valve (valv)

[ Swift thro' the valves the visionary fair Repa 'd. Pope , Ody ey, iv. 1093. Heavily closed, with a jarring sound, the valves of the barn. doors. Long fellow , Evangeline, i. 2. C IMG:content-1681.png:[ocr errors] IMG:content-1682.png:[ocr errors] a, the valvate estivation of the corolla of Ampelopsis quin que folia, b, the flower of the same, open; c, stamen of Berberis vulgar is, with the anther dehiscing with valves; d, pod of Barb are a vulgar is with valvate dehis cence. 2. Any device or appliance used to control the flow of a liquid, vapor, or gas, or loose material in bulk, through a pipe, pa ageway, outlet, or inlet, in any form of containing ve el. In this wide and general sense, the term includes air-, gas-, steam-, and water-cocks of any kind, water-gates, air-gates, and keys to musical wind-instruments. Rotary valves are valves in which the leaf, disk, plug, or other device used to close the pa age is made to revolve for opening or closing (the common stop-cock being an illustration); lifting - valves are those in which the ball, cone, or other stopper is lifted or raised clear of the valve-seat by pre ure (usually that of the gas, steam, or liquid in the pipe) from below, the poppet-, ball-, and safety - valves being amples; hinged valves constitute a large cla used in both air and water-pipes, as the butterfly - valves, clack valves, and other forms in which the leaf or plate of the valve is fastened on one side to the valve-seat or open ing. Springs are sometimes used to keep such valves closed. Sliding valves are those in which the gate or leaf slides aside to open the valve-way, the D - valve and some forms of water and gas-main valves being examples. The long-hinged valves of a pipe-organ, and the round stoppers operated by keys, as in the flute and other instruments, are called key - valves. The names by which valves are distinguished are often descriptive of the shape or motion of the valves, of their use, or of the method by which they are operated, as globe - valve, screw- valve, blow - through valve, relief- valve, throttle - valve. In a trade sense, valves appear to be distinguished from cocks. A cock is a small plug-valve operated by hand. Other valves moved by screws or levers, or operated by power through some machinery, all self-acting appliances, and all large or complicated gates, stoppers, or cocks, are called valves. The universal use of steam, gas, and water has led to the invention of a great variety of valves. In musical wind-instruments of the trumpet cla , the valve is a device for changing the direction and length of the air-column so as to alter the pitch of the tone. The two forms most in use are the piston and the rotary valve-the former being a perforated plunger working in a cylindrical case, and the latter a four-way cock, both being operated by the fingers of the player's right hand. The result of using a valve is to add to the main tube of the instrument a sup IMG:content-1683.png:[blocks in formation] silicified membrane or shell is called a valve . valved (valvd), a. [ valve + -ed2.] Having See cuts under Marsilea , septicidal , and silicle . a valve or valves, in any sense; valvate; val- -5. In conch ., one of the two or more separa- ble pieces of which the shell may consist, or the whole shell when it A B is in one piece; each shell, right and left, of ordinary bivalves, and each shell, dorsal and ventral, of brachiopods. See bi valve, multi valve, uni valve, equivalve, inequivalve, and cuts under Caprotinidæ, Chamidæ, integropal liate, and sinupal- showing hinge area ( V, ventral liate.-6. In entom., Valves of a Brachiopod ( Leptæna ). A, both valves, seen edgewise, B, dorsal valve, interior. a covering plate or sheath of any organ, generally one of a pair of plates which unite to form a tube or vagina, as those covering the external sexual organs, ovipositor, etc. - Acce ory, aortic, back-pre ure, basal valve. See the IMG:content-1684.png:[blocks in formation] guarding either auriculoventricular orifice of heart: on the right side the tricuspid, on the left the mitral. See cuts under heart. - Bauhinian valve. Same as ileocæcal valve. - Bicuspid valve. Same as mitral valve. - Blow through, brake-shoe, conical valve. See blow - through, der valvula. - Coronary valve. See coronary. - Cylindrical valve. See cylindric. - Delivery-valve. See de Connivent valves. See valvulæ conniventes, un livery.-Eustachian valve. See - Gridiron bat, Diclidurus alb us, the end of whose tail occupies a valve-like formation of the interfemoral membrane. valve-view (valv'vū), n. and a. I. n. In bot., the valval aspect of a diatom. Also called side view. See valval. II. a. Noting a position in which a valve view is presented; valval. valve formed by the mucous membrane at the meatal end valve See gridiron . - Hasner's valve, an imperfect of the nasal duct.-Heister's valve, folds of mucous valviferous (val-vif'e-rus), a. [L. valva , membrane at the neck of the gall-bladder and in the cystic duct, which present appearance valve. See cut under stomach.