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duced into Britain is not exactly known. The distinction of introducing it is ascribed with most evidence of accuracy to Evelyn, who in his Sylva (published 1664) mentions having received cones and seeds from the mountains of Libanus,' while describing the beauties of the tree and speaking of its probable adaptability to the English climate. Aiton in Hortus Kewensis makes 1683 the date of planting the celebrated Chelsea cedars, which are assumed by some to have been the first trees planted in England. There are many fine specimens of the Lebanon cedar in different parts of Britain, notably at Sion House, Goodwood, and Enfield in England, and at Hopetoun, Dalkeith, and Beaufort in Scotland.

The Deodar, or Himalayan Cedar (Cedrus Deodara), a tree held in great veneration by the Hindus, and of which the name is properly Devadara (divine tree'), is common in the Himalaya mountains at elevations of 7000 to 12,000 feet, forming magnificent forests, and attaining a great size, a height sometimes of 150 feet, with a trunk 30 feet or more in circumference, an ample head, and spreading branches. It and the cedar of Algiers (C. Atlantica or Africana), found in the mountainous regions of the north of Africa, are but sub-species or varieties of the Cedrus Libani. The wood of the deodar is resinous, fragrant, compact, and very durable. It is susceptible of a high polish, and in its polished state has been compared to brown agate. Owing to the abundance of resin, laths of it burn like candles. Its turpentine is very fluid, and although coarse, is much used in India for medical purposes; and tar and pitch are obtained from the trunk. The deodar has now become very common as an ornamental tree in Britain, although few specimens have yet attained a very considerable size. -The name cedar is often given to other coniferous trees besides the true cedars. Thus, the Siberian Stone Pine, or Cembra Pine, is called the Siberian Cedar (see PINE), and a species of fir (Abies religiosa) is the Red Cedar of California (see FIR). A species of Cypress (q.v.) is known as White Cedar, and another as the Cedar of Goa. Several of the trees which bear the name cedar are species of Juniper (q.v.), among which are the Virginian Cedar, or Red Cedar of North America, and the Bermuda Cedar-which yield the cedar-wood used for pencils -the Spanish Cedar of the south of Europe, &c. The name cedar is even given to trees which have no resemblance to the true cedars except in the resinous quality of the wood; thus the Cedar-wood of Guiana is produced by Icica altissima, a tree of the natural order Amyridaceæ (q.v.); the cedar of the West Indies (see next article) belongs to the natural order Cedrelacea; and the name Bastard Cedar is given in India to a tree of the natural order Byttneriaceae (q.v.).

Cedar, BARBADOES, is strictly speaking Juniperus bar idensis; but a more important tree is that called Bastard Barbadoes Cedar (Cedrela odorata), a tree of the order Cedrelaceæ (q.v.). Its wood has an agreeable fragrance, and being soft and light, it is used for canoes and for shingles. Havannah cigar-boxes are very generally made of it, and in France it is used in making black-lead pencils.

Cedar-bergen, a mountain-range in Cape Colony, stretches north and south on the east side of Olifant River Valley, in Clanwilliam division, and has plantations of Cape cedar (Widdringtonia juniperoides), which are now, however, being fast destroyed. This is the only locality where this species is found. Sneeuwkop (6335 feet) is the highest point of the range.

Cedar Bird. See WAXWING.

CEILING

Cedar Creek is a river of Virginia, U.S., which gives name to a battle fought 19th October 1862, when the Federals under Sheridan defeated the Confederates under Early.

Cedar Rapids, a town of Linn county, Iowa, on the Red Cedar River, 79 miles SW. of Dubuque. large flour-mills, carriage and machine works, and It is an important railway centre, and has several breweries. Pop. (1860) 1830; (1890) 18,020.

Cedilla (Sp., Fr. cédille, It. zediglia; from zeta, the Greek name for z, because it has taken the place of z in such words as leczon, mod. leçon, a mark placed under the letter c (ç), especially in French, where it is desired to give c the sound of s before the vowels a, o, u.

Cedrate. See CITRON.

Cedrelaceæ, a sub-order of Meliaceæ (q.v.), all tropical or subtropical trees or shrubs, with pinnate leaves, mostly valuable for their timber-e.g. mahogany, satin-wood, toon, Barbadoes cedar, the yellow-wood of New South Wales, &c. The barks of some species are febrifugal. See MAHOGANY, CEDAR (BARBADOES), &c.

