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PENUMBRA-PERCEPTION

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Peony. Paonia officinalis. Large perennial herb of the natural family Ranunculaceae, native of central Europe, widely cultivated for ornament. There are numerous other species, two indigenous in California.

People's Palace. Institution at Mile End Road, inaugurated by the Queen 1887 and intended for the recreation and amusement of the inhabitants of the East End of London. It comprises technical schools, art galleries, concert halls, gymnasium, etc.

Peoria. City of P. co., Ill., on the Illinois; founded 1779. It is entered by 11 railroads, is regularly laid out and has extensive manufactures. Pop., 1890, 41,024.

Pepe, GUGLIELMO, 1873-1855. Italian officer in Spain; leader of a revolt in Naples 1820; in exile 1821-48, when he held Venice for the patriots; historian of the events in which he bore part. Peperino. Variety of tuff found near Rome.

Pepin, LAKE. Extension of the Mississippi River between Wis. and Minn., 1 m. below the junction of the St. Croix River. Length 24 m., width 2-4 m.

Pepin, or PIPPIN, "THE SHORT," 714-768. Son of Charles Martel and father of Charlemagne; became sole Duke of Franks 747; first king 752; at war with Bavarians, Saracens, Lombards, Saxons, and the Duke of Aquitania. He gave Ravenna, Pentapolis, and the duchy of Rome to the Holy See, and so laid foundation of temporal power.

Pepin of Heristal, d. 714. Founder of Carlovingian line of Frankish kings; Mayor of the Palace under several Merovingian kings; conquered Burgundy and Neustria 687; father of Charles Martel.

Pepo. Fleshy fruit, with a firm rind, composed of the thickened adnate calyx and ovary, as in the Pumpkin, Cucumber, and Melons.

Pepper. Piper nigrum.

Black Pepper (Piper nigrum).

Herb of the natural family Piper

aceae, native of India, yielding from its berries the well known condiments black and white pepper. Red Pepper is derived from the fruit of a species of Capsicum, natural family Solanaceae. Other plants produce a similar substance.

Pepper, WILLIAM, M.D., LL.D., b. 1843. Prof. Univ. Pa. since 1876, and its provost 1881-94.-His father, WILLIAM, M.D., 1810-1864, was prof. Univ. Pa. 1860-64.

Pepperbush. Shrubs of the genus Clethra, natural family Clethraceae, natives of N. and S. America, bearing odorous white flowers. The two species of the U. S. are known as White Alder.

Peppercorn Rent. Acknowledgment of tenancy when lands are let virtually free of rent; one peppercorn a year to be paid on demand. Pepperell, SIR WILLIAM, 1696-1759. Merchant at Kittery,

Pleas from 1730: looday

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Louisburg June 1745; Baronet 1746; acting Gov. of Mass. 1' 58; Lieut.-gen. 1759.

Peppergrass. Herbs of the genus Lepidium, nati family Crucifera, of wide geographical distribution; also cal Pepperwort.

Pepperidge. Nyssa sylvatica. Large tree of the natu family Cornaceae, native of swampy ground in the e. U. furnishing a valuable timber; called also Tupelo, and Bla Gum or Sour Gum.

Peppermint. Mentha piperita. Odorous herb of t Mint family, native of Europe; cultivated and introduced it wet places in America, in Mich. and N. Y. See MINT.

Peppermint, OIL OF. Oil of Mentha piperita. The oil used in confectionery and in medicine. Its essential constit ent is MENTHOL (q.v.).

Pepper-Pot. Mixed dish of meat or fish with okra a red peppers, originating in W. Indies. In Pa. tripe with dou balls and red peppers are used.

Pepper-Root. Certain species of the genus Cardamin herbs of the natural family Cruciferæ, natives of N. Americ known as Toothwort.

Pepsin. Digestive ferment of the gastric juice. As four in the market it is usually prepared from the stomach of th hog, and is employed to aid weak digestion, acting on n trogenous food only. It changes albuminoids into peptone It is used in tablets.

