est quantities, is most widely distributed throughout the visual apparatus, and is most easily set into function. Since assimilation and dissimilation are opposed processes, the principle of antagonism assumes great significance in Hering's theory: the principle is, indeed, its most characteristic feature. Its application to complementary colors-where the opposed processes in the several substances cancel each other- to contrast, to adaptation, to after-images, etc., follows naturally from the fundamental conception. Although the Hering theory is open to attack on various technical grounds, it undoubtedly covers the whole range of visual sensation more adequately than its rival. There is a good deal that is hypothetical in both theories. This is, however, a fault that recent work on the histology of the eye and on the function of the retinal elements is doing much to remedy. Within the last few years several new theories of visual sensation have come into the field. Most of them may, however, be regarded as modifications of one or other of the more classical theories just discussed. Their value and their relation to the older theories must be sought in the current literature of the subject. Visual Perception. It is characteristic of visual perception that all objects seen are spatial objects; that is, they occupy some place, some position in the spatial world; and they possess, likewise, spatial properties, form, distance, direction, etc. This characteristic, it should be noted, is shared by tactual perceptions; but it is not a mark of perception in general-not, for example, of the perceptions of melody, harmony, and rhythm. Since all visual perceptions are spatial, the chief problem they offer to psychology is the analysis of the spatial factors and the search for the conditions under which these factors operate. The simplest factor in visual space is extension. Every visual sensation comes to consciousness as an extended sensation. A color is always "spread out"; its parts lie side by side. In this respect, colors and brightnesses are essentially different from tones and noises, which lack the attribute of extension. Space, as it is perceived, is an orderly arrangement of extended objects. It never exists by itself alone. There is no such thing, in perception, as "mere" space or "empty" space. Only by abstraction are the spatial properties removed from objects; only by abstraction, as in mathematics, does empty space come into existence. Even such quasiabstract constructions as the line and the point do not properly figure in the psychology of space. It is, however, customary, within psychology, to distinguish two-dimensional and three-dimensional spaces; not because they differ fundamentally, but because they rest in part upon different conditions. The retina, being an extended organ upon which stimuli fall in patterns-thanks to the refractive functions of the transparent media forms a natural substrate for the perception of surface magnitudes. But the retina is not so well adapted for tridimensional perception -perception of solid objects. A special provision for depth-perception is made, however, in binocular vision; that is to say, in the difference of the two retinal images which are thrown upon the two eyes by a single object. This difference in binocular images depends upon the different Dositions from which the two eyes observe the object. Now it is conceivable that the two unlike images should have come to consciousness as two distinct objects. But, as a matter of fact, they do not, except under unusual circumstances-as when one squints or presses with the finger upon one eyeball. They do not even come to consciousness as two discrepant views of the same object. The difference in retinal images functions solely in the perception of depth or solidity. This is the principle involved in stereoscopic vision. Binocular perception of depth may be produced artificially by means of the stereoscope, an instrument which presents to the two eyes, under favorable conditions, two slightly different plane pictures of an object. Stereoscopic vision derives secondary aid, in ordinary perception, from linear and aerial perspective, from the known size of objects of reference, from change of position of the observer as well as of objects, from distribution of light and shade, etc. well upon ocular movements and the sensations The spatial functions of the eyes depend as which they arouse as upon the immediate retinal strated, by many lines of experimentation, that factors just considered. It has been demonwithout the possibility of movement (a condiwere the eyeballs set firmly within the head tion which is approximated in the case of certain fishes) visual perception of objects would be enormously handicapped. In the first place, movement allows the eye to travel over the object, exploring it from point to point; in the second place, it sets up sensations both in the external muscles that rotate the eye and in the internal muscles of accommodation; and finally. it is probable that to these factors must be added articular sensations from the rubbing of the eyes in their sockets. All these sensations, muscular, tendinous, and articular, play important roles in the determination of the spatial properties and relations of objects. The eyes, regarded as a perceiving organ, may be said, then, to fall into three