-Hydraulic, hypopygial, ileocæcal, inferior valve. See the adjectives. leocolic valve. Same as ileocæcal valve. - Kingston's valve, a conical valve forming the outlet of the blow-off pipe of a marine engine. It opens through the side of a ve el by turning a screw. -Long valve, in a steam-engine, same as long slide (which see, under slide ). - Low-water valve, a valve which opens automatically and allows steam to escape when the water in an engine-boiler is reduced too low for safety. – Mitral valve, a valve formed by two triangular folds of the endocardium, or inner lining of the heart, situated at the opening between the left ventricle and the auricle, and serving to prevent regurgitation of blood into the latter cavity. Also bicuspid valve. See cut under heart. Oral valves. See oral. Oscillating valve, a steam-valve which reciprocates on a pivot. It is frequently used with oscillating steam-engines. - Overpre ure valve. See overpre ure.-Pocketed valve, a valve fitting into a depre ion or pocket. - Pot-lid valve. (a) A cap-formed valve which shuts down like a cover upon a port or the end of a pipe. (b) The cover of the air pump of a steam-engine. E. H. Knight. - Pulmonary valves. See pulmonary, and cut under heart. - Pulmonic valves, Same as pulmonary valves. - Pyloric valve. ( a ) A small tubercle situated at the anterior angle of the trigonum of the bladder. (b) Any formation serving to obstruct or close the pyloric orifice of the stomach. A pylorus may have a valvular construction, or a muscular sphincter may surround the orifice. See pylorus, 2 (b). - Regulator-valve, a throttle-valve. - Reverse valve, in boilers, a valve opening inward to the pre ure of the atmosphere when there is a negative pre ure in the boiler.-Rotary valve. See rotary. - Semilunar aortic valve, semilunar pulmonary valve. See semilunar, and cut under heart.- Semilunar valve of the brain. Same as valve of Vieu ens. - Sigmoid valve. See sigmoid. tone of the whole is lowered by some definite interval. The number of valves is commonly three, the first lowering the fundamental tone a whole step (and all its harmonics proportionally), the second lowering it a half-step, and the third a step and a half. A fourth valve is sometimes added on large instruments, lowering the pitch two steps and a half; and five and six valves have occasionally been tried. Two or more valves are used simultaneously with combined effect. Valves are more or le demanded to compensate for the incompletene of the scale of all instruments of this family, and to provide for rapid changes of tonality. They are also useful in particular cases to remedy the inaccuracy for concerted music of certain of the regular harmonic series of tones. Their extended application has greatly developed the capacity of all kinds of bra instruments for rapid and unrestricted execution. But on the other hand valves and supplementary crooks cannot always give exactly accurate intonation, and the angles which they more or le nece itate in the air-column tend to injure the purity of the tones. Various compensations for these drawbacks have been attempted, with some succe ; but valve-instruments are still seldom used in the orchestra, while they are numerous in military bands. See piston, 2, and compare key1, 4 (a). See cuts under back - pre ure, ball - cock, conical, organ, reed-organ, twin- valve, slide - valve, steam-engine, safety-valve. 3. In an at. and zoöl., a membranous part, fold, or thin layer which resembles a valve, or actually serves as a valve in connection with the flow of blood, lymph, or other fluid; a valva or valvula: as, the valve of Vieu ens in the brain; the connivent valves of Kerkring in the intestine; valves of the heart, of the veins, etc. See cuts under bulb, Crinoidea, heart, lymphatic, and vein.-4. In bot., in flowering plants, one of the segments into which a capsule dehisces, or which opens like a lid in the dehiscence of certain anthers. In Diatom aceæ each half of the steam-engine or steam-pump, a valve moved by direct steam-pre ure, without the intervention of an eccentric, crank, cam, or valve-stem. See cut under rock- drill. Thebes i an valve. See Thebes i an. -Tricuspid valve. See tricuspid.-Twin valve. See twin1. - Under shut valve, a valve placed beneath the sole-plate of a pump or other mechanism, as distinguished from one placed above the plate, and closed by a force acting from below upward. E. H. Knight. Valve of Amu at. Same as Heister's valve.- Valve of Bauhin, Same as ileocæcal valve. Valve of Hasner. See Hasner's valve. - Valve of Tarinus. Same as valve of Vieu ens. - Valve of Thebes i us. See Thebes i an valve. - Valve of Tulpius. Same as ileo cæcal valve. Valve of Varolius, Same as ileocæcal valve. Valve of Vieu ens the delicate transparent roof of the anterior part of the fourth ventricle, continuous anteriorly with the post optic i, posteriorly with the cerebellum; the superior medullary velum. - Valves of Kerkring, the valvulæ conniventes of the intestine (which see, under valvula ).- Valves of the heart. See coronary , mitral , semilunar ( aortic, pulmonary ), Thebes i an, and tricuspid valve; also cut under heart. - Valves of the lymphatics. See lymphatic, n. (with cut).-Valves of the veins, folds of the lining membrane of the veins, most numerous in those of the lower extremities, which serve to impede or prevent the backward flow of blood in those ve els.