Etymology.

The word "vertebrate" derives from the Latin word "vertebratus" (Pliny), meaning "joint of the spine."  "Vertebrate" is derived from the word "vertebra", which refers to any of the bones or segments of the spinal column.

Anatomy and morphology.

All vertebrates are built along the basic chordate body plan: a stiff rod running through the length of the animal (vertebral column and/or notochord), with a hollow tube of nervous tissue (the spinal cord) above it and the gastrointestinal tract below.  In all vertebrates, the mouth is found at, or right below, the anterior end of the animal, while the anus opens to the exterior before the end of the body. The remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut.

Vertebral column.

The defining characteristic of a vertebrate is the vertebral column, in which the notochord (a stiff rod of uniform composition) found in all chordates has been replaced by a segmented series of stiffer elements (vertebrae) separated by mobile joints (intervertebral discs, derived embryonically and evolutionarily from the notochord).  However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon and coelacanth. Jawed vertebrates are typified by paired appendages (fins or legs, which may be secondarily lost), but this trait is not required in order for an animal to be a vertebrate.

Gills.

All basal vertebrates breathe with gills. The gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior. Each gill is supported by a cartilagenous or bony gill arch. The bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their chordate relatives have more than 50 pairs of gills.  In amphibians and some primitive bony fishes, the larvae bear external gills, branching off from the gill arches. These are reduced in adulthood, their function taken over by the gills proper in fishes and by lungs in most amphibians. Some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods.  While the more derived vertebrates lack gills, the gill arches form during fetal development, and form the basis of essential structures such as jaws, the thyroid gland, the larynx, the "columella" (corresponding to the stapes in mammals) and, in mammals, the malleus and incus.

Central nervous system.

The central nervous system of vertebrates is based on a hollow nerve cord running along the length of the animal. Of particular importance and unique to vertebrates is the presence of neural crest cells. These are progenitors of stem cells, and critical to coordinating the functions of cellular components. Neural crest cells migrate through the body from the nerve cord during development, and initiate the formation of neural ganglia and structures such as the jaws and skull.  The vertebrates are the only chordate group to exhibit cephalisation, the concentration of brain functions in the head. A slight swelling of the anterior end of the nerve cord is found in the lancelet, a chordate, though it lacks the eyes and other complex sense organs comparable to those of vertebrates. Other chordates do not show any trends towards cephalisation.  A peripheral nervous system branches out from the nerve cord to innervate the various systems. The front end of the nerve tube is expanded by a thickening of the walls and expansion of the central canal of spinal cord into three primary brain vesicles: The prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain), further differentiated in the various vertebrate groups. Two laterally placed eyes form around outgrowths from the midbrain, except in hagfish, though this may be a secondary loss. The forebrain is well-developed and subdivided in most tetrapods, while the midbrain dominates in many fish and some salamanders. Vesicles of the forebrain are usually paired, giving rise to hemispheres like the cerebral hemispheres in mammals.  The resulting anatomy of the central nervous system, with a single hollow nerve cord topped by a series of (often paired) vesicles, is unique to vertebrates. All invertebrates with well-developed brains, such as insects, spiders and squids, have a ventral rather than dorsal system of ganglions, with a split brain stem running on each side of the mouth or gut.

Evolutionary history.

First vertebrates.

Vertebrates originated about 525 million years ago during the Cambrian explosion, which saw rise in organism diversity. The earliest known vertebrate is believed to be the "Myllokunmingia". Another early vertebrate is "Haikouichthys ercaicunensis". Unlike the other fauna that dominated the Cambrian, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail. All of these early vertebrates lacked jaws in the common sense and relied on filter feeding close to the seabed. A vertebrate group of uncertain phylogeny, small eel-like conodonts, are known from microfossils of their paired tooth segments from the late Cambrian to the end of the Triassic.

From fish to amphibians.

The first jawed vertebrates may have appeared in the late Ordovician and became common in the Devonian, often known as the "Age of Fishes". The two groups of bony fishes, the actinopterygii and sarcopterygii, evolved and became common. The Devonian also saw the demise of virtually all jawless fishes save for lampreys and hagfish, as well as the Placodermi, a group of armoured fish that dominated the entirety of that period since the late Silurian. The Devonian also saw the rise of the first labyrinthodonts, which was a transitional form between fishes and amphibians.

Mesozoic vertebrates.

Amniotes branched from labyrinthodonts in the subsequent Carboniferous period. The Parareptilia and synapsid amniotes were common during the late Paleozoic, while diapsids became dominant during the Mesozoic. In the sea, the bony fishes became dominant. Birds, a derived form of dinosaur, evolved in the Jurassic. The demise of the non-avian dinosaurs at the end of the Cretaceous allowed for the expansion of mammals, which had evolved from the therapsids, a group of synapsid amniotes, during the late Triassic Period.

After the Mesozoic.

The Cenozoic world has seen great diversification of bony fishes, amphibians, reptiles, birds and mammals.  Over half of all living vertebrate species (about 32,000 species) are fish (non-tetrapod craniates), a diverse set of lineages that inhabit all the world's aquatic ecosystems, from snow minnows (Cypriniformes) in Himalayan lakes at elevations over to flatfishes (order Pleuronectiformes) in the Challenger Deep, the deepest ocean trench at about. Fishes of myriad varieties are the main predators in most of the world's water bodies, both freshwater and marine. The rest of the vertebrate species are tetrapods, a single lineage that includes amphibians (with roughly 7,000 species); mammals (with approximately 5,500 species); and reptiles and birds (with about 20,000 species divided evenly between the two classes). Tetrapods comprise the dominant megafauna of most terrestrial environments and also include many partially or fully aquatic groups (e.g., sea snakes, penguins, cetaceans).

Classification.

There are several ways of classifying animals. Evolutionary systematics relies on anatomy, physiology and evolutionary history, which is determined through similarities in anatomy and, if possible, the genetics of organisms. Phylogenetic classification is based solely on phylogeny. Evolutionary systematics gives an overview; phylogenetic systematics gives detail. The two systems are thus complementary rather than opposed.

Traditional classification.

Conventional classification has living vertebrates grouped into seven classes based on traditional interpretations of gross anatomical and physiological traits. This classification is the one most commonly encountered in school textbooks, overviews, non-specialist, and popular works. The extant vertebrates are:  In addition to these, there are two classes of extinct armoured fishes, the Placodermi and the Acanthodii.  Other ways of classifying the vertebrates have been devised, particularly with emphasis on the phylogeny of early amphibians and reptiles. An example based on Janvier (1981, 1997), Shu "et al." (2003), and Benton (2004) is given here:  †: Extinct  While this traditional classification is orderly, most of the groups are paraphyletic, i.e. do not contain all descendants of the class's common ancestor. For instance, descendants of the first reptiles include modern reptiles as well as mammals and birds; the agnathans have given rise to the jawed vertebrates; the bony fishes have given rise to the land vertebrates; the traditional "amphibians" have given rise to the reptiles (traditionally including the synapsids or mammal-like "reptiles"), which in turn have given rise to the mammals and birds. Most scientists working with vertebrates use a classification based purely on phylogeny, organized by their known evolutionary history and sometimes disregarding the conventional interpretations of their anatomy and physiology.

Phylogenetic relationships.

In phylogenetic taxonomy, the relationships between animals are not typically divided into ranks but illustrated as a nested "family tree" known as a phylogenetic tree. The one below is based on studies compiled by Philippe Janvier and others for the "Tree of Life Web Project" and Delsuc et al. † denotes an entirely extinct clade.

Number of extant species.

The number of described vertebrate species are split evenly between tetrapods and fish. The following table lists the number of described extant species for each vertebrate class as estimated in the IUCN Red List of Threatened Species, 2014.3. The IUCN estimates that 1,305,075 extant invertebrate species have been described, which means that less than 5% of the described animal species in the world are vertebrates.

Vertebrate species databases.

The following databases maintain (more or less) up-to-date lists of vertebrate species:

Reproductive systems.

Nearly all vertebrates undergo sexual reproduction. They produce haploid gametes by meiosis. The smaller, motile gametes are spermatozoa and the larger, non-motile gametes are ova. These fuse by the process of fertilisation to form diploid zygotes, which develop into new individuals.

Inbreeding.

