Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/278

 POL

POL

Compound ftructure than might at firft be imagined ; there may always be obferved, round the edges of this part, a fen- ftble motion, refembling that of an indented wheel, or rather that of a fcrew turned very nimbly about. Thefe, tho' they approach to the fhape of the clutter -polypes, and refemble them in their having this motion about their mouths, yet never h«ve any tendency to form clufters, but are ever found loofe and fingle. There are always a number of little round bodies,

■ which f.cm to be animals of a very minute Size Iwimming about in the water in which thefe polypes live ; and thefc are continually drawn into the mouths of the polypes, and ferve them for food.

The manner of thefc creatures propagating themfelves, is very amazing; they do it by dividing their own body into two ; but this is not done longitudinally, as in the clufter-^/#«, nor tranfverfely, but diagonally from the edge of the head to the oppofite edge of the tail ; lb that of the two thus formed out of one, the one has a head and no tail, the other a tail and no head ; but thefe deficiencies are foon made up, and the head foon grows ou' of one, and the tail out of the other. Mr. Tremblcy, in his account of this infect, calls that of the two which has the old head, the fuperior p'djpe ; that which has the old tail the inferior. The firft particulars pbfervaMe in a funnel-polype that is going to divide, are the lips of the in- ferior polype, or thofe transparent edges that are fo very con- spicuous in the creature when perfectly formed. Thefe new lips firft discover themfelves upon the polype that is going to divide, from a little below the old lips to about two thirds of the length of the polype, reckoning from the head : but thefe new lips are not difpofed in a (trait line, according to the length of the polype, but run Hoping near half way round about. Thefe lips are diftingu'ifhed by their motion; but it is to be obferved, that this motion is at firft very flow, and requires an attentive eye and good glafles to difcover it. Phil. Tranf. N° 474. p. t8c.

That portion of the body of the pdype, which is bounded by thefe new lips, then gathers up itfelf, and thefe lips infenubly draw clofe together, and finally they ctofe themfelves. By this means there is formed a Swelling at the fide of the polype, which is found, on a clofe examination, to be the head of the new p'lype, bounded by the lips before-mentioned. Before tins Swelling is become very remarkable, it is eafy to difcover the true polypes that are forming themfelves; and after this, when the fwelling is greatly increafed, thefe two diftinct ani- mals will be found joined to one another only by a very fmall part of their bodies. The Superior polype, in this cafe, no ■longer adheres to the inferior one but by its pofterior extre- mity, which is ftill fixed on one fide of the inferior one. The fuperior one then begins to make motions, which tend to the Separating itfelf from its fellow ; and thefc foon finiih the work, and he becomes perfectly difengaged, and Swims away whi-

■ ther he pleafes, and foon fixes on Some other place. T he in- ferior polype remains fixed in the place where both were be- fore, and becomes a perfect animal ; and the fuperior one. after taking a tour in the water, fomctimes returns to the old place, and fixes htmfelf by the tail to the body of the inferior ■one. All thefe animals are extremely minute, and are not to be feen distinctly, much lcfs are their operations obferved with out the help of glafles ; and as there is no taking them out of -the water to bring them before the microfcope in the common way, without abfolutely deftroying them, Mr. Trembley, who has obferved them with more accuracy, than perhaps any ■other perfon ever did, has contrived to view them in a glafs veffel, in their own water, by bringing them So near the fides of the glaiTes, that the microfcope glaffes are able to reach them properly from the outfide. The fubftances on which they are fixed, are to be brought clofe to the edges of the veflel, by means of a fet of quills framed properly togethi and the microfcope glafles to be Supported on a moveable arm made for that purpoie. Phil. Tranf. N° 474. p. 183.

//^•-Polype. See Veh-P lype.

POLYPODES, a word ufed by fomc as a name for the mille- pedes.

POLYPODITES, a name given by the antients to a wine im- pregnated with polypody, and fometimes for the juice of mil- lepedes, cxprefied with wine.

POLYPODIUM, poypody, in the Linnasan fyftem of botany the name of a genus of the capillary plants, comprehending the polyprdium and knclrtis of Tournefort ; the lonehitis of Linnzeus beii'g a very different genus of plants. The cha- racter of the polypod'-wn is, that the fructifications are difpofed in round Spots on the under part of the difk of the leaf. The characters of this genus, according to Mr. Tournefort, arc thefe : The flowers are not difenvered, but the Seeds srow on the back of the leaf: thefc are contained in membranace- ous capfules, of aroundifh figure, which are placed togethe: in chillers, and have nothing round them, as thofe of the tri chomanes have, but are left to be burft by the contraction of their own fibres

The polypodies are not branched, but confift of Single leaves divided almoft to the middle rib into oblong jag^s or Seg- ments.