Cefalù, a town of Sicily, on the north coast, 40 miles ESE. of Palermo. It is situated at the foot of a lofty promontory (1235 feet), with old Greek and Saracenic remains. It has a cathedral, marble-quarrying and fishing. a port, and 12,714 inhabitants, chiefly engaged in

Ceglie, a town in Southern Italy, 21 miles NE. of Taranto. It has a trade in grain, oil, and fruit. Pop. 13,865.

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Ceiling (Fr. ciel; Lat. cœlum, 'heaven '). This term seems to have been suggested by the use of arched coverings for churches, and even for rooms, which prevailed in the middle ages, and were frequently painted blue and decorated with stars. Arched ceilings among the Romans were known by the name of camera, and were formed by semicircular beams of wood, at small distances from each other, over which was placed a coating of lath and plaster. But the ceilings most commonly in use amongst the Romans were flat, the beams, as in modern times, having been at first visible, and afterwards covered with planks and plaster. Sometimes hollow spaces were left between the beams, which were frequently covered with gold and ivory, or paintings or patera-large flowers such, for instance, as are used in the panels of the vault of the Pantheon. The oldest flat ceiling in existence is believed to be that of Peterborough Cathedral. Like that at St Albans Abbey, it is made of wood. Ceilings of churches in the middle ages were generally painted and gilded in the most brilliant manner; and many existing ceilings still exhibit the traces of early decoration of this kind. In French churches the ceilings are generally vaulted, but in England they are more The older ceilings generally usually of wood. follow the line of the timbers of the roof, which, in the Early English and Decorated, are often arranged so as to give the shape of a barrel vault. In ceilings of this description there seldom are many ribs, often only a single one along the top. In the Perpendicular style, the ceiling often consists of a series of flat surfaces or cants, formed on the timbers of the roof. Though sometimes altogether destitute of ornament, they are more frequently enriched with ribs, dividing them into square panels, with bosses (see Boss) or flowers at the intersections. Wooden ceilings are sometimes formed in imitation of stone-groining, with ribs and bosses, examples of which will be found at York, Winchester, and Lincoln. In the Elizabethan age ceilings were generally of plaster, but they were ornamented with ribs having bosses or

CELAKOVSKY

small pendants at the intersections. It is not unusual for the ceiling immediately over the altar, or the roodloft, to be richly ornamented, whilst the rest is plain. See ROOF.

Celakovsky, (1) FRANZ LADISLAUS, Bohemian poet, born in Strakonitz, 7th March 1799, died at Prague, professor of Slavonic Philology, 5th August 1852. His principal works are Echoes of Russian and Bohemian Folk-songs (1833-40), and a cycle of love-songs and didactic and political poems (1840). He also translated the works of Herder, Goethe, and Scott.-(2) LADISLAUS, botanist, born in

Prague, 29th November 1834, was appointed professor of Botany there in 1880. Besides several monographs on particular genera, he has published a general book on the Bohemian flora (3 parts, 1867-75) and an elucidation of the Darwinian theory. Celandine is the popular name (and corruption) of Chelidonium majus, a perennial papavera

Celandine (Chelidonium majus): a, a flower.

ceous herb, which, although not Britain, is doubtfully indigenous.

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uncommon in Its pretty foliage and umbels of small yellow flowers, which bloom from May to August, might alone attract attention, but its ancient repute among herbal ists is due to its yellow milky juice, which is very acrid and poisonous. Ex ternally it was applied to warts and ulcers, and internally administered, it was supposed to be a specific for jaundice, apparently on no better warrant, however, than that drawn from its colour by the 'doctrine of signatures.' Its old English name Swallow-wort, which appears to be almost a translation of the botanical one, seems founded on a supposed association between the beginning and ending of its flowering time and the arrival and departure of the swallows.-It is, however, the LESSER CELANDINE which is more familiar to general readers, at least since Wordsworth devoted no fewer than three poems to its honour. This is Ranunculus Ficaria, also known as the common fig-wort or pile-wort, a quite unre

Lesser Celandine (Ranunculus Ficaria).