During sexual reproduction, mating with a close relative (inbreeding) often leads to inbreeding depression. Inbreeding depression is considered to be largely due to expression of deleterious recessive mutations. The effects of inbreeding have been studied in many vertebrate species.  In several species of fish, inbreeding was found to decrease reproductive success.  Inbreeding was observed to increase juvenile mortality in 11 small animal species.  A common breeding practice for pet dogs is mating between close relatives (e.g. between half- and full siblings). This practice generally has a negative effect on measures of reproductive success, including decreased litter size and puppy survival.  Incestuous matings in birds result in severe fitness costs due to inbreeding depression (e.g. reduction in hatchability of eggs and reduced progeny survival).

Inbreeding avoidance.

As a result of the negative fitness consequences of inbreeding, vertebrate species have evolved mechanisms to avoid inbreeding.  Numerous inbreeding avoidance mechanisms operating prior to mating have been described. Toads and many other amphibians display breeding site fidelity. Individuals that return to natal ponds to breed will likely encounter siblings as potential mates. Although incest is possible, "Bufo americanus" siblings rarely mate. These toads likely recognize and actively avoid close kin as mates. Advertisement vocalizations by males appear to serve as cues by which females recognize their kin.  Inbreeding avoidance mechanisms can also operate subsequent to copulation. In guppies, a post-copulatory mechanism of inbreeding avoidance occurs based on competition between sperm of rival males for achieving fertilization. In competitions between sperm from an unrelated male and from a full sibling male, a significant bias in paternity towards the unrelated male was observed.  When female sand lizards mate with two or more males, sperm competition within the female's reproductive tract may occur. Active selection of sperm by females appears to occur in a manner that enhances female fitness. On the basis of this selective process, the sperm of males that are more distantly related to the female are preferentially used for fertilization, rather than the sperm of close relatives. This preference may enhance the fitness of progeny by reducing inbreeding depression.

Outcrossing.

Mating with unrelated or distantly related members of the same species is generally thought to provide the advantage of masking deleterious recessive mutations in progeny (see heterosis). Vertebrates have evolved numerous diverse mechanisms for avoiding close inbreeding and promoting outcrossing (see inbreeding avoidance).  Outcrossing as a way of avoiding inbreeding depression has been especially well studied in birds. For instance, inbreeding depression occurs in the great tit ("Parus major") when the offspring are produced as a result of a mating between close relatives. In natural populations of the great tit, inbreeding is avoided by dispersal of individuals from their birthplace, which reduces the chance of mating with a close relative.  Purple-crowned fairywren females paired with related males may undertake extra-pair matings that can reduce the negative effects of inbreeding, despite ecological and demographic constraints.  Southern pied babblers ("Turdoides bicolor") appear to avoid inbreeding in two ways: through dispersal and by avoiding familiar group members as mates. Although both males and females disperse locally, they move outside the range where genetically related individuals are likely to be encountered. Within their group, individuals only acquire breeding positions when the opposite-sex breeder is unrelated.  Cooperative breeding in birds typically occurs when offspring, usually males, delay dispersal from their natal group in order to remain with the family to help rear younger kin. Female offspring rarely stay at home, dispersing over distances that allow them to breed independently or to join unrelated groups.

Parthenogenesis.

Parthenogenesis is a natural form of reproduction in which growth and development of embryos occur without fertilization.  Reproduction in squamate reptiles is ordinarily sexual, with males having a ZZ pair of sex determining chromosomes, and females a ZW pair. However, various species, including the Colombian Rainbow boa ("Epicrates maurus"), "Agkistrodon contortrix" (copperhead snake) and "Agkistrodon piscivorus" (cotton mouth snake) can also reproduce by facultative parthenogenesis—that is, they are capable of switching from a sexual mode of reproduction to an asexual mode—resulting in production of WW female progeny. The WW females are likely produced by terminal automixis.  Mole salamanders are an ancient (2.4–3.8 million year-old) unisexual vertebrate lineage. In the polyploid unisexual mole salamander females, a premeiotic endomitotic event doubles the number of chromosomes. As a result, the mature eggs produced subsequent to the two meiotic divisions have the same ploidy as the somatic cells of the female salamander. Synapsis and recombination during meiotic prophase I in these unisexual females is thought to ordinarily occur between identical sister chromosomes and occasionally between homologous chromosomes. Thus little, if any, genetic variation is produced. Recombination between homeologous chromosomes occurs only rarely, if at all. Since production of genetic variation is weak, at best, it is unlikely to provide a benefit sufficient to account for the long-term maintenance of meiosis in these organisms.

Self-fertilization.

The mangrove killifish ("Kryptolebias marmoratus") produces both eggs and sperm by meiosis and routinely reproduces by self-fertilisation. This capacity has apparently persisted for at least several hundred thousand years. Each individual hermaphrodite normally fertilizes itself through uniting inside the fish's body of an egg and a sperm that it has produced by an internal organ. In nature, this mode of reproduction can yield highly homozygous lines composed of individuals so genetically uniform as to be, in effect, identical to one another. Although inbreeding, especially in the extreme form of self-fertilization, is ordinarily regarded as detrimental because it leads to expression of deleterious recessive alleles, self-fertilization does provide the benefit of "fertilization assurance" (reproductive assurance) at each generation.

Population trends.

The Living Planet Index, following 16,704 populations of 4,005 species of vertebrates, shows a decline of 60% between 1970 and 2014. Since 1970, freshwater species declined 83%, and tropical populations in South and Central America declined 89%. The authors note that, "An average trend in population change is not an average of total numbers of animals lost." According to WWF, this could lead to a sixth major extinction event. The five main causes of biodiversity loss are land-use change, overexploitation of natural resources, climate change, pollution and invasive species.

Vertebrates () comprise all species of animals within the subphylum Vertebrata () (chordates with backbones). Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. Vertebrates include such groups as the following:

脊椎动物亚门(学名:;拉丁文词根“vertebra”意为脊椎骨),是动物界脊索动物门下的一个亚门。目前所知最早的脊椎动物是中国云南省昆明发现的丰娇昆明鱼,距今约5.2亿年前。


Etymology and terminology.

The English word "breast" derives from the Old English word "brēost" (breast, bosom) from Proto-Germanic "breustam" (breast), from the Proto-Indo-European base bhreus– (to swell, to sprout). The "breast" spelling conforms to the Scottish and North English dialectal pronunciations. The "Merriam-Webster Dictionary" states that "Middle English brest, [comes] from Old English brēost; akin to Old High German brust..., Old Irish brú [belly], [and] Russian bryukho"; the first known usage of the term was before the 12th century.  A large number of colloquial terms for breasts are used in English, ranging from fairly polite terms to vulgar or slang. Some vulgar slang expressions may be considered to be derogatory or sexist to women.

Anatomy.

In women, the breasts overlie the pectoralis major muscles and usually extend from the level of the second rib to the level of the sixth rib in the front of the human rib cage; thus, the breasts cover much of the chest area and the chest walls. At the front of the chest, the breast tissue can extend from the clavicle (collarbone) to the middle of the sternum (breastbone). At the sides of the chest, the breast tissue can extend into the axilla (armpit), and can reach as far to the back as the latissimus dorsi muscle, extending from the lower back to the humerus bone (the bone of the upper arm). As a mammary gland, the breast is composed of differing layers of tissue, predominantly two types: adipose tissue; and glandular tissue, which affects the lactation functions of the breasts. Morphologically the breast is tear-shaped. The superficial tissue layer (superficial fascia) is separated from the skin by 0.5–2.5 cm of subcutaneous fat (adipose tissue). The suspensory Cooper's ligaments are fibrous-tissue prolongations that radiate from the superficial fascia to the skin envelope. The female adult breast contains 14–18 irregular lactiferous lobes that converge at the nipple. The 2.0–4.5 mm milk ducts are immediately surrounded with dense connective tissue that support the glands. Milk exits the breast through the nipple, which is surrounded by a pigmented area of skin called the areola. The size of the areola can vary widely among women. The areola contains modified sweat glands known as Montgomery's glands. These glands secrete oily fluid that lubricate and protect the nipple during breastfeeding. Volatile compounds in these secretions may also serve as an olfactory stimulus for the newborn's appetite.  The dimensions and weight of the breast vary widely among women. A small-to-medium-sized breast weighs 500 grams (1.1 pounds) or less, and a large breast can weigh approximately 750 to 1,000 grams (1.7 to 2.2 pounds) or more. The tissue composition ratios of the breast also vary among women. Some women's breasts have varying proportions of glandular tissue than of adipose or connective tissues. The fat-to-connective-tissue ratio determines the density or firmness of the breast. During a woman's life, her breasts change size, shape, and weight due to hormonal changes during puberty, the menstrual cycle, pregnancy, breastfeeding, and menopause.