parts; the retinas, which mediate visual sensations proper, and which function as a true double organ, the dioptric media, which focus the rays of light upon the retinas, and the movement-apparatus, which both alters the position of the retinal image and itself contributes kinæsthetic sensations from muscle, tendon, and orbit. Consult: Calkins, Introduction to Psychol ogy) (1901), ch. ii.; James, Principles of Psychology (1896), Vol. II., ch. xx.; Kuelpe, Outlines of Psychology) (1895), pp. 351-373; Stout, Manual of Psychology) (1899), pp. 141170; Wundt, Human and Animal Psychology': Titchener, Experimental Psychology, Vol. I. (1901), Part II., ch. i. For the structure and functions of the eye, consult also general textbooks of physiology. See EYE. VISION OF SIR LAUNFAL-VISITATION (nyctalopia) is a condition in which one sees better in a dim light than in a bright light, due to some opacity in the cornea, the crystalline lens, etc. It occurs in amblyopia (q.v.) and other affections which produce dimness of vision. Night-blindness (hemeralopia), on the other hand, is a state in which the person affected has normal vision in an ordinary light, but in twilight becomes suddenly blind. Double vision (diplopia) occurs when, as in some cases of squinting, each eye sees things separately. This defect arises from derangement of the visual axis, sometimes through muscular paralysis. In longsightedness or farsightedness (hyperopia or hypermetropia) objects are seen distinctly only at a range beyond that belonging to normal vision. Owing to the shortness of the eve-cavity the lenses are unable to converge the rays to a focus within the limits of the eyechamber, the image being therefore formed (theoretically) behind the eye. This defect is corrected by the use of convex lenses, which by converging the rays of light cause the image to fall on the retina. Shortsightedness or nearsightedness (myopia) is the reverse of longsightedness in causes as well as in effects. In this, owing to the too great power of the crystalline lens, or to the extension of the eye-cavity too far backward images from objects at some distance are formed in front of the retina, making the sight confused, if not entirely defective, for things beyond a certain limited range, while rendering it very clear for near objects. For remedying this condition biconcave glasses are employed, which, unless the myopia is serious, need be used only for looking at objects far off. Shortsightedness and longsightedness are usually congenital. Presbyopia is a defect similar to hyperopia, and usually comes on with advancing years, naturally beginning from the 40th to the 45th year It is due to diminished focusing power and lessened elasticity of the lens, the result of which is that the image of a near object is not clearly formed on the retina, but is formed behind it, while distant objects are seen as well as ever. Convex lenses are used for remedying this condition. Strabismus or squinting is a deformity often seen. and is ascribed to want of parallelism in the visual axes when the effort is made to direct both eyes to an object at the same time. It may be due to loss of power (paralysis) of one or more of the eye muscles; and this may depend on a merely local affection, or may be a symp tom of serious brain disease. But in the majority of instances and in all ordinary cases no such condition is present. The squint is said to be convergent when the squinting eye is directed toward the nose, and divergent when it is directed toward the temple; the convergent is much the more common. Concomitant strabismus is a variety of which the amount continues about the same in all positions of the fixationpoint When the direction of the eye or eyes is upward or downward the squinting is said to be vertical Convergent squint usually comes on during childhood, most often from the 2d to the 7th year. It is sometimes due to defective sight in the squinting eye, from congenital abnormality, severe inflammation, or injury; but very often no such condition is present. In a large proportion of cases it is accompanied by VOL. 2143 hypermetropia, and is due to the increased effort of accommodation required to see near objects, being associated with an increased and disproportionate effort of convergence. In such cases, if suitable glasses can be worn as soon as the squint begins to show itself, it may be prevented from becoming permanent. In other cases the presence of a squint may be traced to worms, the irritation of teething, etc.; and it disappears when the cause is removed. Divergent squint is very rarely present without considerable defect in the sight of the squinting eye, except where it is the result of over-correction of a convergent squint by operation. It is often associated with myopia, as the other form is with hypermetropia. The surgical operation for the correction of a squint consists in the division of the muscle whose excessive activity leads to the faulty position in convergent strabismus_the internal rectus, in divergent the external. It is often necessary to operate on both eyes in the same manner, even where the squint is monocular. In some cases it is requisite in addition to shorten the opposing muscle. See EYE; OPHTHALMIA; SENSES; VISION. Vision of Sir Launfal, län'fal, The, a poem by James Russell Lowell, founded on an Arthurian legend and published