Peptones. Bodies containing carbon, hydrogen, nitrogen sulphur, and oxygen, produced by the action of pepsin upo albuminoids, and by the action of other similar ferments; easil soluble in water and not as readily coagulated as albumens.

Peptonized Food. Any article of food artificially d gested by means of some preparation of the pancreas. Pep tonized foods are used to afford nourishment when, from an cause, the power of digestion is impaired; e.g., during th weakness consequent upon a low fever or where there is chronic disease of the stomach. See PANCREATIN.

Pepys, SAMUEL, 1633-1703. Sec. to the Admiralty 1685-8 Pres. Royal Soc. 1684-86. His famous Diary, 1660-69, was firs pub. 1825.

Pequigny. Town of France, on the Somme, near Amien notable for a treaty, signed Aug. 28, 1475, which arranged fo king engaged to quit France on receipt of 75,000 crowns, an a 7 years' truce between France and England. The Englis to release Queen Margaret for a ransom of 50,000 more. separate treaty provided for mutual aid in case of revolt i either kingdom.

Pequots, or PEQUODS. Tribe of Indians in Conn., whic was hostile to the whites and caused several conflicts and ma sacres; nearly exterminated 1637 by a band led by John Mason assisted by Uncas and the Mohegans. More than 600 Pequot were killed: others were sold as slaves to the W. Indies.

Pera. Suburb of Constantinople, occupied by foreigner and embassies; ravaged by fire 1870.

Peræa. Palestine e. of the Jordan, or part thereof, be tween Pella and Machærus.

Perak. Malay territory held by Britain from 1874. Are ab. 8,000 sq. m., pop. ab. 200,000.

Peralta, GASTON DE, MARQUIS DE FALCES, ab.1520-ab.1580 Viceroy of Mexico 1566-67; noted for justice and humanity Constable of Navarre 1568.

Peralta, MANUEL MARIA DE, b. 1847. Costa Rican autho and diplomatist, well known at Washington 1875-78 and later Peralta-Barnuevo, PEDRO, 1663-1743. Peruvian author Perameles (BANDICOOT). See ENTOMOPHAGA. Peramelidæ. See ENTOMOPHAGA.

Per Capita. By heads; according to the number of ind viduals. See PER STIRPES.

Percentage. Process and result of reckoning by th hundred. The primary elements are the base and the rate pe cent: their product is the percentage. The base being given i units, the rate is expressed decimally.

Perception. Psychologically, process of acquiring know edge of the external world by means of the senses. The bas of perception is therefore sensation, but something more needed. The object to be perceived must not only arouse

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1154

PERCESOCES-PERENNIBRANCHIATA

perience. Perhaps the most important act in the complex process of perception is the movement of attention, which brings the sensation or the object producing it into the focus of consciousness, and allows the operation of the processes necessary to the development of perception.

Percesoces. Sub-order of Acanthopterous fishes, including the Mullets (Mugilidae), Smelts (Atherinidae), and Barracudas (Sphyraenidae). These fishes stand between the Perches and the Pikes. They have the ventral fins abdominal in position, the spinous dorsal well separated from the soft dorsal, branchial arches well developed and scales cycloid. The largest species (Mugil albula) averages 2 lbs. in wt. They come in schools to spawn in June. They feed on the mud of the bottom, having a gizzard-like stomach and an extra long intestine; but the mud is partly culled before it is swallowed; the indigestible pieces are thrown out of the mouth. A special arrangement of the pharyngeal bones acts as a filter in the throat. The head is flat and scaly, the body is of pike-like proportions, but has two dorsal fins, and the ventrals are below the pectorals. The anterior dorsal is spiny. Perceval, AMAND-PIERRE CAUSSIN DE, 1795-1871. French Arabic scholar.