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lated ranunculaceous plant, which grows in abundant patches in fields and coppices, and brightens them in early spring with its plentiful golden flowers. Its tuberous roots and swollen separable buds give it additional botanical interest, while it is also noteworthy that these results of peculiarly vegetative habit are associated with a frequent imperfect maturity of the pollen. See REPRODUCTION.

Celano, LAGO DI. See FUCINO (LAKE OF).
Celastraceæ. See SPINDLE-TREE.

juato, on the Rio Laja, about 150 miles by rail Celaya, a town in the Mexican state of GuanaNW. of the city of Mexico, has several fine plazas, and woollen cloths and saddlery. Pop. (1877), handsome churches, and manufactures of cotton with district, 28,336. The burning of its bull-ring, on Easter Sunday 1888, caused considerable loss of life.

Cele'bes (in England usually pronounced Ce'lebes), the third largest and the central island of the Eastern Archipelago, from 1° 45' N. to 5° 37' S. lat., and from 118° 49′ to 125° 5' E. long.; about 800 miles long by 200 broad; total area estimated at 76,260 sq. m. It is practically a Dutch possession, though there are numerous small native states. In configuration, it consists of a central nucleus whence radiate four long mountainous limbs, respectively E., NE., SE., and S., inclosing the three gulfs of Gorontalo, running in nearly 200 miles, Tolo 150 miles, and Boni about 200 miles. The gulfs, as also the north and west coasts, are studded with islands, rocks and shoals, and larger outlying islands. Of the central nucleus and the two inner limbs little is known. The east end of the eastern peninsula (north end of island), Minahassa district, is subject to earthquakes, and contains 11 volcanoes, some of them active, such as Mount Sapoetan (5938 feet), and, farther east, Mount Klabat (6559 feet), which has now, however, long been quiescent, besides numerous hot springs and sulphur lakes. The mountains of the south peninsula, essentially a limestone formation, seldom rise above 2000 feet. In the extreme south, however, are Maros (4225 feet) and Bonthain (9994 feet). The uplands of the south peninsula are well wooded, but its vegetation is much less luxuriant than that of the east peninsula. Between the hills and coast of the south peninsula are extensive grassy plains, affording pasture for large herds of cattle, and for the horses for which the district is famous.

Celebes is rich in lakes, among them, Passo, in the central nucleus, 35 miles by 25 miles, and Tondano, nearly 2000 feet above the sea. There are numerous streams, but Celebes, no part of which is more than 50 miles from the sea, offers no space for the formation of large rivers. The Sadang, rising near lake Passo, flows due south for nearly

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120 miles.

Thanks to the elevation of the land and its seaexposure, Celebes enjoys a comparatively cool and healthy climate. The vegetation includes rice, maize, coffee, sugar, tobacco, indigo, areca, betel, pepper, clove and nutmeg growing wild; the tree yielding macassar oil, oak, teak, cedar, ebony, sandalwood, bamboos; also the upas. Minahassa,. the most highly cultivated district, 60 by 20 miles, has coffee plantations, producing coffee of a remarkably fine flavour, entirely in the hands of the government, and where alone the culture system' has been applied in its integrity since 1822. Many animals, birds, and insects are wholly peculiar to Celebes-a tailless baboon, two kinds of cuscus, the babiroussa, and Sapi-utan, three kinds of starlings, two magpies, &c. Gold is obtained from surface washings, principally in Minahassa and Gorontalo districts; iron in the districts bordering the Gul

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of Tolo. Salt is also abundant. Tin and copper are likewise worked.

The population of the island of Celebes is given at 1,000,000, who may all be regarded as belong. ing to various Malay stocks, except 7000 Chinese and 2500 Europeans. The Bugis (see BONI) and Mangkassars of the south peninsula, tall, shapely, and comparatively fair, are the dominant native race, much disposed to trading and seafaring. The Alfuros,' a collective name for the other native tribes, are at a very low grade of culture. Celebes was first visited in 1525 by a Portuguese expedition from the Moluccas. In 1607 the Dutch began to trade with Celebes, and now claim the whole island, which they have divided into the residencies of Macassar and Menado, a third division round the north and west of the Gulf of Tolo being included in the residence of the Ternate. The total value of the exports in 1884 was £600,000, of which coffee formed nearly a half; and the im: ports in the same year, £465,714. The women of Celebes weave the sarang, or national garment, which, together with variegated mats, is largely exported. A high-road' skirts the coast of the south peninsula from Mandale, 30 miles N. of Macassar, to Balang-Nifra, on the Gulf of Boni; elsewhere are only ordinary roads and footpaths. The chief town is Macassar, with a sea-frontage of nearly 2 miles. Menado, the capital of Minahassa district, and seat of a Dutch resident, is described as the prettiest settlement in the whole of the Dutch East Indies, and has a pop. of 2500. See Lahure, L'ile de Célèbes (Paris, 1879).

