impressment Enforcement of military or naval service on unwilling men. Until the early 19th century, it flourished in port towns everywhere, as “recruiters” searched through waterfront boardinghouses, brothels, and taverns. They often chose vagabonds or prisoners. Impressed men were forced into service through violence or coercion and were held to their duty by brutal discipline. In the early 19th century, Royal Navy ships halt¬ ing U.S. vessels to search for British deserters frequently impressed natu¬ ralized U.S. citizens, one cause of the War of 1812. Impressment declined in the 19th century as states adopted more systematic recruiting methods. See also conscription.
imprinting Form of learning wherein a very young animal fixes its attention on the first object with which it has visual, auditory, or tactile experience and thereafter follows that object. In nature, the object is almost always a parent; in experiments, other animals and inanimate objects have been used. Imprinting has been studied extensively only in birds, but a comparable form of learning apparently takes place among many mammals and some fishes and insects. Ducklings and chicks, which can imprint in a few hours, lose receptivity to imprinting stimuli within 30 hours of hatching.
improvisation Creation of music in real time. Improvisation usually involves some preparation beforehand, particularly when there is more than one performer. Despite the central place of notated music in the Western tradition, improvisation has often played a role, from the earli¬ est organum through the use of continuo (partially improvised accompa¬ niment played on a bass line) in the 17th and 18th centuries. It has taken forms such as creation of a melody over a bass line for dancing, elabo¬ rate ornamentation added to a repeated section in an aria, keyboard varia¬ tions on popular songs, concerto cadenzas, and free solo fantasias. Perhaps at its lowest ebb in the 19th century, improvisation returned to concert music in “experimental” compositions and in “authentic” performances of older music. Its most important contemporary Western form is jazz. It is also a defining feature of the raga.
in vitro fertilization (IVF) \in-'ve-tro\ or test-tube conception
Procedure, used to overcome infertility, in which eggs are removed from a woman, fertilized with sperm outside the body, and inserted into the uterus of the same or another woman. The first child thus conceived was bom in 1978. IVF includes extraction of eggs, collection of sperm, fertiliza¬ tion in culture, and introduction into the uterus at the eight-cell stage. In a successful procedure, the embryo is implanted in the uterine wall, and pregnancy begins. The most com¬ mon problem is failed implantation.
IVF has been a source of moral, ethi¬ cal, and religious controversy since its development.
Inari \e-'na-re\ In Japanese mythol¬ ogy, the patron god of rice cultiva¬ tion and prosperity. He was worshiped especially by merchants and tradesmen, and he also served as patron deity of swordsmiths, broth¬ els, and entertainers. Inari was vari¬ ously depicted as a bearded old man riding a fox or as a woman with long hair, carrying sheaves of rice. The fox is sometimes identified as his messenger. The god’s most popular shrine is the Fushimi Inari Shrine near Kyoto.
inbreeding Mating of closely related individuals. The opposite is out- breeding, the mating of unrelated organisms. Inbreeding is useful in keep¬ ing desirable characteristics or eliminating undesirable ones, but it often results in decreased vigour, size, and fertility of the offspring because of the combined effect of harmful genes that were recessive in both parents (see recessiveness). The closest type of inbreeding is self-fertilization. In linebreeding, mates are selected on the basis of their relationships to a certain superior ancestor. The backcross (crossing a first-generation hybrid with one of the parental types) is a common method of inbreed¬ ing.
Inca Group of South American Indians who ruled an empire that extended along the Pacific coast and Andes Mountains from what is now northern Ecuador to central Chile. According to tradition (the Inca left no written records), the founder of the Incan dynasty led the tribe to Cuzco, which became their capital. Under the fourth emperor, they began to expand, and under the eighth they began a program of permanent con¬ quest by establishing garrisons among the conquered peoples. Under Topa Inca Yupanqui and his successor, the empire reached its southernmost and northernmost extent. By the early 16th century the Inca controlled an empire of some 12 million subjects. They constructed a vast network of roads, their architecture was highly developed, and the remains of their irrigation systems, palaces, temples, and fortifications are still in evidence throughout the Andes. Incan society was highly stratified and featured an aristocratic bureaucracy. Their pantheon, worshiped in a highly organized state religion, included a sun god, a creator god, and a rain god. The Incan empire was overthrown in 1532 by the Spanish coNQUiSTADORes, who made great use of the Incan road system during their conquests. The Inca’s descendants are the Quechua-speaking peasants of the Andes (see Que- chua). In Peru nearly half the population is of Incan descent. They are primarily farmers and herders living in close-knit communities. Their Roman Catholicism is infused with belief in pagan spirits and divinities. See also Andean civilization; Atahuallpa; Aymara; Chimu; Francisco Pizarro.
incandescent lamp Any of various devices that produce light by heating a suitable material to a high temperature. In an electric incandes¬ cent lamp, or lightbulb, a filament is enclosed in a glass shell that is either evacuated or filled with an inert gas. The filament gives off light when heated by an electric current. The first practical electric incandescent lamps were independently produced in the late 1870s by Joseph Swan and Thomas Alva Edison. Edison has received the major credit because of his development of the power lines and other equipment needed for a light¬ ing system. Inefficient in comparison with fluorescent lamps and electric discharge lamps, incandescent lighting is today reserved mainly for domes¬ tic use. See also halogen lamp.
Incarnation Central Christian doctrine that God became man in the form of Jesus, the son of God and the second person of the Holy Trinity. In Jesus the divine and human nature are joined but neither is changed or diminished. This difficult doctrine gave rise to a variety of heresies, some denying Jesus’s divine nature, others his human nature. For orthodox believers the conflict was settled at the Councils of Nicaea (ad 325) and Chalcedon (ad 451).
incense Grains of resins (sometimes mixed with spices) that burn with a fragrant odor, widely used as religious offerings. Historically, the chief substances used as incense have been resins such as frankincense and myrrh, along with fragrant wood and bark, seeds, roots, and flowers.
incest Sexual relations between persons who, because of the nature of their kinship ties, are prohibited by law or custom from intermarrying. The incest taboo is generally universal, although it is imposed differently in different societies. Usually, the closer the genetic relationship between two people, the stronger and more highly charged is the taboo prohibit¬ ing or discouraging sexual relations. Some sociobiologists consider that inbred populations have diminished reproductive success and become gene pools for hereditary disorders. Some cultural anthropologists argue instead that the incest prohibition, with the corresponding rules of exogamy, acts to require males to seek sexual and marital partners outside the group, thereby establishing useful alliances. Other theories emphasize the need to control sexual jealousies within the family or to prepare chil¬ dren to function with restraint in adult society. No single explanation seems satisfactory, causing some to question whether incest should be treated as a unitary subject. Most cases of incest that come before crimi¬ nal courts concern sexual intercourse between fathers and relatively young daughters (see child abuse).