Glandular structure.

The breast is an apocrine gland that produces the milk used to feed an infant. The nipple of the breast is surrounded by the areola (nipple-areola complex). The areola has many sebaceous glands, and the skin color varies from pink to dark brown. The basic units of the breast are the terminal duct lobular units (TDLUs), which produce the fatty breast milk. They give the breast its offspring-feeding functions as a mammary gland. They are distributed throughout the body of the breast. Approximately two-thirds of the lactiferous tissue is within 30 mm of the base of the nipple. The terminal lactiferous ducts drain the milk from TDLUs into 4–18 lactiferous ducts, which drain to the nipple. The milk-glands-to-fat ratio is 2:1 in a lactating woman, and 1:1 in a non-lactating woman. In addition to the milk glands, the breast is also composed of connective tissues (collagen, elastin), white fat, and the suspensory Cooper's ligaments. Sensation in the breast is provided by the peripheral nervous system innervation by means of the front (anterior) and side (lateral) cutaneous branches of the fourth-, fifth-, and sixth intercostal nerves. The T-4 nerve (Thoracic spinal nerve 4), which innervates the dermatomic area, supplies sensation to the nipple-areola complex.

Lymphatic drainage.

Approximately 75% of the lymph from the breast travels to the axillary lymph nodes on the same side of the body, whilst 25% of the lymph travels to the parasternal nodes (beside the sternum bone). A small amount of remaining lymph travels to the other breast and to the abdominal lymph nodes. The axillary lymph nodes include the pectoral (chest), subscapular (under the scapula), and humeral (humerus-bone area) lymph-node groups, which drain to the central axillary lymph nodes and to the apical axillary lymph nodes. The lymphatic drainage of the breasts is especially relevant to oncology because breast cancer is common to the mammary gland, and cancer cells can metastasize (break away) from a tumour and be dispersed to other parts of the body by means of the lymphatic system.

Shape, texture, and support.

The morphologic variations in the size, shape, volume, tissue density, pectoral locale, and spacing of the breasts determine their natural shape, appearance, and position on a woman's chest. Breast size and other characteristics do not predict the fat-to-milk-gland ratio or the potential for the woman to nurse an infant. The size and the shape of the breasts are influenced by normal-life hormonal changes (thelarche, menstruation, pregnancy, menopause) and medical conditions (e.g. virginal breast hypertrophy). The shape of the breasts is naturally determined by the support of the suspensory Cooper's ligaments, the underlying muscle and bone structures of the chest, and by the skin envelope. The suspensory ligaments sustain the breast from the clavicle (collarbone) and the clavico-pectoral fascia (collarbone and chest) by traversing and encompassing the fat and milk-gland tissues. The breast is positioned, affixed to, and supported upon the chest wall, while its shape is established and maintained by the skin envelope. In most women, one breast is slightly larger than the other. More obvious and persistent asymmetry in breast size occurs in up to 25% of women.  While it has been a common belief that breastfeeding causes breasts to sag, researchers have found that a woman's breasts sag due to four key factors: cigarette smoking, number of pregnancies, gravity, and weight loss or gain.  The base of each breast is attached to the chest by the deep fascia over the pectoralis major muscles. The space between the breast and the pectoralis major muscle, called retromammary space, gives mobility to the breast. The chest (thoracic cavity) progressively slopes outwards from the thoracic inlet (atop the breastbone) and above to the lowest ribs that support the breasts. The inframammary fold, where the lower portion of the breast meets the chest, is an anatomic feature created by the adherence of the breast skin and the underlying connective tissues of the chest; the IMF is the lower-most extent of the anatomic breast. Normal breast tissue typically has a texture that feels nodular or granular, to an extent that varies considerably from woman to woman. The study "The Evolution of the Human Breast" (2001) proposed that the rounded shape of a woman's breast evolved to prevent the sucking infant offspring from suffocating while feeding at the teat; that is, because of the human infant's small jaw, which did not project from the face to reach the nipple, he or she might block the nostrils against the mother's breast if it were of a flatter form (cf. common chimpanzee). Theoretically, as the human jaw receded into the face, the woman's body compensated with round breasts.

Development.

The breasts are principally composed of adipose, glandular, and connective tissues. Because these tissues have hormone receptors, their sizes and volumes fluctuate according to the hormonal changes particular to thelarche (sprouting of breasts), menstruation (egg production), pregnancy (reproduction), lactation (feeding of offspring), and menopause (end of menstruation).

Puberty.

The morphological structure of the human breast is identical in males and females until puberty. For pubescent girls in thelarche (the breast-development stage), the female sex hormones (principally estrogens) in conjunction with growth hormone promote the sprouting, growth, and development of the breasts. During this time, the mammary glands grow in size and volume and begin resting on the chest. These development stages of secondary sex characteristics (breasts, pubic hair, etc.) are illustrated in the five-stage Tanner Scale.  During thelarche the developing breasts are sometimes of unequal size, and usually the left breast is slightly larger. This condition of asymmetry is transitory and statistically normal in female physical and sexual development. Medical conditions can cause overdevelopment (e.g., virginal breast hypertrophy, macromastia) or underdevelopment (e.g., tuberous breast deformity, micromastia) in girls and women.  Approximately two years after the onset of puberty (a girl's first menstrual cycle), estrogen and growth hormone stimulate the development and growth of the glandular fat and suspensory tissues that compose the breast. This continues for approximately four years until the final shape of the breast (size, volume, density) is established at about the age of 21. Mammoplasia (breast enlargement) in girls begins at puberty, unlike all other primates in which breasts enlarge only during lactation.

Changes during the menstrual cycle.

During the menstrual cycle, the breasts are enlarged by premenstrual water retention and temporary growth.

Pregnancy and breastfeeding.

The breasts reach full maturity only when a woman's first pregnancy occurs. Changes to the breasts are among the very first signs of pregnancy. The breasts become larger, the nipple-areola complex becomes larger and darker, the Montgomery's glands enlarge, and veins sometimes become more visible. Breast tenderness during pregnancy is common, especially during the first trimester. By mid-pregnancy, the breast is physiologically capable of lactation and some women can express colostrum, a form of breast milk.  Pregnancy causes elevated levels of the hormone prolactin, which has a key role in the production of milk. However, milk production is blocked by the hormones progesterone and estrogen until after delivery, when progesterone and estrogen levels plummet.

Menopause.

At menopause, breast atrophy occurs. The breasts can decrease in size when the levels of circulating estrogen decline. The adipose tissue and milk glands also begin to wither. The breasts can also become enlarged from adverse side effects of combined oral contraceptive pills. The size of the breasts can also increase and decrease in response to weight fluctuations. Physical changes to the breasts are often recorded in the stretch marks of the skin envelope; they can serve as historical indicators of the increments and the decrements of the size and volume of a woman's breasts throughout the course of her life.

Breastfeeding.

The primary function of the breasts, as mammary glands, is the nourishing of an infant with breast milk. Milk is produced in milk-secreting cells in the alveoli. When the breasts are stimulated by the suckling of her baby, the mother's brain secretes oxytocin. High levels of oxytocin trigger the contraction of muscle cells surrounding the alveoli, causing milk to flow along the ducts that connect the alveoli to the nipple.  Full-term newborns have an instinct and a need to suck on a nipple, and breastfed babies nurse for both nutrition and for comfort. Breast milk provides all necessary nutrients for the first six months of life, and then remains an important source of nutrition, alongside solid foods, until at least one or two years of age.

Clinical significance.

The breast is susceptible to numerous benign and malignant conditions. The most frequent benign conditions are puerperal mastitis, fibrocystic breast changes and mastalgia.  Lactation unrelated to pregnancy is known as galactorrhea. It can be caused by certain drugs (such as antipsychotic medications), extreme physical stress, or endocrine disorders. Lactation in newborns is caused by hormones from the mother that crossed into the baby's bloodstream during pregnancy.

Breast cancer.

Breast cancer is the most common cause of cancer death among women and it is one of the leading causes of death among women. Factors that appear to be implicated in decreasing the risk of breast cancer are regular breast examinations by health care professionals, regular mammograms, self-examination of breasts, healthy diet, and exercise to decrease excess body fat, and breastfeeding.

Male breasts.