Celery (Apium), a widely distributed genus of Umbellifer. The common celery (A. graveolens) is found wild in Britain and most parts of Europe, in ditches, brooks, &c., especially near the sea and in saline soils, and is acrid and uneatable. In cultivation, however, abundant nutrition has greatly mollified its properties, and two principal forms have arisen-one in which an abundant development of parenchyma has taken place in the leafstalks; the other in which it affects the root-while these again possess their sub-varieties. The former sort is the common celery of British gardens, where the familiar long blanched succulent stalks are produced by transplanting the seedlings into richly manured trenches, which are filled up as the plants grow, and finally raised into ridges over which little more than the tops of the leaves appear; and a supply is thus insured throughout the whole winter. The other form is the turnip-rooted celery, or celeriac, and is now largely cultivated on the Continent. Both forms are eaten uncooked alone, or in salads, or in soups, or as a boiled or stewed vegetable, and are pleasant and wholesome, although when used too freely or frequently they are diuretic and aphrodisiac. Some authorities identify celery, instead of the closely related Parsley (q.v.), as the Apium with which victors in the Isthmian and other games were crowned, and of which the Greeks were also wont to twine their sepulchral garlands.

Céleste, MADAME, dancer, was born in Paris 6th August 1814 (by her own account), more prob. ably three or four years earlier. A pupil at the Conservatoire, she early showed remarkable talent. She made her début in 1827 at New York, and during her residence in America married one Elliott, who died early. At Liverpool in 1830 she played Fenella in Masaniello; in 1831-33 she became extremely popular in London. Her second visit to America (1834-37) is said to have brought her £40,000. After her return she took part successively in the management of the Theatre Royal, Liverpool, and the Adelphi and Lyceum in London. Her imperfect English long confined her to non

CELIBACY

speaking parts. She retired from the stage in 1874, and died at Paris, 12th February 1882.

Celestine, a mineral bearing the relation to Strontium (q.v.) that heavy spar bears to barium. It is essentially sulphate of strontia, SrOSO,, with occasional admixture of sulphate of baryta, carbonate of lime, oxide of iron, &c., in small proportions. It much resembles heavy spar, but is not quite equal to it in specific gravity; is usually blue, often of a very beautiful indigo-blue; sometimes colourless, more rarely reddish or yellowish. Its crystallisation is rhombic, like that of heavy spar. Most beautiful specimens of crystallised celestine are found in Sicily. Celestine derives its name from its colour. It is the source from which nitrate of strontia, employed in the manufacture of fireworks, is derived.

of whom filled St Peter's chair in 422-432 (see Celestine was the name of five popes, the first POPE). The most notable was the Neapolitan Peter di Morrone, who after a long life of ascetic severities was much against his will elected pope as Celestine V. in 1294, when he was nearly eighty years of age. He resigned his office after five months- the great refusal,' for making which he is placed by Dante at the entrance of hell. He was died in 1296. He was founder of the Celestines, imprisoned by his successor, Boniface VIII., and and was canonised in 1313.

Celestines, an order of hermits of St Damianus, founded by Peter di Morrone about 1254, and confirmed as a monkish order by Urban IV. in 1264 and by Gregory X. in 1274. They called themselves Celestines when their founder ascended the papal chair. They follow the rule of St Benedict, wear a white garment with black hood and scapulary, and live a purely contemplative life. In the 13th and 14th centuries the order spread rapidly through France, Italy, and Germany, but subsequently decayed, and is now almost extinct. The French Celestines were secularised by order of Pope Pius VI. in 1776-78; so also were the Neapolitan Celestines.

