Hemacandra N.ha-mo-'chon-droV orig. Candradeva (b. 1088, Dhandhuka, Gujarat, India—d. 1172, Gujarat) Sage of Jainism. His birth is said to have been attended by auspicious omens, and he was educated by Jain priests. Ordained in 1110, he became an adviser to King Kumarapala in 1125, and by converting the king he firmly entrenched Jainism in Gujarat. His many writings include works on almost every branch of Indian philosophy and the sciences as well as literary writings such as his Sanskrit epic, Lives of the Jain Elders. In accordance with Jain tradition, he fasted to death.
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860 I hemangioma ► hemp
hemangioma V.he-.man-je-'o-msN Congenital benign tumour made of blood vessels in the skin. Capillary hemangioma (nevus flammeus, port- wine stain), an abnormal mass of capillaries on the head, neck, or face, is pink to dark bluish-red and even with the skin. Size and shape vary. It becomes less noticeable or disappears with age. Immature hemangioma (hemangioma simplex, strawberry mark), a reddish nub of dilated small blood vessels, enlarges in the first six months and may become ulcerated but usually recedes after the first year. Cavernous hemangioma, a rare, red- blue, raised mass of larger blood vessels, can occur in skin or in mucous membranes, the brain, or the viscera. Fully developed at birth, it is rarely malignant. Hemangiomas can often be removed by cosmetic surgery.
hematite Vhe-mo-.tltV or haematite Heavy and relatively hard oxide mineral, ferric oxide (Fe 2 0 3 ), that constitutes the most important iron ore because of its high iron content and its abundance. Much hematite (from the Greek word meaning “blood,” for its red colour) occurs in a soft, fine¬ grained, earthy form called red ocher or ruddle. Red ocher is used as a paint pigment; a purified form, rouge, is used to polish plate glass. The world’s largest production comes from the Hamersley Range in western Australia.
hematology \ l he-m3-'ta-l3-je\ Branch of medicine concerned with the nature, function, and diseases of the blood. It covers the cellular and serum composition of blood, the coagulation process, blood-cell formation, hemoglobin synthesis, and disorders of all these. Marcello Malpighi, in the 17th century, was the first to examine red blood cells (erythrocytes). In the 18th century, the British physiologist William Hewson (1739-74) exam¬ ined the lymphatic system and blood clotting. In the 19th century, the bone marrow was recognized as the site of blood-cell formation, and diseases of the blood such as anemia and leukemia were identified. In the early 20th century, the ABO blood-group system was discovered and the role of nutri¬ tion in blood formation was studied. Post-World War II studies have delved further into the nature of blood diseases and improved treatments and have examined hemoglobin synthesis and the role of platelets in blood coagulation.
hematuria \,he-m3- , tur-e-9\ Blood in the urine. It usually indicates injury or disease of the kidney or another structure of the urinary system or possibly, in males, the reproductive system. It may result from infec¬ tion, inflammation, tumours, kidney stones, or other disorders. How the blood looks and when it appears in the urine stream reflect whether it originates in the urethra, the bladder, or the kidney.
Hemingway, Ernest (Miller) (b. July 21, 1899, Cicero [now in Oak Park], Ill., U.S.—d. July 2, 1961,
Ketchum, Idaho) U.S. writer. He began work as a journalist after high school. He was wounded while serv¬ ing as an ambulance driver in World War I. One of a well-known group of expatriate writers in Paris, he soon embarked on a life of travel, skiing, fishing, and hunting that would be reflected in his work. His story col¬ lection In Our Time (1925) was fol¬ lowed by the novel The Sun Also Rises (1926). Later novels include A Farewell to Arms (1929) and To Have and Have Not (1937). His life¬ long love for Spain (including a fas¬ cination with bullfighting) led to his working as a correspondent during the Spanish Civil War, which resulted in the novel For Whom the Bell Tolls (1940). Other short-story collections include Men Without Women (1927), Winner Take Nothing (1933), and The Fifth Column (1938). He lived primarily in Cuba from c. 1940, the locale of his novella The Old Man and the Sea (1952, Pulitzer Prize). He was awarded the Nobel Prize for Literature in 1954. He left Cuba shortly after its 1959 revolution; a year later, depressed and ill, he shot himself. The succinct and concentrated prose style of his early works strongly influenced many British and American writers for decades.
hemispheric asymmetry See laterality
hemlock Any of 10 species of coniferous evergreen trees that make up the genus Tsuga, in the pine family, native to North America and central and eastern Asia. Some are important timber trees, and many are popular ornamentals. Other plants commonly called hemlock include ground hem¬ lock (see yew) and poison hemlock and water hemlock (parsley family). A true hemlock is a tall, pyramidal tree with purplish or reddish-brown bark, slender horizontal or drooping branches, and short, blunt leaves that grow from woody cushionlike structures on the twigs.
hemodialysis See dialysis
hemoglobin Vhe-mo-.glo-bonV Protein in the blood of many animals (in vertebrates it is in red blood cells) that transports oxygen from the lungs to the tissues. It is bright red when combined with oxygen and purple- blue in the deoxygenated state. Each molecule is made up of a globin (a type of protein) and four heme groups. Heme, a complex heterocyclic compound, is an organic molecule derived from porphyrin with an iron atom at the centre. Variant hemoglobins (see sickle-cell anemia; hemoglobinopa¬ thy) can be used to trace past human migrations and to study genetic rela¬ tionships among populations.
hemoglobinopathy \ l he-m3- l glo-b9- , na-p3-the\ Any of a group of disorders caused by genetic abnormality of the hemoglobin molecule. The most prominent types are sickle-cell anemia and thalassemia, a set of dis¬ orders whose symptoms range from none to fatal anemia.
hemolytic disease of the newborn See erythroblastosis fetalis
hemophilia V.he-mo-'fi-le-oV Hereditary bleeding disorder caused by deficiency of a coagulation factor. Lack of factor VIII causes classic hemophilia; other types are caused by deficiency of factor IX or XI. The first two are transmitted by sex-linked heredity; the third has dominant inheritance and occurs in females as well as males. Spontaneous bleed¬ ing may occur. Even trivial injury can cause life-threatening blood loss. Drugs can be given to stop bleeding. Heavy blood loss requires blood transfusions.
hemorrhage Vhe-mo-rijV Escape of blood from blood vessels into sur¬ rounding tissue. When a vessel is injured, hemorrhage continues as long as the vessel remains open and the pressure in it exceeds the pressure outside of it. Normally, coagulation closes the vessel and stops the bleed¬ ing. Uncontrolled hemorrhage can result from anticoagulant therapy, hemophilia, or severe blood-vessel damage, leading to excessive blood loss and shock.
hemorrhagic X.he-ms-Ta-jikV fever Disease with high fever and hem¬ orrhage of internal organs and into the skin. It is caused by several kinds of virus (of which Ebola, dengue, and yellow fever are the best known), some carried by ticks, mosquitoes, or animals. Initial symptoms may include head, muscle, joint, and abdominal pain; nausea and vomiting; sweating and thirst; and coldlike symptoms. It comes on suddenly and can cause severe kidney damage. Patients who are severely ill may also experience shock and neurologic effects.