P I T
P L A
feem deftined to feparate a finer juice than is neceflary for the nourifhment of the coarfer parts of the tree. It is obferved of plants which have a larger than ordinary fhare of pith-, that they produce larger quantities of flowers than others ; inftances of this are feen in the rofe, the lilac, and the com- mon elder : and in the femlaceous plants, the quantity of flowers is not only profufely large, according to the great quantity of pith in their italics, but the pith feems carried up the ftalks all the way to the feeds themfelves ; the long feeds of the fweet myrrhis, and other the like plants, while not ripe, being only pith. Mem. Acad. Scienc. 1709. P1THECAI.OPEX, the femivufpa, or ape-fox, a name given by Aldrovandus and fome others, to that ftrange American ani- mal which we call the opojjum.
The name is compounded of that of the fox and the ape ; of the natures of both which animals it is fuppofed by fome to participate. See the article Opossum. PITHIAS, orPiTHiTEs, with fome writers, a fort of comet, or rather meteor, in form of a tub. Of thefe it is faid there are divers kinds, viz. fome of an oval figure, others like a tun or bar- rel fet perpendicular, and fome like one inclined, or cut fhort off"; others having a hairy train or bufh, C3r. PITHYUSA, in botany, a name ufed by many authors for a
fmall fpecies of fpurge. See the article Tithymalus. PITUINA, in the materia medica, a name for the refin of the
pitch-tree. PITYIDES, a name ufed by fome authors for the kernels in- clofed in the cones of the fir or pitch-tree ; they are recom- mended by the old phyficians, in diforders of the breaft. PITYLiSMA, a name of one of the exercifes prefcribed by the antient phyficians, as of great fervice in chronic cafes. It confuted in a perfon's walking on tip-toe, and ftretching his hands as high above bis head as he could, keeping the whole body alfo as much upon the ftretch as might be. In this condition the patient was to walk as far as he was well able, all the while moving about both hands as much as he could, in all directions. PITYRIASIS, a name given by the antients to a fcurfy difor- der of the head and eye-brows, and of any other part where there is hair. It makes the {kin feem as if covered with bran, and is attended with a troublefomc itching. PIVA, in the Italian mufic, a hautboy, or a cornet. Seethe
articles Hautboy and Cornet, Cycl. PLACAGNODUUGIA, in natural hiftory, the name of a genus of fpars.
The word is derived from the Greek «-x«|, acruft, «V«> pure, and wauy»s, pellucid.
The bodies of this genus are cryftalline terrene fpars, or fpar- ry bodies with much of the brightnefs and tranfparenoe of cryftal, but debafed by an admixture of earthy matter. are imperfectly pellucid, and formed into thin plates with flat furfaces, but covered at times either in part or entirely, with tubercles or botryoide prominences, and are compofed of ar- rangements of oblong concretions, of no determinately an- gular figure.
Of this genus there are only two known fpecies, tho' theft vary fo much at times in figure, that they might lead an in- accurate obferver into imagining there were many diftinct fpecies of each. 1. A hard femi-pellucid and yellowifn brown one. This is found in many parts of England ; in fome places encrufting over the fides of fiffures of ftone, and others coating over vegetable bodies in fprings, &ff. 2. A brittle pellucid and whitiih one, found on the fides and tops of our fubterranean caverns on Mendip hills and elfewhere. and in form of aroundifhball, feemingly compofed of threads, in the neighbourhood of Efperie in Hungary. Hill's Hift. of Fofl* p. 342. PLACAGNOSC1ERIA, in natural hiftory, the name of a ge- nus of fpars.
The word is derived from the Greek nA«|i a cruft, «y*&s, pure, and sTKitpor, opake.
The bodies of this genus are dull and opake cryftalline ter- rene fpars, formed into crufts, and of an irregular and not ftriated texture within.
Of this genus there are three known fpecies: 1, A hard whitiih brown one, found very frequently on the roofs and fides of caverns on Mendip hills, and in other parts of Eng- land. 2. A dull crumbly whitiih one, found in many parts of England, encrufting the fides of caverns, and of fifliires of ftone. And 3. A dull pale brown friable one, of a very coarfe texture. This is the moft common of all the bodies of this genus, and is found in variety of forms, among other;, encrufting the fides and bottoms of our tea-kettles, and other veflels, in which water is frequently boiled. Hill's Hift. of Fofl*. p. 34.6. PLACE (Cycl.) — Place is ufed in the doctrine of artificial memo- ry:and thefe^/^jmaybeeitherfuchin a proper fenfe, as a door, a window, a corner, tsrY. or familiar and known perfons ; or any other thing at pleafure, providing they be placed in a certain order, animals, plants, words, letters, characters, hiftorical perfonages, c5V. tho' fome of thefe are more and fome lefs fit for the purpofe ; but fuch kind of places greatly help the memory, and raife it far above its natural powers.