Both females and males develop breasts from the same embryological tissues. Normally, males produce lower levels of estrogens and higher levels of androgens, namely testosterone, which suppress the effects of estrogens in developing excessive breast tissue. In boys and men, abnormal breast development is manifested as gynecomastia, the consequence of a biochemical imbalance between the normal levels of estrogen and testosterone in the male body. Around 70% of boys temporarily develop breast tissue during adolescence. The condition usually resolves by itself within two years. When male lactation occurs, it is considered a symptom of a disorder of the pituitary gland.

Plastic surgery.

Plastic surgery can be performed to augment or reduce the size of breasts, or reconstruct the breast in cases of deformative disease, such as breast cancer. Breast augmentation and breast lift (mastopexy) procedures are done only for cosmetic reasons, whereas breast reduction is sometimes medically indicated. In cases where a woman's breasts are severely asymmetrical, surgery can be performed to either enlarge the smaller breast, reduce the size of the larger breast, or both.  Breast augmentation surgery generally does not interfere with future ability to breastfeed. Breast reduction surgery more frequently leads to decreased sensation in the nipple-areola complex, and to low milk supply in women who choose to breastfeed. Implants can interfere with mammography (breast x-rays images).

Society and culture.

General.

In Christian iconography, some works of art depict women with their breasts in their hands or on a platter, signifying that they died as a martyr by having their breasts severed; one example of this is Saint Agatha of Sicily.  Femen is a feminist activist group which uses topless protests as part of their campaigns against sex tourism religious institutions, sexism, homophobia and to "defend [women's] right to abortion". Femen activists have been regularly detained by police in response to their protests.  There is a long history of female breasts being used by comedians as a subject for comedy fodder (e.g., British comic Benny Hill's burlesque/slapstick routines).

Art history.

In European pre-historic societies, sculptures of female figures with pronounced or highly exaggerated breasts were common. A typical example is the so-called Venus of Willendorf, one of many Paleolithic Venus figurines with ample hips and bosom. Artifacts such as bowls, rock carvings and sacred statues with breasts have been recorded from 15,000 BC up to late antiquity all across Europe, North Africa and the Middle East.  Many female deities representing love and fertility were associated with breasts and breast milk. Figures of the Phoenician goddess Astarte were represented as pillars studded with breasts. Isis, an Egyptian goddess who represented, among many other things, ideal motherhood, was often portrayed as suckling pharaohs, thereby confirming their divine status as rulers. Even certain male deities representing regeneration and fertility were occasionally depicted with breast-like appendices, such as the river god Hapy who was considered to be responsible for the annual overflowing of the Nile.  Female breasts were also prominent in the Minoan civilization in the form of the famous Snake Goddess statuettes. In Ancient Greece there were several cults worshipping the "Kourotrophos", the suckling mother, represented by goddesses such as Gaia, Hera and Artemis. The worship of deities symbolized by the female breast in Greece became less common during the first millennium. The popular adoration of female goddesses decreased significantly during the rise of the Greek city states, a legacy which was passed on to the later Roman Empire.  During the middle of the first millennium BC, Greek culture experienced a gradual change in the perception of female breasts. Women in art were covered in clothing from the neck down, including female goddesses like Athena, the patron of Athens who represented heroic endeavor. There were exceptions: Aphrodite, the goddess of love, was more frequently portrayed fully nude, though in postures that were intended to portray shyness or modesty, a portrayal that has been compared to modern pin ups by historian Marilyn Yalom. Although nude men were depicted standing upright, most depictions of female nudity in Greek art occurred "usually with drapery near at hand and with a forward-bending, self-protecting posture". A popular legend at the time was of the Amazons, a tribe of fierce female warriors who socialized with men only for procreation and even removed one breast to become better warriors (the idea being that the right breast would interfere with the operation of a bow and arrow). The legend was a popular motif in art during Greek and Roman antiquity and served as an antithetical cautionary tale.

Body image.

Many women regard their breasts as important to their sexual attractiveness, as a sign of femininity that is important to their sense of self. A woman with smaller breasts may regard her breasts as less attractive.

Clothing.

Because breasts are mostly fatty tissue, their shape can—within limits—be molded by clothing, such as foundation garments. Bras are commonly worn by about 90% of Western women, and are often worn for support. The social norm in most Western cultures is to cover breasts in public, though the extent of coverage varies depending on the social context. Some religions ascribe a special status to the female breast, either in formal teachings or through symbolism. Islam forbids women from exposing their breasts in public.  Many cultures, including Western cultures in North America, associate breasts with sexuality and tend to regard bare breasts as immodest or indecent. In some cultures, like the Himba in northern Namibia, bare-breasted women are normal. In some African cultures, for example, the thigh is regarded as highly sexualised and never exposed in public, but breast exposure is not taboo. In a few Western countries and regions female toplessness at a beach is acceptable, although it may not be acceptable in the town center.  Social attitudes and laws regarding breastfeeding in public vary widely. In many countries, breastfeeding in public is common, legally protected, and generally not regarded as an issue. However, even though the practice may be legal or socially accepted, some mothers may nevertheless be reluctant to expose a breast in public to breastfeed due to actual or potential objections by other people, negative comments, or harassment. It is estimated that around 63% of mothers across the world have publicly breast-fed. Bare-breasted women are legal and culturally acceptable at public beaches in Australia and much of Europe. Filmmaker Lina Esco made a film entitled "Free the Nipple", which is about "...laws against female toplessness or restrictions on images of female, but not male, nipples", which Esco states is an example of sexism in society.

Sexual characteristic.

In some cultures, breasts play a role in human sexual activity. In Western culture, breasts have a "...hallowed sexual status, arguably more fetishized than either sex’s genitalia". Breasts and especially the nipples are among the various human erogenous zones. They are sensitive to the touch as they have many nerve endings; and it is common to press or massage them with hands or orally before or during sexual activity. During sexual arousal, breast size increases, venous patterns across the breasts become more visible, and nipples harden. Compared to other primates, human breasts are proportionately large throughout adult females' lives. Some writers have suggested that they may have evolved as a visual signal of sexual maturity and fertility.  Many people regard bare female breasts to be aesthetically pleasing or erotic, and they can elicit heightened sexual desires in men in many cultures. In the ancient Indian work the "Kama Sutra", light scratching of the breasts with nails and biting with teeth are considered erotic. Some people show a sexual interest in female breasts distinct from that of the person, which may be regarded as a breast fetish. A number of Western fashions include clothing which accentuate the breasts, such as the use of push-up bras and decollete (plunging neckline) gowns and blouses which show cleavage. While U.S. culture prefers breasts that are youthful and upright, some cultures venerate women with drooping breasts, indicating mothering and the wisdom of experience.  Research conducted at the Victoria University of Wellington showed that breasts are often the first thing men look at, and for a longer time than other body parts. The writers of the study had initially speculated that the reason for this is due to endocrinology with larger breasts indicating higher levels of estrogen and a sign of greater fertility, but the researchers said that "Men may be looking more often at the breasts because they are simply aesthetically pleasing, regardless of the size."  Some women report achieving an orgasm from nipple stimulation, but this is rare. Research suggests that the orgasms are genital orgasms, and may also be directly linked to "the genital area of the brain". In these cases, it seems that sensation from the nipples travels to the same part of the brain as sensations from the vagina, clitoris and cervix. Nipple stimulation may trigger uterine contractions, which then produce a sensation in the genital area of the brain.

Anthropomorphic geography.

There are many mountains named after the breast because they resemble it in appearance and so are objects of religious and ancestral veneration as a fertility symbol and of well-being. In Asia, there was "Breast Mountain", which had a cave where the Buddhist monk Bodhidharma (Da Mo) spent much time in meditation. Other such breast mountains are Mount Elgon on the Uganda-Kenya border, Beinn Chìochan and the Maiden Paps in Scotland, the "Bundok ng Susong Dalaga" (Maiden's breast mountains) in Talim Island, Philippines, the twin hills known as the Paps of Anu ("Dá Chích Anann" or "the breasts of Anu"), near Killarney in Ireland, the 2,086 m high "Tetica de Bacares" or "La Tetica" in the Sierra de Los Filabres, Spain, and Khao Nom Sao in Thailand, Cerro Las Tetas in Puerto Rico and the Breasts of Aphrodite in Mykonos, among many others. In the United States, the Teton Range is named after the French word for "breast".

The breast is one of two prominences located on the upper ventral region of the torso of primates. In females, it serves as the mammary gland, which produces and secretes milk to feed infants. Both females and males develop breasts from the same embryological tissues. At puberty, estrogens, in conjunction with growth hormone, cause breast development in female humans and to a much lesser extent in other primates. Breast development in other primate females generally only occurs with pregnancy.

