ANGILBERT, ST., the most celebrated poet of his age, secretary and friend of Charlemagne, whose daughter, Bertha, he married. In the latter part of his life he retired to a monastery, of which he became abbot. Died 814.
ANGINA PECTORIS (an´ji-na pek´to-ris), or HEART-SPASM, a disease characterized by an extremely acute constriction, felt generally in the lower part of the sternum, and extending along the whole side of the chest and into the corresponding arm, a sense of suffocation, faintness, and apprehension of approaching death: seldom experienced by any but those with organic heart-disease. The disease rarely occurs before middle age, and is more frequent in men than in women. Those liable to attack must lead a quiet, temperate life, avoiding all scenes which would unduly rouse their emotions. The first attack is occasionally fatal, but usually death occurs as the result of repeated seizures. The paroxysm may be relieved by opiates, or the inhalation, under due precaution, of anæsthetic vapours.
ANGIOSPERM (an´ji-o-sp[.e]rm), a term for any plant which has its seeds enclosed in a seed-vessel. Exogens are divided into those whose seeds are enclosed in a seed-vessel, and those with seeds produced and ripened without the production of a seed-vessel. The former are _angiosperms_, and constitute the principal part of the species; the latter are _gymnosperms_, and chiefly consist of the Coniferæ and Cycadaceæ.
ANGLE, the point where two lines meet, or the meeting of two lines in a point. A _plane rectilineal angle_ is formed by two straight lines which meet one another, but are not in the same straight line; it may be considered the degree of opening or divergence of the two straight lines which thus meet one another. A _right angle_ is an angle formed by a straight line falling on another perpendicularly, or an angle which is measured by an arc of 90 degrees. When a straight line, as A B (fig. 1), standing on another straight line C D, makes the two angles A B C and A B D equal to one another, each of these angles is called a _right angle_. An _acute angle_ is that which is less than a right angle, as E B C. An _obtuse angle_ is that which is greater than a right angle, as E B D. Acute and obtuse angles are both called _oblique_, in opposition to right angles. _Exterior_ or _external angles_, the angles of any rectilineal figure without it, made by producing the sides; thus, if the sides A B, B C, C A of the triangle A B C (fig. 2) be produced to the points F D E, the angles C B F, A C D, B A E are called _exterior_ or _external angles_. A _solid angle_ is that which is made by more than two plane angles meeting in one point and not lying in the same plane, as the angle of a cube. A _spherical angle_ is an angle on the surface of a sphere, contained between the arcs of two great circles which intersect each other.