Bacon's Works Abr. Vol. II. p. 474, 475. See the article Memory, Cycl. and Suppl. FhACE-bricks. See making of Brick,,
PLACENTA (Cycl.) — The placenta has generally been looked upon as an original part among the fecundines ; but accord- ing to Dr. Thomas Simfon of St. Andrews, it feems to have no place in the ovarium, nor in the uterus, till once the ovum becomes contiguous to the fundus, and then every contiguous part becomes really a placenta. He thinks the fundus uteri a place peculiarly fitted for the growth of the placenta, as pro- per foils encourage the growth of the roots of trees and fhurbs many of which are propagated by the branches however placed - fo that every part of them feems equally fitted to be root or branch. Hence he thinks extra uterine conceptions can have no placenta ; and he fays, there are no inftances in authors to 'contradict his opinion. See Med. EfF. Edinb. Vol IV Art. r 3 . ' '
The placenta does not increafe in the fame proportion which the fcetus does : for the (mailer the fcetus is, the placerta is proportionally Jarger. Monro, in Med. Eft. Edinb p ia.z bom Ruyfcb. * "
The placenta generally adheres to, or near the fundus of the womb, and is covered on the fide next to the womb, with a fine membranous continuation of the chorion. Vid. Monro Medic Eft". Edinb. Vol. II. p. 128. and the authorities there quoted.
The feparation of the plac-enta from the womb muft produce abortions, and this may be occafioned by different caufes ope- rating in various manners, and requires very different treat- ment to prevent the lofs of the fcetus. See Monro, in Med. Eff. Edinb.Vol.II. Art. 11. or it's Abridgment, Vol. I. p 398* feq. ' *" '
Placenta, in botany, a term improperly given by Mr. Houf- ton, in the Philofophical Tranfa&ions, N° 421, to 'what is ufually called receptacle. See Rzcxpt aculvm femimtm.
Placenta, in natural hiftory, the name of one of the clafles of the echini marini. The characters of thefe are, that they are of a deprefled or flatted form, and are wrought in vari- ous ftiapes, as the paftry people make their cakes ; they all have a cinquefoil flower at their top, and their mouth is in the middle of the bafe ; the aperture for their anus is ufuaUy near the edge. See Tab. 8. N° g, 10.
Of this clafs there are three genera : 1. The mellita. 2. The laganum. And 3. The roiula. Which fee under their" feve- ral heads. Klein's Hift. Echin. p. 30.
Placenta, among the antients, a kind of cheefe-cake, the moftfimple kind of which was made of flower mixed with oil and cheefe, to which honey was added : but the more luxurious fort of people added likewife a great variety of herbs and fruits, as ahofugar, eggs, butter, &c. Pitifc. Lex. Antiq. in voc.
PLAGIAULOS, «%o7ia(Aet, among the antients, a kind of flute.
PLAGIOPLATEUS, in natural hiftory, a term ufed by Ar- tedi and others to fignify deprefled, in oppofition to the term eathetoplateus, ^ which fignifiescomprefled. See both explained under the article Ca t he topl ate us.
PLAGIUM, in natural hiftory, the name of one of the ^reat clafles, or families of fifties. The characters of whidfare, that the tail is placed horizontally. They refpire by means of lungs, and have ufually a double fiftule in the head. They are viviparous, and the males have a penis and teftes, the fe- males the vulva, ovaria, mamma, & c . and they brincr up their young with milk. &
The term is derived from the Greek nxtzyw, tranfverfe and Siij**, a tail. Vid.7te#,Gen.Pifc. Linnai Svftema Nature P- 3 [ -
PLAGUE (Cyd.)~ Dr. Dover fays he cured the plague among fome failors, in a voyage, by one very plentiful bleeding to the quantity of an hundred ounces, and with drink fharpen- ed with fpirit and oil of vitriol. Med. Eft. Edinb.
PLAIN (6>/.>— Plain furface, in geometry, that which lies evenly between its bounding lines ; and as a right line is the fhorteft extenfion from one point to another, fo a plain fur- face is the fhorteft extenfion from one line to another.
PLAISE, in ichthyology, the Englilh name for the fifli called by authors plate fa and pajfer lavis,hy fome quadratulus. It is, according to the Artedian fyftem, a fpecies of the pleu- ronedtes, and is diftinguiflied by that author by the name of the pleuroncftes with fmooth fides, and with a fpine near the anus, and the eyes and fix tubercles placed on the right fide of the head. This name carries a diftinftive charader with it ; and it were to be wimed that we had fuch names in com- mon ufe among authors for all the fift that are known to us. See Pleuronectes.
PLAN (Cyd.) — Plan of a baflion, in the military art, is the fame with the face of a bajlion. See Face.
PLANE-/™*, plaianus, in botany, the name of a genus of trees, the characters of which are thefe : The flower is of the amen- taceous kind, and is of a glomerated fhape, and compofed of a great number of ftamina with their apices. Thefe flowers are barren, and the embryo fruits are found on other parts of the plant ; thefe finally become larger, and contain feveral feeds winged with down.
The