The Species of po'y^ody, enumerated by Mr. Tournefort, are thefc : 1. The common polypody, z. The common great

polypody, with Serrated leaves. 3. 'Thetefthr polypody. 4. The large polypody, with pointed leaves. 5. The broad thin-leaved polypodv, called by Muntingius, and others, Senfitive polypody. 6. The narrow-leaved polypody, commonly called lovchitis af- pera, and rough jplecnwort. 7. The Welch polypody, with leaves jagged at the edges (if the pinnules. 8. The finely divided African po/ypedy. 9. The great golden polypody. 10. The polypody with Slen.Ier creeping roots, n. The finely di- vided black p'lyp'.dy. 12. The polypody with leaves like the afplcnium. 13. The thin-leaved pendulous polypody. 14. The polypody with pointed and rigid pinnules. 15. The pendu- lous polypody, with a reddifh hairy down. 16. The Smooth pendulous polypody. 17. The lcaft pendulous polypody. j8. The curled polytody, refembling the dvtrieh's feathers. 19. The rough dentated polypody. 20. The flender undulated po- lypody. 2 1 . The curled polypody, with cups, z 2. The Sweet polytody, with the tafte of liquorice. 23. The polypody co- vered with Silvery Scales. 24. The brown finely Serrated po- lypody. 25. The pellucid polypody. 26. The polypody with bluifh punctated roots. Town. Inft. p. 54c. The common polypody is the kind ufed in medicine ; it is ufual- ly found about the roots of old trees,, in woods, and by hol- low road fides. There is a vulgar opinion, that Such of it as grows upon the ftump of an oak, is preferable to what grows on any other tree ; but there is no foundation for this. The root is the part ufed in medicine ; it is a gentle cathartic, and is particularly recommended in diforders arising from ob- structions of the liver and fpleen. It is by many eStee'7 ed an excellent medicine in Scorbutic aiid hypocondriac com- plaints. The country people take it in infufion alone, hut phv- ficians ufually prefcribe it in compound decoctions and medi- cated ales. It has alfo been made an ingredient in many of the purging electuaries in the old difpenfatories,

POLYPOSIA, a term ufed by the antients to exprefs a copious drinking of wine.

POLYPUS (Cycl.)— Polypus, the polype, in zoology. Seethe article Polype.

Polypus, in natural hiftory, a name given by fome of the ear- lier writers to the thin-fuelled, nautilus, or nautilus papy- raceus. The body and arms oS this creature Somewhat re- Sembling thofe of the polype, it was fuppofed to be a Species of polype inclofed in a Shell, which it could quit occasionally, and go on more to feed.

Polypus, in medicine. — Mr. Le Dran cured a polypus of the nofe, which he could not extract wholly, in the Sollowing manner, which may be practifed for deftroying all fuch ex- crcScences. He introduced one end of a large Seton, put nn the point of the fore-finger of the left hand, into the patients mouth, till he brought it behind the velum pendulum ; then Aiding a pair of thin crooked forceps into the affected noftri), he catched hold of the feton, after covering what was to be introduced into the nofe with a Suppurant medicine. While he drew the cord, he endeavoured to preferve the velum pen- dulum from being hurt, by introducing his finger into the mouth, and fupporting the cord upon it. He continued the Suppurant till he was Senfiblc, by the patient's breathing free- ly through the noflril, that the remains of the polypus was de- stroyed, and then he injected deficcatives to cauterize the ulcer. Le Dian, Tom. 1. obf. 6. ap. Med. ESS. Edinb. Though Kcrkringius, and others, have endeavoured to ex- plode the notion of the formation of true polypi in the heart and blood veSTels, yet Malpighi, Bartholine, TuJpius, Peck- lin, and others, have given us inconteftable inftances of the existence of true polypi in the heart, in the ftrictcft fenfe; and we have three unquestionable evidences of the like nature, in Phil. Tranf. N° 464. Sect. 6.

POLYSACT1NODOS, in natural hiftory, a name given by Linkius, and fome other authors, to thole ftar-fifh whofe bo- dy is divided into more than five rays, that being the more ufual and general number,

POLYSCHlDkSfucus, a fea-plant, a\\ted in EngWih fea-banger. It is one of the largcft Sea-plants we know, growing often to ten foot or more in length. Its root is not fiat in the manner of moft of the other fea-plants, but is compofed of feveral little hooks, all which lay fail hold of the ftonc on which it grows : theSe, in Some meafiire, refemble the tendrils of the vine, and are Somewhat broad and flatted at the end, where they are fattened to the ftonc, tho' round elfewhere, and are about half an inch long : thefe hooks grow from a broad flat- tifii part at the bottom of the ftalk, which is often four or five inches in diameter, and is ufually hollow, being com- pofed only of two membranes confiderably tough and firm, with a cavity between them ; Srom the center of this rifes the ftalk, which is oSten twilled and undulated at the edges ; from the top of this ftalk grows the leaf, which is divided into eight or ten Segment.; each of whi h is often again divided into two '! hefe foments are very Ions; and as the plant floats in the water, give it much of the appearance of a broad piece of leather cut into feveral thongs : thefe all terminate in fharp points, and rrieir colour is a brownifh green. The niccft eye cannot difttnguifh the Jeaft nerve or fibre, either in the ftalk or leaf of this plant ; but on great numbers of thefe plants, that curious enquirer Mr. Reaumur, found flowers of the fame kind with thofe which he originally difcovered on

the