opposed to the first and strongest natural law (Gen. Celibacy (from cælebs, unmarried'), a state i. 28), has from a variety of causes come to be regarded in certain religious systems as a condition of the most sublime self-sacrifice. The perpetual celibacy of the priests of Isis, and the chastity nowhere was this sentiment so strongly and widely of the vestal virgins, are familiar instances. But manifested as among the millions devoted to the religion of Buddha. The theories of oriental philosophers and the natural tendency of mystics did not fail to influence the early Christian churches, and led before long to the doctrine that virginity is a state in itself more excellent and more holy than Roman Church at least, imposed celibacy upon all the married life, and to the discipline which, in the priests and sacred ministers. The Old Testament is remarkably free from any tendency to exalt celibacy above matrimony. But although texts may be quoted on either side, the germs of the doctrine in question may be discovered in the New Testament. St Paul affirms it to be good for a man not to touch a woman,' and wishes that all men were celibate like himself (1 Cor. vii. 1, 7). Christ himself speaks mysterious words in commendation of those who have made themselves eunuchs for the kingdom of heaven's sake;' and the Lamb is followed on Mount Zion by 144,000 virgins, first-fruits unto God and unto the Lamb' (Rev, xiv. 1-5).

The apostolic writings, however, while they suggest the excellence of virginity in general, supply no ground for the law of clerical celibacy. In the first epistle to Timothy, the deacon as well as

CELIBACY

the bishop is told he must be the husband of one wife, and rule his household and his children well; and forbidding to marry' is reckoned among the doctrines of devils.' But a remote sanction for the later discipline has been sought for in the regulations of the Jewish priesthood. The Mosaic law forbade priests to marry divorced women or harlots, and enjoined continence upon all when preparing to offer sacrifice. Jerome argues that the Christian priest should offer sacrifice daily, and should therefore be perpetually continent; and Pope Siricius (385 A.D.) insists that marriage was permitted to the priest of the old law only because the sacerdotal order was then limited to the tribe of Levi, but now that the tribal restriction is removed, the license is abrogated also.

The ecclesiastical legislation on celibacy was developed gradually and unequally in the several parts of the church. In the 2d century it became a pious custom to make vows of chastity, and it was thought becoming in the higher clergy to renounce matrimony; and although there are examples of bishops and priests in the first three centuries living with their wives and begetting children, it has been confidently asserted that no instance can be quoted of a marriage contracted at this period after ordination. The obligations of the marriage contract were, however, considered sacred; and the Apostolic Canons impose the penalty of deposition on bishop, priest, or deacon, who should separate from his wife under the pretence of piety. At the end of the 3d and beginning of the 4th century, marriage after ordination was prohibited by formal legislation. A further and important step was taken in the year 305 by the Spanish council of Elvira, which decreed that sacred ministers who were already married, should live in continence. At the Council of Nicæa an attempt was made to impose this new rule upon the whole church, but it was frustrated by the opposition of a venerable monk, Paphnutius, himself a celibate; and the law to this day has never been accepted in the Eastern Church. In the West, however, a series of synodal enactments and papal decrees established or renewed the more rigorous ⚫ rule. But in no matter of ecclesiastical discipline must the distinction between theory and practice be more carefully observed. The clergy everywhere resisted the law, and resisted with considerable success. St Patrick, who tells us that his father and grandfather were in holy orders, when laying down rules in one of his Irish synods for the conduct of his clergy, directs that their wives should keep their heads covered.' In the province of Milan, indeed, the marriage of priests continued to be perfectly legal. Discipline and usage varied in different countries, but it may be safely said that for many centuries the celibacy of the uncloistered clergy was little more than a pious fiction, until Hildebrand, afterwards Gregory VII., by his great influence and vigorous measures, secured a more strict observance of the rule.