乳房()位处于哺乳动物的胸部或腹部,左右成对出现。雌性的乳房包含乳腺等腺体,可分泌乳汁哺育幼儿。男性乳房一般不发育,但存有乳腺组织。


History of use.

Though most sources will say it was invented by Austrian composer Arnold Schoenberg in 1921 and first described privately to his associates in 1923, in fact Josef Matthias Hauer published his "law of the twelve tones" in 1919, and should be credited with inventing the technique, requiring that all twelve chromatic notes sound before any note is repeated. The method was used during the next twenty years almost exclusively by the composers of the Second Viennese School—Alban Berg, Anton Webern, and Schoenberg himself.  The twelve tone technique was preceded by "freely" atonal pieces of 1908–1923 which, though "free", often have as an "integrative element... a minute intervallic cell" which in addition to expansion may be transformed as with a tone row, and in which individual notes may "function as pivotal elements, to permit overlapping statements of a basic cell or the linking of two or more basic cells". The twelve-tone technique was also preceded by "nondodecaphonic serial composition" used independently in the works of Alexander Scriabin, Igor Stravinsky, Béla Bartók, Carl Ruggles, and others. Oliver Neighbour argues that Bartók was "the first composer to use a group of twelve notes consciously for a structural purpose", in 1908 with the third of his fourteen bagatelles. "Essentially, Schoenberg and Hauer systematized and defined for their own dodecaphonic purposes a pervasive technical feature of'modern' musical practice, the ostinato". Additionally, John Covach argues that the strict distinction between the two, emphasized by authors including Perle, is overemphasized:  The distinction often made between Hauer and the Schoenberg school—that the former's music is based on unordered hexachords while the latter's is based on an ordered series—is false: while he did write pieces that could be thought of as "trope pieces", much of Hauer's twelve-tone music employs an ordered series.  The "strict ordering" of the Second Viennese school, on the other hand, "was inevitably tempered by practical considerations: they worked on the basis of an interaction between ordered and unordered pitch collections."  Rudolph Reti, an early proponent, says: "To replace one structural force (tonality) by another (increased thematic oneness) is indeed the fundamental idea behind the twelve-tone technique," arguing it arose out of Schoenberg's frustrations with free atonality, providing a "positive premise" for atonality. In Hauer's breakthrough piece "Nomos", Op. 19 (1919) he used twelve-tone sections to mark out large formal divisions, such as with the opening five statements of the same twelve-tone series, stated in groups of five notes making twelve five-note phrases.  Schoenberg's idea in developing the technique was for it to "replace those structural differentiations provided formerly by tonal harmonies". As such, twelve-tone music is usually atonal, and treats each of the 12 semitones of the chromatic scale with equal importance, as opposed to earlier classical music which had treated some notes as more important than others (particularly the tonic and the dominant note).  The technique became widely used by the fifties, taken up by composers such as Milton Babbitt, Luciano Berio, Pierre Boulez, Luigi Dallapiccola, Ernst Krenek, Riccardo Malipiero, and, after Schoenberg's death, Igor Stravinsky. Some of these composers extended the technique to control aspects other than the pitches of notes (such as duration, method of attack and so on), thus producing serial music. Some even subjected all elements of music to the serial process.  Charles Wuorinen claimed in a 1962 interview that while "most of the Europeans say that they have 'gone beyond' and 'exhausted' the twelve-tone system", in America, "the twelve-tone system has been carefully studied and generalized into an edifice more impressive than any hitherto known."  American composer Scott Bradley, best known for his musical scores for work like "Tom & Jerry" and "Droopy Dog", utilized the 12-tone technique in his work. Bradley had learned the concept as a student of Schoenberg. Bradley described his use thus: An example of Bradley's use of the technique to convey building tension occurs in the "Tom & Jerry" short "Puttin' on the Dog", from 1953. In a scene where the mouse, wearing a dog mask, runs across a yard of dogs "in disguise", a chromatic scale represents both the mouse's movements, and the approach of a suspicious dog, mirrored octaves lower. Apart from his work in cartoon scores, Bradley also composed tone poems that were performed in concert in California.  Theodore Norman played the guitar part in Columbia Records' 1957 recordings of Schoenberg's Serenade, Opus 24 and Pierre Boulez's "Le Marteau sans maître" (The Hammer Without a Master). He went on to compose a number of twelve-tone pieces for solo guitar.

Tone row.

The basis of the twelve-tone technique is the "tone row", an ordered arrangement of the twelve notes of the chromatic scale (the twelve equal tempered pitch classes). There are four postulates or preconditions to the technique which apply to the row (also called a "set" or "series"), on which a work or section is based:  A particular transformation (prime, inversion, retrograde, retrograde-inversion) together with a choice of transpositional level is referred to as a "set form" or "row form". Every row thus has up to 48 different row forms. (Some rows have fewer due to symmetry; see the sections on "derived rows" and "invariance" below.)

Example.

Suppose the prime form of the row is as follows:  Then the retrograde is the prime form in reverse order:  The inversion is the prime form with the intervals inverted (so that a rising minor third becomes a falling minor third, or equivalently, a rising major sixth):  And the retrograde inversion is the inverted row in retrograde:  P, R, I and RI can each be started on any of the twelve notes of the chromatic scale, meaning that 47 permutations of the initial tone row can be used, giving a maximum of 48 possible tone rows. However, not all prime series will yield so many variations because transposed transformations may be identical to each other. This is known as "invariance". A simple case is the ascending chromatic scale, the retrograde inversion of which is identical to the prime form, and the retrograde of which is identical to the inversion (thus, only 24 forms of this tone row are available).  In the above example, as is typical, the retrograde inversion contains three points where the sequence of two pitches are identical to the prime row. Thus the generative power of even the most basic transformations is both unpredictable and inevitable. Motivic development can be driven by such internal consistency.

Application in composition.

Note that rules 1–4 above apply to the construction of the row itself, and not to the interpretation of the row in the composition. (Thus, for example, postulate 2 does not mean, contrary to common belief, that no note in a twelve-tone work can be repeated until all twelve have been sounded.) While a row may be expressed literally on the surface as thematic material, it need not be, and may instead govern the pitch structure of the work in more abstract ways. Even when the technique is applied in the most literal manner, with a piece consisting of a sequence of statements of row forms, these statements may appear consecutively, simultaneously, or may overlap, giving rise to harmony.  Needless to say, durations, dynamics and other aspects of music other than the pitch can be freely chosen by the composer, and there are also no general rules about which tone rows should be used at which time (beyond their all being derived from the prime series, as already explained). However, individual composers have constructed more detailed systems in which matters such as these are also governed by systematic rules (see serialism).

Properties of transformations.

The tone row chosen as the basis of the piece is called the "prime series" (P). Untransposed, it is notated as P. Given the twelve pitch classes of the chromatic scale, there are 12 factorial (479,001,600) tone rows, although this is far higher than the number of "unique" tone rows (after taking transformations into account). There are 9,985,920 classes of twelve-tone rows up to equivalence (where two rows are equivalent if one is a transformation of the other).  Appearances of P can be transformed from the original in three basic ways:  The various transformations can be combined. These give rise to a set-complex of forty-eight forms of the set, 12 transpositions of the "four" basic forms: P, R, I, RI. The combination of the retrograde and inversion transformations is known as the "retrograde inversion" ("RI").  thus, each cell in the following table lists the result of the transformations, a four-group, in its row and column headers:  However, there are only a few numbers by which one may "multiply" a row and still end up with twelve tones. (Multiplication is in any case not interval-preserving.)

Derivation.

"Derivation" is transforming segments of the full chromatic, fewer than 12 pitch classes, to yield a complete set, most commonly using trichords, tetrachords, and hexachords. A derived set can be generated by choosing appropriate transformations of any trichord except 0,3,6, the diminished triad. A derived set can also be generated from any tetrachord that excludes the interval class 4, a major third, between any two elements. The opposite, "partitioning", uses methods to create segments from sets, most often through registral difference.

Combinatoriality.

Combinatoriality is a side-effect of derived rows where combining different segments or sets such that the pitch class content of the result fulfills certain criteria, usually the combination of hexachords which complete the full chromatic.

Invariance.

"Invariant" formations are also the side effect of derived rows where a segment of a set remains similar or the same under transformation. These may be used as "pivots" between set forms, sometimes used by Anton Webern and Arnold Schoenberg.  "Invariance" is defined as the "properties of a set that are preserved under [any given] operation, as well as those relationships between a set and the so-operationally transformed set that inhere in the operation", a definition very close to that of mathematical invariance. George Perle describes their use as "pivots" or non-tonal ways of emphasizing certain pitches. Invariant rows are also combinatorial and derived.