Perceval, JOHN, 1680-1748. Irish baronet 1691, Baron 1715, Viscount 1722, Earl of Egmont 1733; grantee of a charter to colonize Georgia 1732.-His grandson, SPENCER, 1762-1812, became M.P. 1796, Atty.-gen. 1802, Chancellor of the Exchequer 1807, Prime Minister 1809, and was murdered.

1. Sea Bass (Labrax lupus), 2. Striped Bass (Serranus scriba), 3. Wreck
Bass (Polyprion cernuum).

The principal fishery for this species is Saginaw Bay, Lake
Huron. The white perch (Morone) belongs to the Labracida.
The sub-family Etheostominae includes the Darters, which are
considered minute perches. The SUNFISHES, q. v., (Lepomis) and
Black Bass (Micropterus) of the Centrarchidae have 3 or more
anal spines and rudimentary pseudobranchs, while the Sea Bass
(Roccus or Labrax) of the Serranida have large pseudobranchs.
These families are by some authors included in the Perch family,
here restricted to perches with 1 or 2 anal spines, and rudi-
mentary pseudobranchs (except Stizostedion).

Perchers (BIRDS). See INSESSORES.

Perchlorates. Metallic derivatives of perchloric acid.
Perchloric Acid. HClO.. Colorless, fuming liquid, very
unstable and explosive. It produces bad wounds when brought
in contact with the flesh. It is made by treating potassium
perchlorate, KCIO,, with sulphuric acid.

Percival, JAMES GATES, 1795-1856. American poet, of con-
to in the past; geologist of Wis. 1854. Clio,

Percurrent.

Midvein of a leaf when it extends to but

not beyond the apex.
Percussion. The sudden stopping of a body by impact,
from which the term has been applied to shells to be exploded
upon striking by means of a percussion fuse: the means em-
which is placed a small charge of fulminate. Explosion in
ployed to discharge the musket by a percussion cap, within
such cases is produced by the conversion of mechanical energy
into heat.

Percussion. Process in physical diagnosis, which, by
tapping various parts of the body, more particularly the chest
and abdomen, gives an indication of the physical condition of
the organs beneath by the resultant sound.

Percussion Cap.

Small copper cylinder containing fulminating powder, a mixture of 7 parts mercury fulminate and 2 parts potassium chlorate, placed in the lock of a gun to explode the charge. See FULMINATES.

Percussion Table. Apparatus used in ore-dressing, in which the pulp flows in a thin sheet over the surface of an inclined table, and is kept in agitation by a succession of blows given either at the upper end or at the side of the table.

Percy, HENRY, d. 1408. Fourth Baron of Alnwick; first Earl of Northumberland 1377.-His son, HENRY ("HOTSPUR"), 1364-1403, victor of Chevy Chase, 1388, was killed at Shrewsbury, and celebrated by Shakespeare. Others of this line were prominent in war and intrigue.

Percy, JOHN, 1817-1889. Physician in the Queen's Hospital, Birmingham, 1842-51; Lecturer on Metallurgy to the Royal School of Mines 1851-79; pres. Iron and Steel Institute 1885-87. His works on Fuel, Iron and Steel. Silver and Gold, and the metallurgy of the other metals, pub. 1869-80, are standard works, and have been tr. into French, German, and Spanish.

Percy, THOMAS, D.D., 1728-1811. Bp. of Dromore 1782. His Reliques of Ancient English Poetry, 3 vols., 1765, is an important collection of ballads, freely revised and enlarged by his own hand.

Percy Anecdotes. Famous collection, published in London, in monthly parts, 1820-23, by Thomas Byerley, d. 1826, and Joseph C. Robertson, d. 1852, who wrote under the name of Shilto and Ruben Percy.

Perdiccas. Kings of Macedonia ab.700, 454-413, and 365360 B.C.

Perdiccas, d. 321 B.C. General of Alexander, and tem-
porary regent after his death, holding his
signet-ring.

