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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 marriage 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 clergyi.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 vigilant 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.

To

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. 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 Bichât. 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.

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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 (see LENS, MICROSCOPE); these were combined into the compound microscope, 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.

The

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. 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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and active nature. In accordance with the growth of the cell it may occupy a position distinctly nearer one of the poles. Accumulations of fat or mucus may push it passively to the side. Or it may actively change, in response to hidden forces of attraction between it and the surrounding protoplasm, in the case of some ova exhibiting a peculiar rotation, or else distinctly shifting its ground from the centre towards the periphery.

Structure. In many cases, as Leydig especially has shown, the nucleus seems to lie in a nest of its own, in a clear space within the surrounding cellsubstance. Nor is it in many cases at least de

A, Embryonic cells from growing point of a root; B, older cells finitely insulated from the surrounding protoplasm, becoming vacuolated. (After Sachs.)

bubbles of water engulfed along with the foodparticles, round which the protoplasm, shrinking | from contact, often forms a definite contour. In other cases they are more permanent, and represent minute reservoirs of secreted substance, cisterns of by-products in the vital manufacture of the cell. Finally they may be seats of special activity, where, perhaps, under the stimulus of irritant waste-products, the protoplasm exhibits spasmodic contractions and expansions, and forms the so-called 'contractile vacuoles,' which in alternate dilatation and bursting often seem to serve to remove fluid from the living matter to the exterior.

(c) Nucleus.-In the great majority of cells a central body of definite composition and structure is present which appears to be essential to the life and reproduction of the unit-mass. In many cases the nucleus is well concealed, but as more skilful staining has revealed its presence in many cells which used to be described as non-nucleated, it is rash to conclude too certainly as to its absence in any particular case. Thus some of the Monera, which were formerly defined as the simplest of simple animal organisms without even a nuclei, have been shown to possess them, and the line of division separating Protozoa into Monera and Endoplastica has therefore been removed. Furthermore, the researches of Gruber have shown that in some of the higher Protozoa (ciliated Infusorians) where the nucleus seems entirely absent, dexterous staining prove its diffused presence in the form of numerous granules which take on the characteristic nuclear dye. Yet in some cases, such as the young spores of some Protozoa, the greatest care has not yet been successful in proving the presence of the nucleus. In contrast with these cases, many cells exist in which the nucleus is represented not by one, but by many bodies the so-called polynuclear state. A further reserve requires to be made, that it is to a large extent an hypothesis that all such definite central inclosures should be slumped together under the one title of nucleus. It is rather probable that in this, as in other organic structures, we have to do with various degrees of development and definite

ness.

fications occur.

In the form also of the nucleus numerous modiIn the majority of cases, indeed, it is more or less spherical, but it may be elongated, curved, horseshoe-shaped, necklace-like, and even branched. In the young stages of some ova it is like the entire cell, somewhat plastic, and is pulled in and out in amoeboid movements. In special conditions, furthermore, the nucleus may exhibit peculiar deformations. It is in fact a peculiarly sensitive and all-important part of the cell, suffering with it in degeneration, changing with it in growth and division.

In position the nucleus is typically central, where as the presiding genius of the cell it shares and perhaps controls the general protoplasmic life. But it frequently suffers displacement both of a passive

but is moored to the latter by strands which have intimate relations with both. As of the entire cell, so of the nucleus it must be said that in the great majority of cases it is very far from being homogeneous. According to Hertwig, Schleicher, Schmitz, Brass, and others, homogeneous nuclei may indeed occur, but if they do they are rare, and it must always be remembered that the nucleus has its history, and may be less complex at one time than it is at another. To Flemming (1882) above all is due the credit of having elucidated the complexity of the nucleus, and the labyrinthine structure to which he showed the clue, and to which Frommann |(1867) had many years previously directed special attention, has been studied and restudied by scores of expert histologists during the last six years (1888). While their results disagree abundantly on minor points, two conclusions stand out clearly -(1) that the nucleus has a structure like that of the general cell, consisting of firmer framework and of more fluid intermediate substance, and (2) that apart from detailed difference there is throughout the world of cells a marvellous unity of structure and process, in the nucleus in repose and in the nucleus in action.

In the nucleus the following parts have to be distinguished: (1) The readily stained firmer threadwork, (2) an intermediate clear substance filling up the interstices, (3) definite and usually globular formations known as nucleoli, (4) various granules, and (5) a limiting membrane or nuclear wall. These may be briefly touched upon in order.

(1) The Nuclear Framework (reticulum, trabecular framework, &c.).-A mere statement of the different descriptions given of this important part of the nucleus would carry us far beyond the limits of this article. The most marked difference of opinion is this, that some describe the framework as distinctly of the nature of a network, while others are as emphatic in calling it a much-coiled band. A third party unite both views, and regarding the nucleus as variable, describe a reticulum at one time and a coiled filament at another. Thus, according to Flemming, Pfitzner, Retzius, Leydig, Van Beneden, &c., the nuclear framework is typically a reticulum; according to Strasburger, Balbiani, and Korschelt, a twisted ribbon is the only or most frequent form; according to Brass and Rabl, both types may equally occur. A further complication has been emphasised by Zacharias, Pfitzner, Carnoy, and others-this, namely, that besides the readily stained threadwork noted above (the so-called chromatin), whether this be in the form of a reticulum (Pfitzner) or of a coiled ribbon (Carnoy), there exists another-not readily stained

framework of achromatin. This had indeed been recognised though not insisted on by the first series of investigators. To sum up, it is now generally allowed that the framework or threadwork of the nucleus may exist as a network or as a coil, and that it is in a sense double, consisting of readily stainable chromatin on the one hand, and unstainable achromatin on the other. It need hardly be added that as there is considerable diversity of

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CELL

opinion as to whether given nuclei have a netted or coiled framework, there is yet greater variety in the minuter description and figuring. According to Flemming the network is quite disorderly, but Rauber, Leydig, and others have described distinct

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Fig. 3.-(After Carnoy):

B

A, Cell and typical nucleus: a, slight membrane; b, radiating protoplasmic network; c, wall of nucleus; d, plasma of

nucleus; e, nuclear coil.