From the 12th century (first and second Lateran Councils) a great change took place in ecclesiastical law. The marriage of priests was now declared to be not only sinful but invalid. It became henceforward difficult for any priest to justify his marrage on the plea that the prohibition of such marriage was abrogated by custom, or not binding under supposed exceptional circumstances. The clerical consorts became no longer wives but concubines; and, further, the priest who went through the marriage ceremony was held to commit a far greater crime than if he had contented himself with simple fornication. Yet in spite of all this the law was to a large extent set at defiance. In many parts of Europe it was a common thing for benefices to pass from father to son. Influential bishops obtained letters of legitimation for their

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children, and provided for them out of the property of the church. Avaricious princes and prelates made traffic of the concubinage of the lower clergy by levying a species of blackmail, under the name of fines, on the tacit understanding that the focaria, or occupant of the priest's hearth, should not be disturbed. At the time of the Council of Trent, the Emperor Charles, in the expectation that some relaxation would be made in the laws on the subject, permitted in 1548, by the arrangement known as the Interim, married priests to retain their wives until the council should come to a decision. The Emperor Ferdinand a little later (1562) urged upon the same council the abrogation of celibacy. But the Catholic reaction was too strong, and the council in November 1563 pronounced, If any one shall say that clerks constituted in holy orders, or regulars who have solemnly professed chastity, are able to contract matrimony, or that, being contracted, such matrimony is valid. . . let him be anathema.'

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It should be observed, however, that in the United Greek Church Rome tolerates a married clergy— i.e. a man already married may be ordained priest, and continue to live with his wife, though continence is imposed upon him at certain times. It is the custom for the young candidate for orders to leave the seminary for a while to get a wife, and then return for ordination. If he should become a widower, he cannot of course marry again, and no married priest can be made a bishop. The bishops are therefore, as a rule, taken from the monasteries.

Since the Council of Trent, the observance of celibacy has been comparatively well maintained. This is especially true of those countries where the Catholic community is mixed with or surrounded by Protestant neighbours, and watched by a vigi lant press. Away from the high-roads of civilisation, in Mexico, Brazil, and other parts, concubinage has again become the rule, less openly perhaps, but quite as obstinately as in the middle ages.

The moral loss or gain to the church from her discipline in this matter is a question of controversy which from time to time has been raised within her own communion. But the attention paid by biologists to the hereditary transmission of human faculties and dispositions has recently exhibited the effects of celibacy in a new light. Mr Galton has remarked that the Roman Church has acted as if she aimed at selecting the rudest portion of the community to be alone the parent of future generations.' The policy which attracts men and women of gentle natures fitted for deeds of charity, meditation, or study to the unfruitful life of the cloister and the priesthood, appears from this point of view to be singularly unwise and suicidal,' tending, as it must, though by imperceptible degrees, to the deterioration of the race. To the enforcing of this discipline in Spain, for example (coupled with the cutting off of independent thinkers by the Inquisition), Mr Galton attributes much of the decadence of the country during the last three centuries. In France, where the most promising lads of the village are successively picked out by the parish priest for the bishop's seminary, the process of elimination must in the long run tell upon the general character of the population. In small Catholic communities, again, where the priestly vocation is held in high esteem by the educated classes, and where mixed marriages are discountenanced, a similar result cannot fail to occur. The controversial literature on the matter is abundant. The most complete treatment of the subject, from the historical point of view, will be found in Sacerdotal Celibacy in the Christian Church, by Henry C. Lea (Philadelphia, 1867). See also MONACHISM.

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Cell, a unit-mass of living matter, whether rounded off by itself, as in the simplest plants or animals and in the youngest stage of all organisms, or associated with other cells to form a higher unity. The great majority of the Protozoa and Protophyta are single cells, and all other organisms begin where the former leave off. From the double unity resulting from the fusion of two sex-cells the higher plants and animals develop by repeated division, and they may be therefore always resolved into more or less close combinations of variously

Fig. 1.-Dividing Egg-cell (after Gegenbaur).

modified unit-masses. In most cases these individualities of the simplest order are minute, and their separateness is not to be discerned with the unaided eye, but there are many instances among the simplest plants and animals, as well as in the component elements of higher forms, where the unit-masses are relatively giant-cells and quite visible without the use of the microscope. The giant Amoeba Pelomyxa, the common sun-animalcule Actinosphærium, the Alga Botrydium, and some of the cells (e.g. bast) of plants may be noted as illustrations of cells with considerable dimensions. In the great majority of cases the body of the cell includes a well-defined centre or nucleus; and the definition may therefore be extended in the statement that a cell is a nucleated unit-mass of living matter or protoplasm.

I. History. In the article BIOLOGY it has been pointed out that a more and more penetrating scrutiny alike of structure and of function led naturalists from organs to tissues, and from tissue to cell. Some of the steps in this gradually deepening analysis deserve fuller record.