Pereda, JOSÉ MARIA DE, b. 1833.
Spanish novelist and descriptive writer.
Péréfixe, HARDOUIN DE BEAUMONT
DE, 1605-1671. Bp. of Rhodes 1649, Abp.
of Paris 1662; persecutor of Port Royal.

Peregrine Falcon (FALCO PEREGRI-
NUS). Hawk formerly used in falconry.
It is a very swift flyer. It is known to
have attained a speed of 150 m. an hour.
The male, called Tercel, is smaller than
the female.

Pereiopod. One of the walking legs of the lobster and of allied Crustacea.

Pereira, JONATHAN, M.D., F.R.S., 1804-1853. Practitioner and prof. in London. Materia Medica, 1839-40; Diet, 1843. Pereira da Silva, JOAO MANOEL, b. 1817. Brazilian historian.

Pereira de Figueiredo, ANTONIO,
1725-1797. Portuguese priest of the Ora- Hooded Peregrine on the
tory. He tr. the Bible and wrote much
against the Jesuits.

In Russia,
Perekop, ISTHMUS OF.
connecting the Crimea with the mainland
of European Russia. It is crossed by a
ship canal.

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block.

One end of the leash is attached to the jesses, the other to a ring driven into the side or top of the block; and thus the hawk is prevented from escaping.

Père-la-Chaise. Cemetery in e. Paris; named from the Jesuit confessor of Louis XIV., whose garden was converted into this burial place 1804.

Perennial. Vegetable structures which endure indefinitely, year after year.

Perennibranchiata (PROTEIDA, SOZOBRANCHIA). Tribe of Ichthyoidea (Urodele Amphibians), including forms having

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Mud-Puppy (Necturus maculatus).

living in subterranean waters, having three toes on the fore feet, two on the hind feet, and only two pairs of gill slits; and the Necturus or Menobranchus (known popularly as the Mudpuppy or Water-lizard), with four-toed feet and four pairs of gill slits, abundant in the Great Lake region and Upper Mississippi system.

Perennichordata. See COPELATE.

Perez, ANTONIO, 1539-1611. Sec., agent, and scapegoat of Philip II. of Spain. Tried for the murder of Escovedo, emissary of Don John of Austria, he confessed under torture, escaped to Aragon, was there repeatedly delivered by popular risings, and fled to France 1591. Relaciones, 1598.

Pérez, José JOAQUIN, b. 1801. Pres. of Chili 1861-71. Pérez, SANTIAGO, b. 1830. Colombian author and Senator, twice Minister to the U. S.

Pérez de Hita, GINES. Spanish author. His Civil Wars of Granada, 1595-1604, a mixture of history and romance, has been drawn on by other writers, from Calderon to Irving.

Pérez Galdós. See GALDÓS.

Perfect. Flowers which contain both stamens and pistils. Perfection, IN ETHICS. Excellence of human nature considered as a rational end for moral action.

Perfectionism. Doctrine professed by many Methodists, some Roman Catholics, and others, that man may through grace attain a sinless state in this life. It is disowned by most Christians.

Perfectionists. Sect founded 1838 in Vt. by J. H. Noyes; transferred 1847 to Madison co., N. Y., and known as the Oneida Community.

Perfect Square. Quantity whose two equal factors can be exactly expressed.

Perfoliate. Sessile leaves having the stem on which they are borne passing through the lower portion of their blades. Perforata. Section of Foraminifera, including the orders TEXTULARIDEA, CHILOSTOMELLIDEA, LAGENIDEA, GLOBIGERINIDEA, ROTALIDEA, NUMMULINIDEA (q.v.).

Perforata. Division of the Madrepore corals. See MADRE

PORARIA.

Perforated Cake Powder. Used in heavy guns; hexagonal powder prisms having seven perforations from upper to lower base; made by moistening and reworking ordinary grained powder of sp. gr. 1.5 and subjecting it to a pressure of ab. 65,000 lbs. per sq. in. in hexagonal molds. Each prism weighs ab. 555 grs. and has sp. gr. ab. 1.7. Combustion proceeds from interior perforations on increasing surface, and the amount of gas evolved is better proportioned to perform its work with less initial pressure on the bore than in the case of single grained powder.