B, Nucleus at rest, showing network.

C, Nucleus before division, showing coiled filament.

radial structure; according to some the nuclear coil is endless, while others describe it as divided into portions; and when we descend to such subtleties of observation as the intimate structure of the threadwork or the relations between chromatin and achromatin, the diversity is so great that it seems desirable here to leave such minutiæ untouched.

(2) The Intermediate Nuclear Substance.-Besides the nuclear elements of definite form, whatever that form may precisely be, all investigators describe an intermediate substance of variable consistence, usually semi-liquid, amorphous and structureless, but with fine granules. It is a clear unstainable plasma' filling up the chinks, but nothing definite is known as to its composition. (3) The nucleolus which lies within the nucleus varies greatly in size and position, and more than one are very generally present. Flemming has defined them as portions of the nuclear substance, distinct in structure from network and plasma, definitely limited and smoothed, always rounded in outline, usually suspended in the network, but often independent of it.' But when the minute structure and the relation of nucleoli to nuclear framework are inquired into, or the question of physiological rôle raised, very great diversity of opinion is found to obtain. (4) Bodies different in appearance from nucleoli may occur inside the nucleus, but of these little is known. (5) The wall which bounds the nucleus seems to be a true integral part of the latter, but disappears at the beginning of division.

(d) The Cell-wall.-In the older conception of the cell, which was practically that of a closed bag, the wall of the cell figured very prominently. But Nägeli showed (1845) that some vegetable cells were destitute of walls, Leydig (1857) defined the cell in respect to its substance, Schultze and others described naked Protozoa, and the progress of the 'protoplasmic movement' led to the abandonment of the position that the wall was a necessary or important part of the cell. In many cells, indeed, a limiting layer is very clearly present, and a sheath or cyst is especially characteristic of passive cells. Plant-cells are almost always distinguished by the possession of a limiting wall, of definite chemical composition, consisting of what is known as cellulose. An analogous wall occasionally occurs round animal cells. In the latter, however, the membrane is usually a comparatively slight thing, and may arise (1)

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from an aggregation of the threads and knots of the framework; (2) as a cuticle or capsule formed from the matrix or ground substance; (3) from a combination of both these elements. Leydig has shown that in a very wide series of animal cells the membrane, such as it is, is penetrated by small but definite pores. It is very important further to remember that both in plants and animals the cells are in a great number of cases connected with one another by intercellular bridges of protoplasm, and are in nowise to be thought of as closed bags. The cell-wall of plants, which, be it again noted, is a definite chemical substance, grows in extent and thickness by an intricate organic process, in the course of which new infinitesimal elements form apparently as intercalations between the old. The growth is in very many cases far from uniform; pits, ridges, and manifold kinds of sculpturing thus appear, and give rise to numerous detailed variations. The formation of new boundaries when a cell divides is a question of much difficulty; but in plant, and apparently in some animal cells, the formation of a cellular plate' is one of the last events in the dividing process.

III. Physiology of the Cell.-When the entire organism is simply a cell, as in most of the Protozoa and Protophyta, all the vital processes which in higher forms have their seat in special sets of cells, known as tissues and organs, are of course discharged by the unit-mass. Thus a unicellular organism like the Amoeba takes in energy as food in nutrition, works it up into living matter in digestion and assimilation, and expends it again in contraction and locomotion. As in any higher organism the oxygen required for the chemical breaking up of the protoplasmic molecules, the air for the vital flame, is taken in by the absorption known as respiration, and the waste carbonic acid gas is in an essentially similar way got rid of. Further, more solid ashes' of the vital combustion are formed in the Amoeba and in other actively living cells, and may pass out in excretion along with the refuse of unusable foodmaterial. The absence of a circulating fluid, of digestive glands, nerves, sense-organs, lungs, kidneys, and the like, does not in any way restrict the vital functions of a unicellular organism. All goes on as usual, only with greater chemical complexity, since all the different processes have but a unit-mass of protoplasm in which they occur. The physiology of independent cells, instead of being very simple, must be very complex, just because structure or differentiation is all but absent. It is, however, possible to express the manifold processes in a comparatively simple way by remembering what Claude Bernard was one of the first clearly to emphasise, that vital processes must be really only twofoldbuilding up and breaking down of living matter. On the one hand the protoplasm or real living matter is being by a series of chemical processes built up or constructed; on the other hand, in activity it is breaking down or being destroyed. The income of food or energy is, at the expense of the cellular organism, gradually raised into more and more complex and unstable compounds, until the genuine most complex and more unstable living matter itself is reached. On the opposite side, with liberation of energy in the form of work, this living matter breaks down into simpler and simpler compounds, until only the work, the waste products, and heat remain as the equivalent of the income of energy or food on the other side of the life-equation. On the one hand there are constructive processes, on the other, destructive; chemical synthesis and chemical dissolution is another expression of the contrast; while the two sets of processes are in more modern

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