Cross partition.

A "cross partition" is an often monophonic or homophonic technique which, "arranges the pitch classes of an aggregate (or a row) into a rectangular design", in which the vertical columns (harmonies) of the rectangle are derived from the adjacent segments of the row and the horizontal columns (melodies) are not (and thus may contain non-adjacencies).  For example, the layout of all possible 'even' cross partitions is as follows:  One possible realization out of many for the "order numbers" of the 3 cross partition, and one variation of that, are:  Thus if one's tone row was 0 e 7 4 2 9 3 8 t 1 5 6, one's cross partitions from above would be:  Cross partitions are used in Schoenberg's Op. 33a "Klavierstück" and also by Berg but Dallapicolla used them more than any other composer.

Other.

In practice, the "rules" of twelve-tone technique have been bent and broken many times, not least by Schoenberg himself. For instance, in some pieces two or more tone rows may be heard progressing at once, or there may be parts of a composition which are written freely, without recourse to the twelve-tone technique at all. Offshoots or variations may produce music in which:  Also, some composers, including Stravinsky, have used cyclic permutation, or rotation, where the row is taken in order but using a different starting note. Stravinsky also preferred the inverse-retrograde, rather than the retrograde-inverse, treating the former as the compositionally predominant, "untransposed" form.  Although usually atonal, twelve tone music need not be—several pieces by Berg, for instance, have tonal elements.  One of the best known twelve-note compositions is "Variations for Orchestra" by Arnold Schoenberg. "Quiet", in Leonard Bernstein's "Candide", satirizes the method by using it for a song about boredom, and Benjamin Britten used a twelve-tone row—a "tema seriale con fuga"—in his "Cantata Academica: Carmen Basiliense" (1959) as an emblem of academicism.

Schoenberg's mature practice.

Ten features of Schoenberg's mature twelve-tone practice are characteristic, interdependent, and interactive:

The twelve-tone technique—also known as dodecaphony, twelve-tone serialism, and (in British usage) twelve-note composition—is a method of musical composition first devised by Austrian composer Josef Matthias Hauer, who published his "law of the twelve tones" in 1919. In 1923, Arnold Schoenberg (1874–1951) developed his own, better-known version of 12-tone technique, which became associated with the "Second Viennese School" composers, who were the primary users of the technique in the first decades of its existence. The technique is a means of ensuring that all 12 notes of the chromatic scale are sounded as often as one another in a piece of music while preventing the emphasis of any one note through the use of tone rows, orderings of the 12 pitch classes. All 12 notes are thus given more or less equal importance, and the music avoids being in a key. Over time, the technique increased greatly in popularity and eventually became widely influential on 20th-century composers. Many important composers who had originally not subscribed to or actively opposed the technique, such as Aaron Copland and Igor Stravinsky, eventually adopted it in their music.

十二音技法()是20世纪古典音乐的一种创作手法。最先由奥地利作曲家约瑟夫·马蒂亚斯·豪尔和阿诺·荀白克分别提出。两者部分的概念类近,但并不互相从属,其中勋伯格的理论得到较多人认同,并在他所属的第二维也纳乐派间广泛流传。时至今日,十二音技法大都以勋伯格的理论为基础。


Kinds.

Three groups of Cyclopes can be distinguished: the Hesiodic, the Homeric and the wall-builders. In Hesiod's "Theogony", the Cyclopes are the three brothers: Brontes, Steropes, and Arges, sons of Uranus and Gaia, who made for Zeus his characteristic weapon, the thunderbolt. In Homer's "Odyssey", the Cyclopes are a uncivilized group of shepherds, one of whom, Polyphemus, the son of Poseidon, is encountered by Odysseus. Cyclopes were also said to have been the builders of the Cyclopean walls of Mycenae and Tiryns. A scholiast, quoting the fifth-century BC historian Hellanicus, tells us that, in addition to the Hesiodic Cyclopes (whom the scholiast describes as "the gods themselves"), and the Homeric Cyclopes, there was a third group of Cyclopes: the builders of the walls of Mycenae.

Hesiodic Cyclopes.

Hesiod, in the "Theogony" (c. 700 BC), described three Cyclopes: Brontes, Steropes, and Arges, who were the sons of Uranus (Sky) and Gaia (Earth), and the brothers of the Titans and Hundred-Handers, and who had a single eye set in the middle of their foreheads. They made for Zeus his all-powerful thunderbolt, and in so doing, the Cyclopes played a key role in the Greek succession myth, which told how the Titan Cronus overthrew his father Uranus, and how in turn Zeus overthrew Cronus and his fellow Titans, and how Zeus was eventually established as the final and permanent ruler of the cosmos. The names that Hesiod gives them: Arges (Bright), Brontes (Thunder), and Steropes (Lightning), reflect their fundamental role as thunderbolt makers. As early as the late seventh-century BC, the Cyclopes could be used by the Spartan poet Tyrtaeus to epitomize extraodinary size and strength.  According to the accounts of Hesiod and mythographer Apollodorus, the Cyclopes had been imprisoned by their father Uranus. Zeus later freed the Cyclopes, and they repaid him by giving him the thunderbolt. The Cyclopes provided for Hesiod, and others theogony-writers, a convenient source of heavenly weaponry, since the smith-god Hephaestus—who would eventually take over that role—had not yet been born. According to Apollodorus, the Cyclopes also provided Poseidon with his trident and Hades with his cap of invisibility, and the gods used these weapons to defeat the Titans.  Although the primordial Cyclopes of the "Theogony" were presumably immortal (as were their brothers the Titans), the sixth-century BC Hesiodic "Catalogue of Women", has them being killed by Apollo. Later sources tell us why: Apollo's son Asclepius had been killed by Zeus' thunderbolt, and Apollo killed the Cyclopes, the makers of the thunderbolt, in revenge. According to a scholiast on Euripides' "Alcestis", the fifth-century BC mythographer Pherecydes supplied the same motive, but said that Apollo, rather than killing the Cyclopes, killed their "sons" (one of whom he named Aortes) instead. No other source mentions any offspring of the Cyclopes. A Pindar fragment suggests that Zeus himself killed the Cyclopes to prevent them from making thunderbolts for anyone else.  The Cyclopes' prowess as craftsmen is stressed by Hesiod who says "strength and force and contrivances were in their works." Being such skilled craftsmen of great size and strength, later poets, beginning with the third-century BC poet Callimachus, imagine these Cyclopes, the primordial makers of Zeus' thunderbolt, becoming the assistants of the smith-god Hephaestus, at his forge in Sicily, underneath Mount Etna, or perhaps the nearby Aeolian Islands. In his "Hymn to Artemis", Callimachus has the Cyclopes on the Aeolian island of Lipari, working "at the anvils of Hephaestus", make the bows and arrows used by Apollo and Artemis. The first-century BC Latin poet Virgil, in his epic "Aeneid", has the Cyclopes: "Brontes and Steropes and bare-limbed Pyracmon" toil under the direction of Vulcan (Hephaestus), in caves underneath Mount Etna and the Aeolian islands. Virgil describes the Cyclopes, in Vulcan's smithy forging iron, making a thunderbolt, a chariot for Mars, and Pallas's Aegis, with Vulcan interrupting their work to command the Cyclopes to fashion arms for Aeneas. The later Latin poet Ovid also has the Hesiodic Cyclopes Brontes and Steropes (along with a third Cyclops named Acmonides), work at forges in Sicilian caves.  According to a Hellenistic astral myth, the Cyclopes were the builders of the first altar. The myth was a catasterism, which explained how the constellation the Altar (Ara) came to be in the heavens. According to the myth, the Cyclopes built an altar upon which Zeus and the other gods swore alliance before their war with the Titans. After their victory, "the gods placed the altar in the sky in commemoration", and thus began the practice, according to the myth, of men swearing oaths upon altars "as a guarantee of their good faith".  According to the second-century geographer Pausanias, there was a sanctuary called the "altar of the Cyclopes" on the Isthmus of Corinth at a place sacred to Poseidon, where sacrifices were offered to the Cyclopes. There is no evidence for any other cult associated with the Cyclopes. According to a version of the story in the "Iliad" scholia (found nowhere else), when Zeus swallowed Metis, she was pregnant with Athena by the Cyclops Brontes.  Although described by Hesiod as having "very violent hearts" ("ὑπέρβιον ἦτορ ἔχοντας"), and while their extraordinary size and strength would have made them capable of great violence, there is no indication of the Hesiodic Cyclopes having behaved in any other way than as dutiful servants of the gods.  Walter Burkert suggests that groups or societies of lesser gods, like the Hesiodic Cyclopes, "mirror real cult associations ("thiasoi")... It may be surmised that smith guilds lie behind Cabeiri, Idaian Dactyloi, Telchines, and Cyclopes."