Perforate Shell. Gastropod shell with a hollow colu

mella.

Perfumery. Art of preparing essences and perfumes. A good perfume should leave no residue on evaporation. Some of the most exquisite perfumes are obtained from the most

offensive substances: the oil of pineapple being produced from

Restoration of the great Altar Building at Pergamus, by R. Bohn. art in 2d century B.C. Its library of 200,000 vols. was give to Cleopatra by Antony, and added to that of Alexandria. I ruins were excavated 1878-86, and many sculptures were take to Berlin.

Pergolesi, GIOVANNI BATTISTA, 1710-1736. Italian compos of the Neapolitan school, best known by his opera La Ser padrona, 1733, and a Stabat Mater for two women's voic with accompaniment of strings.

Perham, SIDNEY, b. 1819. M.C. 1863-69; Gov. of Main 1871-74.

Peri. In Oriental Mythology, a Being, harmless or bene cent, and immortal, but not to be admitted to Paradise; mo familiar through Moore's poem.

Peri, JACOPO, ab. 1600. Florentine musician, one of th creators of the lyric drama (see OPERA). He composed th opera Euridice, performed at the marriage of Henry IV. France.

Periander, ab.665-585 B.C. Tyrant of Corinth. Perianth. Floral envelopes of a flower, especially in cas where the calyx and corolla are indistinguishable, or where or of them is wanting; sometimes called Perigone.

Periastre. That point in the orbit of a binary star whe the secondary star approaches nearest to the primary.

Periblem. Layer of cells at the growing points plants, which develops the bark; immediately beneath th epidermis.

Peribranchial Space. Space surrounding the bra chial sac in Tunicates, etc.

Pericambium. Layer of thin-walled cells, found in th roots of dicotyledonous and gymnospermous plants, immed ately within the endodermis; periphlæum.

Pericarditis. Inflammation of the pericardium. Fr quently a sequel to inflammatory rheumatism. It is ofte accompanied by a dropsy of the part, known as hydroper cardium.

Pericardium. Serous sac enveloping the heart, enablin its movements to be carried on without undue friction. See SEROUS MEM

BRANE.

Pericarp. Seed-vessel of flowering plants; ripened ovary-wall.

Perichætium. Cluster of modified leaves which surrounds the archegones in the flower of a moss.

Perichondrium. In Embryology, membranous investment of dermis which surrounds the cartilaginous cranium and becomes ossified about it to form the membrane bones.

Pericladium. Expanded and sheathing base of a petiole, especially in herbs of the Carrot family.

Pericles, ab.495-429 B.C. Greatest statesman of Athens. He entered public life 469, and by the ostracism of Thucydides 444 was left without a rival.

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1156

PERICLINIUM-PERIPTERAL

Periclinium. Involucre of the compound flower or Anthodium of the Composite; also known as Periphoranthium.

Periderm. Hard cuticular layer developed in the coenosarc of certain Hydroids.-In Botany, the tissue formed externally from the phellogen of stems. Its diminutive is peridiolum.

Peridium. Investing membrane of the puff-balls, truffles, and other fungi, consisting of several layers of densely matted hyphæ; also corky layer of the bark in exogenous stems. Peridot. See CHRYSOLITE.

Periodicals. Magazines and reviews, usually pub. monthly or quarterly; numerous of late in all civilized lands, and occupying a middle place between newspapers and ordinary books. The Royal Society's Transactions began 1665, the Journal des Savants also 1665, and the Gentleman's Mag. 1731.

Periodic Function. One in which the same value recurs at regular intervals in the change of the variable. Periodic Law. In Chemistry, the properties of the elements are periodic functions of their atomic weights. Periodic Table. Arrangement of the chemical elements in groups and series, in the order of their atomic weights, their atomic weights. Such tables have been arranged by Mendeleéff and by Lothar Meyer. Peridotite. Group of basic igneous rocks containing showing the relation of the properties of the elements and olivine, but no feldspar.

