词条 | corn |
释义 | corn callus in skin disease, horny thickening of the skin on the foot or toes, produced by repeated friction or pressure. Extensive proliferation of the stratum corneum, the horny layer of the epidermis, results in a conical callus with its broad end on the surface and its point directed inward; the dense centre of this cone presses on sensory nerves, causing pain when direct pressure is applied. The corn's surface is usually hard and shiny, but corns between the toes may be soft and soggy from perspiration. Corns are treated by applying plasters of salicylic or dichloroacetic acid to the site after the core has been removed and the callus pared. They are likely to recur, however, unless the source of friction or pressure is eliminated by a change in footwear or in walking habits. Long-lasting corns may produce a bony spur that must be removed surgically. plant also called Indian corn, or maize in agriculture, cereal plant of the tribe Maydeae of the grass family Gramineae (Poaceae), originating in the Americas, and its edible grain. Since its introduction into Europe by Columbus and other explorers, corn has spread to all areas of the world suitable to its cultivation. Indians in the Americas taught colonists to grow the indigenous grains, which included some varieties of yellow corn that are still popular as food as well as varieties with red, blue, pink, and black kernels, often banded, spotted, or striped, that are regarded in modern times as ornamental. In the United States these variegated strains, traditionally used in autumn harvest decorations, are called Indian corn. In Great Britain, all maize grain is called Indian corn, in allusion to its origins. ![]() Commercial classifications, based mainly on kernel texture, include dent corn, flint corn, flour corn, sweet corn, and popcorn. Dent corn is characterized by a depression in the crown of the kernel caused by unequal drying of the hard and soft starch making up the kernel. Flint corn, containing little soft starch, has no depression. Flour corn, composed largely of soft starch, has soft, mealy, easily ground kernels. Sweet corn has wrinkled, translucent seeds; the plant sugar is not converted to starch as in other types. popcorn, an extreme type of flint corn characterized by small, hard kernels, is devoid of soft starch, and heating causes the moisture in the cells to expand, making the kernels explode. Improvements in corn have resulted from hybridization, based on crossbreeding of superior inbred strains. ![]() ![]() ![]() |
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