Discovery of Cells.-In the latter half of the 17th century the simple microscope afforded to Malpighi and Leeuwenhoek, to Hooke and Grew, what was literally a vision of a new world. In applying their rough and simple instruments to the study of the structure of plants and animals they became pioneers in the investigation of the infinitely little. Leeuwenhoek (Phil. Trans. 1674) seems to have been the first to observe, what are now so familiar, single-celled organisms. In the 18th century Swammerdam and others continued with much enthusiasm to describe the minute intricacies which their new eyes' revealed; Fontana (1784) observed the kernel of the cell-the nucleus-and some of the elements of the tissues; but the foundation of scientific histology was not laid until the appearance in 1801 of the Anatomie Générale of Bichat. In this epoch-making work organs were resolved into their component tissues, and their functions were interpreted as the sum-total of the properties of their constituent elements. Such a conclusion was the utmost that could be reached with the appliances then at command.

Early in this century, however, an improvement in the appliances of observation furnished a fulcrum for a new advance. Fraunhofer discovered the principle of achromatic Lenses (q.v. ; also ACHROMATISM); these were combined into the compound Microscope (q.v.), and a new era began. Fibres and 'globules,' 'laminæ,' nuclei,' and even 'cells were described. In 1831 Robert Brown emphasised the normal presence of the nucleus discovered by Fontana, and made the first important advances in the study of the vegetable cell. Isolated discoveries,

such as that of the nucleolus by Valentin (1836), occurred in rapid succession during those years. Dujardin in 1835 described the sarcode or living matter of the Protozoan Foraminifera and of some other cells, and thus emphasised, as Rösel von Rosenhof had done many years before (1755) in regard to the 'Proteus animalcule' or Amoeba, the most important element to be considered in forming a true conception of the cell. The importance of his description, of which he was apparently himself unconscious, had for some time the same fate as that of his predecessor of almost a century before. Observations had in fact to accumulate before any generalisation became possible. The first definite steps towards a co-ordination of results was probably that of Johannes Müller, who in 1835 pointed out the resemblance between the cells of the vertebrate notochord and the elements observed in plants. The cellular nature of the epidermis and the presence of nuclei therein was next ascertained, and similar discoveries were made in regard to several other tissues. Up to 1838 there was in fact a period of research in which cells were observed rather than understood.

Establishment of the Cell-theory.-As early as 1826 Turpin had maintained that plants were formed by an agglomeration of cells. Professor M'Kendrick well points out, what one would of course expect, that for some years before 1838 botanists were beginning generally to recognise the cellular composition and origin of plants. The conclusion known as the cell-theory was doubtless vaguely present in many minds. Its definite statement was still awanting. In 1838, however, Schleiden proved that a nucleated cell is the only original component of a plant embryo, and that the development of all tissues might be referred to such cells. In the following year Schwann published at Berlin his famous Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals (Trans. Sydenham Society, 1847). In this classic work it was shown that all organisms, plants and animals alike, are made up of cells, and spring from cells. In composition and in origin there is unity. The generalisation familiarly known as the cell-theory was thus clearly established, and though now a commonplace and postulate of histology, it may fairly be described in Agassiz's words as the greatest discovery in the natural sciences in modern times.' Following up the generalisations of Schwann and Schleiden, come a host of researches by which the essential advance contained in the cell-theory' was more and more fully confirmed. Cells were not only observed, their import was recognised.

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New Conception of the Cell.-When the cell-theory was established, the general conception of the cell was far from being either accurate or complete. It was usually described as a vesicle closed by a solid membrane, containing a liquid in which float a nucleus and granular bodies. It was also the general opinion that such cells originated within a structureless ground substance. In two ways these notions were speedily corrected. On the one hand as regards the origin of cells, Prevost and Dumas (1824), Martin Barry (1838-9), Reichert (1840), Henle (1841), Kölliker (1846), Remak (1852), showed that in the case of the egg-cell, and in the growth of tissues, each new cell arose by division from a predecessor. This important conclusion was most firmly established by Goodsir in 1845, and Virchow in 1858, who proved that in all cases, normal and pathological alike, cells arose from preexisting cells, a fact expressed in the axiom omnis cellula e cellula. In the second place it gradually became apparent that too much importance had been attached to the cell-wall and too little to the contained substance. Referring details to the

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