Perienteron. Blastocol cavity after the digestive cavity is established in embryos.

Perier, CASIMIR, 1777-1832. French Deputy 1817; Finance Minister 1828-29; Premier 1831. His policy was that of the Juste Milieu.

Périers, JEAN BONAVENTURE DES. See DES PÉRIERS, BONA

VENTURE.

Perigastric Cavity. Perivisceral cavity; body cavity outside of the alimentary canal.

Perigee. Point of the moon's orbit nearest the earth. Perigenesis. Theory of heredity, according to which protoplasm is made up of small bodies called plastidules, each of which is an organized system of molecules, each molecule having a peculiar form of vibration; the character of the whole is determined by the forms of these vibrations. The vibrations are complex and run through cycles so as to return periodically to the same phase as a result. The plastidule also undergoes a cyclic change of its powers. Changes in the environment modify the vibration systems, and also determine the resultant effective work of the molecule in adding other molecules, or of the plastidule in splitting into new plastidules, for growth is the one and cell-division results from the other. A modification of the system of vibrations constitutes variation, and must always be impressed from without. Thus Hæckel accounts for the cyclic development of ontogeny and the branched development of phylogeny. As to the branched development of the differentiation of tissues, he supposes a similar modification of the vibration along different lines, as each cell divides, due to environment. Development is a purely mechanical process, capable of being represented mathematically and graphically. See WEISMANN'S THEORY OF HEREDITY. Perigone. See PERIANTH.

Perigonium. Walls of a sporosac or reproductive bud in Medusoids. When mature there are three layers, a middle, mesotheca, an outer, ectotheca, and an inner, endotheca.

Perigueux. City of France, 42 m. s.e. of Angouleme, the ancient Vesunna of Cæsar's time. Here are the remains of a Roman amphitheater. It has an archæological museum rich in inscribed stones. Pop., 1891, 28,000.

Perigynium (PERIGYNE). In Botany, sac which incloses the pistil and achenium in the genus Carex; also perichætium of Bryophytes.

Perigynous. Stamens inserted around the pistil of a flower, either on the calyx or corolla; also, disk of a flower when adnate to the base of the calyx.

Perihelion. Point in a planet's or comet's orbit nearest
the sun.

Perimeter. Bounding line of a plane figure.
Perimeter. Instrument used for determining the area of
the field of distinct vision of the eye.

Perineum. In Regional Anatomy, the lowest part of the
trunk found between the joining of the thighs to the trunk.
Perinium. Third layer of cells existing on the spores of
certain Jungermanniacea, often beautifully sculptured.

Period. In simple harmonic motion, interval of time between two successive passages of the vibrating body through a given point of its path in the same direction.

Period. In Mathematics, two or more consecutive digits of a number, considered together.

Periodates. Salts derived from periodic acid, HIO,, or
from derivatives of normal periodic acid, I(OH),.

odic Acid. HIO.. Simplest form, made by treat-
odine: white crystals, containing

Period of Sun Spots. Discovered by Schwabe of Dessau. It is not absolutely constant, but is approximately 11 years in length. The last maximum epoch was 1895.

Pericci. People of the native race in Lacedæmon, whose ancestors occupied before the Dorian conquest; regarded by the Spartans as inferiors, but not generally oppressed.

Periostitis. Inflammation of the periostium. It is most frequently experienced in the membrane investing the roots of the teeth; dental periostitis.

Externally it affords a Periostium. Sheath of fibrous tissue enveloping bones, except over the articular surfaces. surface to which the muscles can be attached; internally it serves to give nourishment to the bone and to regenerate the bony tissue, should it be destroyed.

Periostracum. Epidermal layer on outside of shells of

mollusks.

Peripatetics. Disciples of Aristotle. See LYCEUM.
Peripatus. See ONYCHOPHORA.
Periphloëm. See PERICAMBIUM.

