° Such as havea Ca- lyx or Perianthiuni, confifting either firft ot three Lea<ves,mi the Flower Tripetalous, as the Plantago Aquatica, and the Sa- gittaria, both Water-Plants ; or the Flower Polypetalous, and