Homeric Cyclopes.

In an episode of Homer's "Odyssey" (c. 700 BC), the hero Odysseus encounters the Cyclops Polyphemus, the son of Poseidon, a one-eyed man-eating giant who lives with his fellow Cyclopes in a distant land. The relationship between these Cyclopes and Hesiod's Cyclopes is unclear. Homer described a very different group of Cyclopes, than the skilled and subservient craftsman of Hesiod. Homer's Cyclopes live in the "world of men" rather than among the gods, as they presumably do in the "Theogony". The Homeric Cyclopes are presented as uncivilized shepherds, who live in caves, savages with no regard for Zeus. They have no knowledge of agriculture, ships or craft. They live apart and lack any laws.  The fifth-century BC playwright Euripides also told the story of Odysseus' encounter with Polyphemus in his satyr play "Cyclops". Euripides' Cyclopes, like Homer's, are uncultured cave-dwelling shepherds. They have no agriculture, no wine, and live on milk, cheese and the meat of sheep. They live solitary lives, and have no government. They are inhospitable to strangers, slaughtering and eating all who come to their land. While Homer does not say if the other Cyclopes are like Polyphemus in their appearance and parentage, Euripides' makes it explicit, calling the Cyclopes "Poseidon's one-eyed sons". And while Homer is vague as to their location, Euripides locates the land of the Cyclopes on the island of Sicily near Mount Etna.  Like Euripides, Virgil has the Cyclopes of Polyphemus live on Sicily near Etna. For Virgil apparently, these Homeric Cyclopes are members of the same race of Cyclopes as Hesiod's Brontes and Steropes, who live nearby.

Cyclopean wall-builders.

Cyclopes were also said to have been the builders of the so-called 'Cyclopean' walls of Mycenae, Tiryns, and Argos. Although they can be seen as being distinct, the Cyclopean wall-builders share several features with the Hesiodic Cyclopes: both groups are craftsmen of supernatural skill, possessing enormous strength, who lived in primordial times. These builder Cyclopes were apparently used to explain the construction of the stupendous walls at Mycenae and Tiryns, composed of massive stones that seemed too large and heavy to have been moved by ordinary men.  These master builders were famous in antiquity from at least the fifth century BC onwards. The poet Pindar, has Heracles driving the cattle of Geryon through the "Cyclopean portal" of the Tirynian king Eurystheus. The mythographer Pherecydes says that Perseus brought the Cyclopes with him from Seriphos to Argos, presumably to build the walls of Mycenae. Proetus, the mythical king of ancient Argos, was said to have brought a group of seven Cyclopes from Lycia to build the walls of Tiryns.  The late fifth and early fourth-century BC comic poet Nicophon wrote a play called either "Cheirogastores" or "Encheirogastores" ("Hands-to-Mouth"), which is thought to have been about these Cyclopean wall-builders. Ancient lexicographers explained the title as meaning "those who feed themselves by manual labour", and, according to Eustathius of Thessalonica, the word was used to describe the Cyclopean wall-builders, while "hands-to-mouth" was one of the three kinds of Cyclopes distinguished by scholia to Aelius Aristides. Similarly, possibly deriving from Nicophon's comedy, the first-century Greek geographer Strabo says these Cyclopes were called "Bellyhands" ("gasterocheiras") because they earned their food by working with their hands.  The first-century natural philosopher Pliny the Elder, in his "Natural History", reported a tradition, attributed to Aristotle, that the Cyclopes were the inventors of masonry towers. In the same work Pliny also mentions the Cyclopes, as being among those credited with being the first to work with iron, as well as bronze. In addition to walls, other monuments were attributed to the Cyclopes. For example, Pausanias says that at Argos there was "a head of Medusa made of stone, which is said to be another of the works of the Cyclopes".

Principal sources.

Hesiod.

According to the "Theogony" of Hesiod, Uranus (Sky) mated with Gaia (Earth) and produced eighteen children. First came the twelve Titans, next came the three one-eyed Cyclopes:  Following the Cyclopes, Gaia next gave birth to three more monstrous brothers, the Hecatoncheires, or Hundred-Handed Giants. Uranus hated his monstrous children, and as soon as each was born, he imprisoned them underground, somewhere deep inside Gaia. Eventually Uranus' son, the Titan Cronus, castrated Uranus, becoming the new ruler of the cosmos, but he did not release his brothers, the Cyclopes and the Hecatoncheires, from their imprisonment in Tartarus.  For this failing, Gaia foretold that Cronus would eventually be overthrown by one of his children, as he had overthrown his own father. To prevent this, as each of his children were born, Cronus swallowed them whole; as gods they were not killed, but imprisoned within his belly. His wife, Rhea, sought her mother's advice to avoid losing all of her children in this way, and Gaia advised her to give Cronus a stone wrapped in swaddling clothes. In this way, Zeus was spared the fate of his elder siblings, and was hidden away by his mother. When he was grown, Zeus forced his father to vomit up his siblings, who rebelled against the Titans. Zeus released the Cyclopes and Hecatoncheires, who became his allies. While the Hundred-Handed Giants fought alongside Zeus and his siblings, the Cyclopes gave Zeus his great weapon, the thunderbolt, with the aid of which he was eventually able to overthrow the Titans, establishing himself as the ruler of the cosmos.

Homer.

In Book 9 of the "Odyssey", Odysseus describes to his hosts the Phaeacians his encounter with the Cyclops Polyphemus. Having just left the land of the Lotus-eaters, Odysseus says "Thence we sailed on, grieved at heart, and we came to the land of the Cyclopes". Homer had already (Book 6) described the Cyclopes as "men overweening in pride who plundered [their neighbors the Phaeacians] continually", driving the Phaeacians from their home. In Book 9, Homer gives a more detailed description of the Cyclopes as: According to Homer, the Cyclopes have no ships, nor ship-wrights, nor other craftsman, and know nothing of agriculture. They have no regard for Zeus or the other gods, for the Cyclopes hold themselves to be "better far than they".  Homer says that "godlike" Polyphemus, the son of Poseidon and the nymph Thoosa, the daughter of Phorcys, is the "greatest among all the Cyclopes". Homer describes Polyphemus as a shepherd who: Although Homer does not say explicitly that Polyphemus is one-eyed, for the account of his blinding to make sense he must be. If Homer meant for the other Cyclopes to be assumed (as they usually are) to be like Polyphemus, then they too will be one-eyed sons of Poseidon; however Homer says nothing explicit about either the parentage or appearance of the other Cyclopes.

Euripides.

The Hesiodic Cyclopes: makers of Zeus' thunderbolts, the Homeric Cyclopes: brothers of Polyphemus, and the Cyclopean wall-builders, all figure in the plays of the fifth-century BC playwright Euripides. In his play "Alcestis", where we are told that the Cyclopes who forged Zeus' thunderbolts, were killed by Apollo. The prologue of that play has Apollo explain:  Euripides' satyr play "Cyclops" tells the story of Odysseus' encounter with the Cyclops Polyphemus, famously told in Homer's "Odyssey". It takes place on the island of Sicily near the volcano Mount Etna where, according to the play, "Poseidon’s one-eyed sons, the man-slaying Cyclopes, dwell in their remote caves." Euripides describes the land where Polyphemus' brothers live, as having no "walls and city battlements", and a place where "no men dwell". The Cyclopes have no rulers and no government, "they are solitaries: no one is anyone’s subject." They grow no crops, living only "on milk and cheese and the flesh of sheep." They have no wine, "hence the land they dwell in knows no dancing". They show no respect for the important Greek value of Xenia ("guest friendship). When Odysseus asks "are they god-fearing and hospitable toward strangers" ("φιλόξενοι δὲ χὤσιοι περὶ ξένους"), he is told: "most delicious, they maintain, is the flesh of strangers... everyone who has come here has been slaughtered."  Several of Euripides' plays also make reference to the Cyclopean wall-builders. Euripides calls their walls "heaven-high" ("οὐράνια"), describes "the Cyclopean foundations" of Mycenae as "fitted snug with red plumbline and mason’s hammer", and calls Mycenae "O hearth built by the Cyclopes". He calls Argos "the city built by the Cyclopes", refers to "the temples the Cyclopes built" and describes the "fortress of Perseus" as "the work of Cyclopean hands".