Periphoranthium. See PERICLINIUM.

Periphyllida. Family of Peromeduse, including Jellyfish of complex structure, with twelve tentacles, of which four

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containing thirty-two pockets.
are interradial and sensory, and with sixteen marginal lappets,

Periphyses. Sterile filaments of the nature of paraphyses arising from the hymenium of certain Fungi at places where there are no asci.

Periplasm. Layer of hyaline protoplasm surrounding the oösphere in the oögones of Oomycetes, a sub-class of Fungi. Periplast. See BLASTEMA.

Periplus. Voyage or circumnavigation. That of Hann was along the w. coast of Africa to a point beyond the Senegal Periproet. Space surrounding the anus, especially i Echinoderms.

Peripteral. In Grecian Architecture, this denotes a tem ple entirely surrounded with columns.

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PERIPYLEA-PERMANENT FORTIFICATION

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in the edge of which is a mouth leading into a pharynx. Th
opposite pole of the body is adapted for fixation.
a typical example.
Vorticella

Perivisceral Cavity. Part of the body cavity that su rounds or contains the viscera.

Peripylæa. Order of siliceous Radiolaria, with a spheri-
cal structure to the central capsule which is uniformly perfo-
rated. The nucleus is single in the Monocyttaria, and double
in the Polycyttaria. The sub-order Sphærida includes Haliom-
ma, with the spherical skeleton partly in the central capsule.
The sub-order Discida has the skeleton somewhat flattened;
Thalassacolla has no connected skeleton. The Polycyttaria
consist of colonies of Radiolarians fused by their extra capsu-
lar protoplasm, e.g. Collosphæra.
Perisarc. Chitinous envelope secreted about certain Hy- spring; native of Eu-

droids.

Perischoëchinidæ. See TESSELLATA.

Periscopic. Eye-glasses when in the form of converging
or diverging menisci. These were proposed first by Wollaston
to replace the ordinary double convex and double concave
lenses, because by this means a much wider range of vision is
obtained: hence the name periscopic glasses.

Perisome. Integument of echinoderms.
Perisperm. See ALBUMEN.

Perisporangium. Indusium of ferns.

Perispore. In Algology, cell in which tetraspores are

formed.

Perissad. In Chemistry, element whose valency is expressed by an uneven number.

Perissodactyla (ODD-TOED UNGULATES). Hoofed Mammals, having the middle toe or digit most developed and serving as the main support of the body. In all, the toes of the hind feet are odd in number, one or three digits being present (in Coryphodon five). When horns are present, they are never supported by a bony core, and are in the median line of the skull even when there are more than one. The stomach is not divided into compartments. There are never less than 22 dorsolumbar vertebræ. The dentition is usually complete. A space is present between the incisors and premolars; the canines, when present, are developed, especially in the upper jaw of the males, into tusks. The families included are Coryphodontidæ, Rhinocerotida. Tapirida, Brontotherida, Palæotherida, Macraucheniidæ, Equida.

Peristaltic Motion. Action of the muscular coat of the intestines by which the contained substance is moved on regularly.

Peristerite. Variety of albite feldspar, showing a peculiar iridescence, similar to the colors on the neck of a pigeon; sometimes used as a gem-stone.

Peristeromorphæ. See COLUMBINE.

Peristoma. 1. Lip of the aperture (mouth) of snail-like shells. 2. Region around the mouth of animals, having a circumoral ring of cilia or of tentacles. It includes the space thus inclosed.

Peristome. Row or rows of hair-like processes, called teeth, surrounding the mouth of the sporange or capsule of certain mosses. These teeth are in number always some mul

tiple of 4.

Peristyle. Inclosure of columns surrounding either a
building or a vacant space. It is most commonly employed
to denote a circle of columns, but is equally applicable to a
rectangular arrangement.

Perithecium. Conceptacle which contains the asci in
Ascomycetes, an order of Fungi.