in 1845. Vision of Mirza, mèr'za, The, a famous allegory by Joseph Addison, which appeared in No. 159 of The Spectator.' Vision of Piers Plowman, pērz plow'man, The, an English poem of the 14th century, ascribed, chiefly on the ground of internal evidence, to William Langlande (q.v.) or Longland, a monk of Malvern, in spirit a Carlyle of the Middle Ages, crying out against abuses, insisting upon sincerity as the first of virtues. This poem belongs to the class of the dreampoem, and reflects both the England of the 14th century and the visionary, child-like medieval mind. Internal evidence fixes its date about 1362. Forty manuscript copies of it, belonging for the most part to the latter end of the 14th Three distinct century, attest its popularity. versions are extant, known as Texts A, B, and C. The probable date of Text A is 1362-3; of Text B, 1376-7; of Text C, 1398-9. The variations in these texts are considerable. An imitation of the poem, called 'Piers Plowman's Crede, appeared about 1393. The poet's vocabulary is similar to that of Chaucer, and several dialects are combined in it, the Midland dialect dominating. The metre is alliterative, long lines, divided into half-lines by a pause. Each line contains strong, or accented, syllables in fixed number, and weak or unaccented syllables in varying number. Consult Jusserand, Piers Plowman: a Contribution to the History of English Mysticism' (1893). Visita'tion, in an ecclesiastical sense, the visit of inspection by a bishop, archdeacon, elder or other authority to the churches within his jurisdiction. In the Protestant Episcopal churches the term is applied to an annual assembly of clergy and church-wardens, for the purpose of admitting church-wardens elect to office, reviewing the condition of the parish, answering inquiries relating thereto from the superior ecclesiastical authority, and receiving a charge from the bishop or his representative. Under the church establishment in England, the annual visitation is of an official as well as religiou character, and acts of Parliament bearing on church affairs are then formally communicated to the clergy and laity. Visitation Nuns. See ORDERS, RELIGIOUS. Visitation, Right of, the act of a naval commander who visits a ship of another nation to ascertain her character, and the object of her voyage. In time of war, a search is likely to follow if the replies to inquiries are not satisfactory. Visitation of the Sick (Ecclesiastical). This is an office of the Anglican Church for the comfort and consolation of sick persons. It is founded on the offices of ancient liturgies and, with some exceptions, is practically the same as Extreme Unction. Visitation of the Virgin Mary (Ecclesiastical). A festival celebrated on the second of July, to commemorate the visit of the Virgin to Elizabeth, the mother of John the Baptist, as described in Luke 1:39–56. Visiting Cards. It is probable that some form of evidence of a call on absent friends was used in very early times, perhaps originally among the Chinese or some other Oriental nation. It is somewhat uncertain when European custom first adopted the device, but it is generally stated that visiting cards were first used, in the western world, by the Germans in the sixteenth century. The court of Louis XIV, of France, the center of the fashion and etiquette of the seventeenth century, seized upon the custom as peculiarly apropos to the manners of the time, but added many an elaborate touch to the plain German taste in cards, in finish, execution and adornment. These, under Louis XV, engravings even of real or fanciful landscapes were added and, later, an autograph signature beneath the engraved picture. When England followed the lead of France in the use of visiting cards, in the eighteenth century, they came into use everywhere, with a return to their early simplicity; and, while they vary in size, shape and style of announcement, the modern tendency is decidedly in favor of simplicity and the avoidance of ostentation. Vis Major. A civil law term used to denote an inevitable accident, that is, one which could not have been avoided by the exercise of care because it is the result of the operation of the forces of nature., Visoko or Visoki. A town of Bosnia, on the river Bosna, fifteen miles northwest of Serajevo. It has a good trade in leather, tobacco and carpets. Pop. about 5000. Visscher, Cornelis. A Dutch engraver who lived about 1629-62. His portraits, the best known of which are "The Ratcatcher" and "Susanna at the Bath" are among the finest examples of Dutch engraving. In the last fifteen years of his life he produced about one hundred and fifty plates. Visscher, William Lightfoot, author; b. Owingsville, Ky., 25 Nov. 1842. He was educated at Bath Seminary, Owingsville, and in 1868 received the degree of LL.B. from the University of Louisville; he was admitted to the bar in 1868, but never practised law. He served as a soldier during the entire civil war. He has been engaged in newspaper work for many years, was a lecturer for several seasons, and later acted in dramas. He is the author of the following novels: (Carlisle of Colorado;) Way Out Yonder;) (Thou Art Peter;) (Ten Wise Men and Some More;) (Amos Hudsen's Motto.) His volumes of verse include (Black Mammy; Harp of the South;) Blue Grass Ballads; (Chicago, an Epic; and Poems of the South.) Vistula, vis'tu-la (German, Weichsel), a river of Central Europe, about 650 miles long, navigable from Cracow. It rises on the frontiers of Galicia and Austrian Silesia, on the northern declivity of the Carpathian Mountains, flows first eastward past the town of Cracow, forming from a point about 15 miles below Cracow, the boundary of Galicia and Poland, till it receives the San on the right bank, when it turns northwest through the Polish provinces, enters West Prussia a little above Thorn, and after traversing that province divides into two branches, of which the eastern, the Nogat, empties into the Frisches Haff; the western divides again about five miles from the Baltic into an eastern and a western branch, the latter, the Dantzic Vistula (which is much the larger), proceeding toward Dantzic, the former to the Frisches Haff. A new channel cut since 1895 from the head of the Dantzic branch now carries most of the water directly to the Baltic. The navigation of this river is important, especially to Poland, though often obstructed by ice or shallow water. The canal of Bromberg connects the Vistula, through the Netz and Warthe, with the Oder. Several navigable rivers empty into it. The area of its basin is about 76,000 square miles. Vita Nuova, vē'tä noo-ō'vä (It. (The New Life'), an early work by Dante, completed most probably in 1307. Vital Statistics. By this term is meant the statistical record of facts which pertain to life and death in any given community. The term is sufficiently comprehensive to include the records of the smallest kind of a village, or those of a nation, or even of all the nations of the world. Vital statistics may even be said to constitute a science, and such a science, indeed, as requires very considerable knowledge in mathematics and mnemonics to master it. It is well defined in the statement that it "comprises analysis and synthesis of facts concerning the life-history of populations." Its practical utility in the history of communities is very great, and is increasing every year. Any community which pretends to keep a record of its doings must have vital statistics, hence all civilized nations must have them. It not only enables a nation to know where it stands, but where it stands with reference to other nations. It informs those who seek such information as to the prevalence of disease and death, it suggests sanitary measures for the relief of unsanitary conditions, it encourages habits of careful observation and thoughtfulness on the part of those by whom statistics are provided, and it is the foundation of the census. Now the census includes not merely a count of the people every five or ten years, in a city, state, or nation, as anybody knows who has ever examined the bulky volumes of the census of the United States, but many other matters of great importance. Vital statistics when well prepared and accurate give valuable information, not only in regard to disease and death, but as to the VITAL STATISTICS number of the people and as to birth, age, sex, color, race, occupation, and conjugal relations. They are also the basis of data for life insurance calculations and they are concerned with the estimation of ratios in regard to births, marriages, and deaths and with the manipulation of figures for making a great many important deductions. It is essential that these fundamental statements should be accurate but unfortunately this is not always the case. There is therefore an element of possible error in vital statistics which must almost always be considered. They, however, usually permit conclusions which are approximately true, and by the aid of corrections they can be brought still nearer to the truth. The vital statistics of the United States are by no means complete for the entire country. Bulletin 109 published by the census bureau 1 Oct. 1911, and which gives the mortality record to Jan. 1911, declares that in only 21 of the States are the mortality statistics complete (at date), while in 16 other States they are given only for one or more of the large cities. This constitutes the so-called registration area of the United States. Other tables of vital statistics are equally incomplete and for some of the States they are wanting altogether. Much remains to be done, therefore, to place these data upon a basis which is as scientific and as accurate as the best records of the nations of Europe. It is to be hoped that this end will be attained in the census of 1920. The subject will be considered in this article under the divisions of population, birth, marriage, death, disease, and life tables. Population. This is the first fact which will be sought in preparing the vital statistics of any community. It is obtained by the census which is taken once in ten years by the nation, once in five years or oftener by some of the States and cities. It is inaccurate in various localities, sometimes from the dishonesty or incompetency of the enumerators and sometimes from the fault of those from whom information is sought. Revision of the last census in many of the cities and towns showed remarkable variations from the figures which had been obtained by the official gatherers. When the population of two or more places is known we have the first factor or element for making comparisons between these places. In the interval or intercensal years, when a direct count is not taken, an