Callimachus.

For the third-century BC poet Callimachus, the Hesiodic Cyclopes Brontes, Steropes and Arges, become assistants at the forge of the smith-god Hephaestus. Callimachus has the Cyclopes make Artemis' bow, arrows and quiver, just as they had (apparently) made those of Apollo. Callimachus locates the Cyclopes on the island of Lipari, the largest of the Aeolian Islands in the Tyrrhenian Sea off the northern coast of Sicily, where Artemis finds them "at the anvils of Hephaestus" making a horse-trough for Poseidon:  And Artemis asks:

Virgil.

The first-century BC Roman poet Virgil seems to combine the Cyclopes of Hesiod with those of Homer, having them live alongside each other in the same part of Sicily. In his Latin epic "Aeneid", Virgil has the hero Aeneas follow in the footsteps of Odysseus, the hero of Homer's "Odyssey". Approaching Sicily and Mount Etna, in Book 3 of the "Aeneid", Aeneas manages to survive the dangerous Charybdis, and at sundown comes to the land of the Cyclopes, while "near at hand Aetna thunders". The Cyclopes are described as being "in shape and size like Polyphemus... a hundred other monstrous Cyclopes [who] dwell all along these curved shores and roam the high mountains." After narrowly escaping from Polyphemus, Aeneas tells how, responding to the Cyclops' "mighty roar": Later, in Book 8 of the same poem, Virgil has the Hesiodic Cyclopes Brontes and Steropes, along with a third Cyclopes which he names Pyracmon, work in an extensive network of caverns stretching from Mount Etna to the Aeolian Islands. As the assistants of the smith-god Vulcan, they forge various items for the gods: thunderbolts for Jupiter, a chariot for Mars, and armor for Minerva:

Apollodorus.

The mythographer Apollodorus, gives an account of the Hesiodic Cyclopes similar to that of Hesiod's, but with some differences, and additional details. According to Apollodorus, the Cyclopes were born after the Hundred-Handers, but before the Titans (unlike Hesiod who makes the Titans the eldest and the Hundred-Handers the youngest).  Uranus bound the Hundred-Handers and the Cyclopes, and cast them all into Tartarus, "a gloomy place in Hades as far distant from earth as earth is distant from the sky." But the Titans are, apparently, allowed to remain free (unlike in Hesiod). When the Titans overthrew Uranus, they freed the Hundred-Handers and Cyclopes (unlike in Hesiod, where they apparently remained imprisoned), and made Cronus their sovereign. But Cronus once again bound the six brothers, and reimprisoned them in Tartarus.  As in Hesiod's account, Rhea saved Zeus from being swallowed by Cronus, and Zeus was eventually able to free his siblings, and together they waged war against the Titans. According to Apollodorus, in the tenth year of that war, Zeus learned from Gaia, that he would be victorious if he had the Hundred-Handers and the Cyclopes as allies. So Zeus slew their warder Campe (a detail not found in Hesiod) and released them, and in addition to giving Zeus his thunderbolt (as in Hesiod), the Cyclopes also gave Poseidon his trident, and Hades a helmet (presumably the same cap of invisibility which Athena borrowed in the "Iliad"), and "with these weapons the gods overcame the Titans".  Apollodorus also mentions a tomb of Geraestus, "the Cyclops" at Athens upon which, in the time of king Aegeus, the Athenians sacrificed the daughters of Hyacinth.

Nonnus.

"Dionysiaca", composed in the 4th or 5th century BC, is the longest surviving poem from antiquity – 20,426 lines. It is written by the poet Nonnus in the Homeric dialect, and its main subject is the life of Dionysus. It describes a war that occurred between Dionysus' troops and those of the Indian king Deriades. In book 28 of the "Dionysiaca" the Cyclopes join with Dionysian troops, and they prove to be great warriors and crush most of the Indian king's troops.

Transformations of Polyphemus.

Depictions of the Cyclops Polyphemus have differed radically, depending on the literary genres in which he has appeared, and have given him an individual existence independent of the Homeric herdsman encountered by Odysseus. In the epic he was a man-eating monster dwelling in an unspecified land. Some centuries later, a dithyramb by Philoxenus of Cythera, followed by several episodes by the Greek pastoral poets, created of him a comedic and generally unsuccessful lover of the water nymph Galatea. In the course of these he woos his love to the accompaniment of either a cithara or the pan-pipes. Such episodes take place on the island of Sicily, and it was here that the Latin poet Ovid also set the tragic love story of Polyphemus and Galatea recounted in the Metamorphoses. Still later tradition made him the eventually successful husband of Galatea and the ancestor of the Celtic and Illyrian races.

Location.

From at least the fifth-century BC onwards, Cyclopes have been associated with the island of Sicily, or the volcanic Aeolian islands just off Sicily's north coast. The fifth-century BC historian Thucydides says that the "earliest inhabitants" of Sicily were reputed to be the Cyclopes and Laestrygones (another group of man-eating giants encountered by Odysseus in Homer's "Odyssey"). Thucydides also reports the local belief that Hephaestus (along with his Cyclopean assistants?) had his forge on the Aeolian island of Vulcano.  Euripides locates Odysseus' Cyclopes on the island of Sicily, near the volcano Mount Etna, and in the same play addresses Hephaestus as "lord of Aetna". The poet Callimachus locates the Cyclopes' forge on the island of Lipari, the largest of the Aeolians. Virgil associates both the Hesiodic and the Homeric Cyclopes with Sicily. He has the thunderbolt makers: "Brontes and Steropes and bare-limbed Pyracmon", work in vast caverns extending underground from Mount Etna to the island of Vulcano, while the Cyclops brethren of Polyphemus live on Sicily where "near at hand Aetna thunders".  As Thucydides notes, in the case of Hephaestus' forge on Vulcano, locating the Cyclopes' forge underneath active volcanoes provided an explanation for the fire and smoke often seen rising from them.

Etymology.

For the ancient Greeks the name "Cyclopes" meant "Circle-eyes" or "Round-eyes", derived from the Greek "kúklos" ("circle") and "ops" ("eye"). This meaning can be seen as early as Hesiod's "Theogony" (8th–7th century BC), which explains that the Cyclopes were called that "since a single circle-shaped eye was set in their foreheads". Adalbert Kuhn, expanding on Hesiod's etymology, proposed a connection between the first element "kúklos" (which can also mean "wheel") and the "wheel of the sun", producing the meaning "wheel (of the sun)-eyes". Other etymologies have been proposed which derive the second element of the name from the Greek "klops" ("thief") producing the meanings "wheel-thief" or "cattle-thief". Although Walter Burkert has described Hesiod's etymology as "not too attractive", Hesiod's explanation still finds acceptance by modern scholars.

Possible origins.

A possible origin for one-eyed Cyclopes was advanced by the palaeontologist Othenio Abel in 1914. Abel proposed that fossil skulls of Pleistocene dwarf elephants, commonly found in coastal caves of Italy and Greece, may have given rise to the Polyphemus story. Abel suggested that the large, central nasal cavity (for the trunk) in the skull might have been interpreted as a large single eye-socket.  A rare birth defect can result in foetuses (both human and animal) which have a single eye located in the middle of their foreheads. Students of teratology have raised the possibility of a link between this deformity and the myth of the one-eyed Cyclopes. However, in the case of humans with a single eye, they have a nose above the single eye, rather than below, as in ancient Greek depictions of the Cyclops Polyphemus.

In Greek mythology and later Roman mythology, the Cyclopes ( ;, "Kýklōpes", "Circle-eyes" or "Round-eyes"; singular Cyclops ;, "Kýklōps") are giant one-eyed creatures. Three groups of Cyclopes can be distinguished. In Hesiod's "Theogony", they are the brothers: Brontes, Steropes, and Arges, who provided Zeus with his weapon the thunderbolt. In Homer's "Odyssey", they are an uncivilized group of shepherds, the brethren of Polyphemus encountered by Odysseus. Cyclopes were also famous as the builders of the Cyclopean walls of Mycenae and Tiryns.

独眼巨人英文为“Cyclops”(希腊文:;复数:),音译库克洛普斯或赛克洛普斯,语意是圆眼。在希腊神话居住于西西里岛,其独眼长在额头上。