Peritoneum. Serous sac covering the contents of the
abdomen and lining the abdominal walls. Because of the
diverse contents of the abdomen, it is the most complexly
formed of all the serous sacs.
movement of the various organs in the abdomen. See SEROUS
Its use is to permit the proper
MEMBRANE.

Periwinkle.

Vinca minor. Low, blue-flowered, trailing

shrub of the natural
family Apocynaceae,
blooming in early

rope; much cultivated
as an ornamental
plant.

Periwinkle (LITTO-
globular snail of sea-
RINA). Medium-sized
shores; it feeds on Algae.

Periwinkle, PENNY WINKLE, WINKLE, WRINKLE (SYCOTYPUS). Large sea snail, with hairy epidermis; it sometimes destroys oysters.

Perizonium. Wall of the auxospore in Diatoms.

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Periwinkle (Vinca minor).

Perizonius, or Voorbroek, JACOB, 1651-1715. Prof. Franeker 1681, Leyden 1693; writer on the classics. Origines Babyloniæ, 1711.

Perjury. Willful false swearing to evidence material to the issue in a legal action. The definition and punishment vary with the statutes of different jurisdictions.

Perkins, BISHOP W., 1841-1894. Judge 11th Dist. Kan. 1873-83; M.C. 1885-91; U. S. Senator 1892-93.

Perkins, CHARLES ALLEN, 1832-1892. U. S. Minister to Portugal 1869-70; married to a Spanish princess 1870; proscribed in Spain 1874.

Perkins, CHARLES CALLAHAN, 1823-1886. American writer on art. Italian Sculptors, 1868-83.

humorist.
Perkins, ELI (MELVILLE D. LANDON), b. 1840. American
Eli Perkins (at large), 1875.

Perkins, ELISHA, 1741-1799. Inventor 1796 of an alleged method of curing rheumatism by "metallic tractors," which was used in London, and caused much controversy; inventor also of an antiseptic drug for other diseases, which failed to save himself when tried for yellow fever.

Perkins, GEORGE HAMILTON, U.S.N., b. 1836. Lieut. 1861; distinguished at New Orleans and Mobile; Captain 1882. Perkins, GEORGE ROBERTS, 1812-1876. American mathematician, author of widely-used text-books.

Perkins, JACOB, 1766-1849. American inventor of improvements in banknote engraving, and later of the bathometer, the pleometer, and the steam-gun. He was in England from 1818.

Perkins, JUSTIN, 1805-1869. American missionary in Persia from 1834; translator of the Bible into Syriac. Perlitic Structure. rocks. See PEARLSTONE.

Structure seen in some vitreous

Perm. City of e. Russia, on the Kama, at the mouth of the Joga Shika. It has extensive smelting works. Pop., 1890, 39,281.

Permanent Fortification. Defensive works erected Peritonitis. Inflammation of the peritoneum; of many during peace for the protection of vital strategical points, forms and from many causes. such as an important harbor, the capital of the State, or other denly with agonizing pain. The sufferer lies on his back with Acute peritonitis begins sud-point essential to the security of the State. They require the shoulders raised and thighs flexed to relax the abdominal walls. The pulse is small and wiry, the abdomen tense and tympanitic. Physicians are divided as to the treatment: some insist upon free catharsis, others upon the free use of opium, and still others say an incision through the abdominal walls and local treatment is necessary. The probability is that all are correct, and skill is required to determine the proper treatment in the individual case.

Peritreme. Peristome of a Gastropod shell.

application of the highest development of the art of fortification, and are intrusted to the care of trained military engineers. In the U.S. the principal harbors on the Atlantic and Pacific coasts are permanently fortified, while in European States the frontiers and capitals are also necessarily cared for. The recent developments in artillery have greatly modified the character of these works and made obsolete the masonry structures which in 1860 were considered abundantly strong. In that day the 64 lb. solid shot could make but little impression upon the 8 ft. of granite wall, but the ton and

shot of the 17 :

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