increase of population is usually presupposed, and is estimated by comparison of the two previous census enumerations. This is an inaccurate method, furthermore a decrease instead of an increase is often known to be the fact. Increase of population, for a given period, is due to the excess of births over deaths, as recorded in the archives of the board of health, or other office of registry, and to this must be added the excess of those who come into a community over those who leave it. Diminution of population is due to excess of deaths over births and to removals from the community. Population may increase slowly or rapidly and is greatly influenced by prosperity or the reverse, by sickness, by climatic conditions, or by the advantages or disadvantages of residence in the given community. Make-up of population refers to the relative numbers of males and females, and their ages. It also includes details as to color or race, and nationality. In many communities, especially in those which are large and highly organized, there is an excess of females over males. This is especially apt to be the case in manufacturing communities, while in pioneer settlements there is always an excess of males. In villages and small towns, especially in farming communities with their preponderance of out-door work, this is also the case. Age statistics are usually arranged according to decades, except that the infant population includes those who are under one year of age. Still-births, of course, make no addition to the population, but a record of them is important for it may lead to deductions which are of great significance for a given community. Age statistics have a very important relation to mortality statistics. The highest mortality rate is in infancy, and as this rate in some localities is extreme, it should call for study and investigation in such localities, especially when the total mortality rate unusually high." Color is an important detail in the records of population. There are many communities in which there is but one color, black, white, red, or yellow, but on the other hand the United States is a very composite nation, and hence there is a very positive necessity for the color distinction for a large portion of the population. The statement applies even to a greater degree in regard to nationality. As there may be 20 or more nationalities in a single city the necessity for classification is apparent enough. The sparse population in certain farming districts, especially in the less fertile or the newly settled portions of the country, or in those which are unfavorably located from sanitary or commercial conditions, the crowded population of the great cities where opportunities for labor are abundant, the overcrowding of the slums, and the abnormal housing of multitudes of human beings in many of the factory cities and villages furnish material for vital statistics which are invaluable from a sociological standpoint. They are also the basis of some of the most educating calculations with regard to mortality and morbidity rates. The rule was formerly accepted by statisticians as generally applicable that the greater the density of population the higher the death rate, but the many sanitary improvements in housing arrangements in recent years, especially in localities where the density of population is great, have considerably modified this rule. The mortality rate in such localities is now much lower than it was a few years ago, and this improvement applies not to the United States only but to the civilized world. Statistics in regard to population are taken periodically or intermittently, while those which relate to birth, death, marriage, and disease, which are sometimes called registrar's returns, are constantly in the process of making. Every community, large or small, has them as an essential portion of its records or archives. In the record of diseases, especially those which are of an infectious or contagious character, the list is increasing from year to year. It is easy to see that many valuable deductions and comparisons can be made from such records, especially in regard to sanitary and hygienic improvements. In all places of any considerable size they are now under the control of boards of health which are usually endowed by the legislatures with ample legal powers. In using statistics of this character it is not only desirable that they should be accurate but that they should be extended over as long a period of years as possible. This permits comparisons, the establishment of averages and the drawing of conclusions which would not otherwise be possible. In making comparisons it must be remembered that data should be of the same class or kind, for only such admit of comparison. Births. Making a record of births is a custom which is at least as old as civilization. it was a standing custom in the Roman empire at the foundation of the Christian era, to go back no further, and has been continued ever since by the town or parish clerk or notary, or by the clerk of the church. It is now one of the functions of the board of health, and physicians, midwives and others are authorized or compelled by law to report all births within a given time of their occurrence, usually within one or two days. These records are usually inaccurate because those who should report them are frequently careless and negligent about it, or the authorities are careless in enforcing the law. Many births which are unattended by physicians or midwives are never recorded. A proper penalty, but not one which is too severe, ought to be inflicted when this law is disobeyed. Bearing in mind the facts which have been mentioned, and remembering also that in some of the States there is no law requiring the registration of births, deaths, marriages and sickness, the statement concerning the imperfect character of our vital statistics, and their consequent want of value, will be found correct. Crude birth-rate is estimated at so many per thousand of the population. The birth rate must also be considered in preparing tables with reference to the number of women of childbearing age, and with reference to legitimacy and illegitimacy. Still births, as already stated, do not form an element in population, but they must be registered. They have been estimated at from 2.5 to 4 per cent of all births, and this estimate is probably too low. The birth rate of different countries or cities or States is often a matter of study and comparison. It is usually higher in the cities than in the country. The rate is higher when times are prosperous than when they are adverse, as economists noted a century ago. It is higher in manufacturing communities than in those which are residential, higher among the ignorant than among the intelligent. A high birth rate often, but not necessarily, means a high death rate, for the mortality in infancy, as already stated, is higher than at any other period of life, but a hh birth rate may also mean that the population is a vigorous one. A low birth rate may signify a low death rate but it may be followed by a high death rate. For a number of years the birth rate in most of the civilized countries of the world has been declining, and in view of the increasing cost of living in all of them it will probably continue to decline. It is declining in England, it is declining in the United States, while it has been declining in France for so many years that it causes persistent alarm to her government. Marriages. A record of marriages is equally as important as that of births, and the custom of keeping it is almost equally ancient. It is the bond of the family and one of the most important props of civilization. Both church and state have kept marriage records and continue to do so. It seems unnecessary that there should be a double record. In countries in which church and state are united, the church will insist upon its right to this record, and in those which are like our own, and in which church and state are separate, the right of the state to keep it should be insisted upon. It is so insisted upon wherever there are boards of health and a license or permission to marry must first be obtained from the local government, while the record of the marriage performance is preserved. Marriage rates, like birth rates, are estimated at so many per 1,000 of the population, the number of persons who are actually married being double the number of the marriages. A better record would include those who are of marriageable age. The marriage rate varies and fluctuates in accordance with certain conditions. It increases in times of commercial prosperity with abundance of labor, and in communities in which the occupations are healthful and productive of vigor and vitality. It diminishes during hard times, during war, and at times when the physical condition of those who are of marriageable age is lowered by disease, especially by epidemic disease or by disease which results from unhealthful occupations. In many communities there are more marriages during the summer than during the winter. An unusually high marriage rate may be followed by one which is correspondingly low, as when great business prosperity is followed by great business depression. This is simply the verification of a well settled economic law. It has been observed that more women than men marry several times during their lives. This must mean either that the inclination to marry repeatedly is more common in women than in men, or that women, more than men feel the need of a home and of other things which marriage is supposed to afford, or that marriageable women live longer than marriageable men. The age at which marriage is consummated is greater now than formerly. This is perhaps due to the increasing sense of the responsibilities which are connected with marriage, which is a hopeful indication, or it may be due, and often is due to inability to support a family in early life, in consequence of the increase in the cost of living, according to present standards. The fact that so many women are now working at gainful occupations, and that so many elect a career from their own efforts, in preference to the cares of a household, is an additional reason for the change in the marriage rate. The marriage age is an important factor in reference to population. Children who are born of mature parents are much more likely to be vigorous and healthy than those of the immature and the aged. The statistics of divorce are intimately associated with those of marriage. In a country like the United States, in which divorce prevails to such an alarming extent, it is especially desirable that the records should be made with the greatest care and accuracy. The spreading |