LIGHTERMAN'S BOTTOM 



686 



LILAC 



lation produced by the luminous body and propagated 

 in all directions with a velocity in a vacuum of about 

 186,500 miles per second. Maxwell s Electromagnetic 

 Theory supposes light to be an " electromagnetic dis- 

 turbance propagated by vibrations at right angles to 

 the direction of the ray, and taking place in the 

 ether, the strains or vibrations of which serve to pro- 

 pagate electromagnetic induction." L., Axial, light- 

 rays that are parallel to each other and to the optic 

 axis ; in microscopy the axial ray of the cone of light 

 must be parallel to the optic axis of the microscope. 

 L.-blue. See Pigments, Conspectus of. L. -brain, a 

 weak-minded person. L., Central. See L. , Axial. L., 

 Diffused, that reflected simultaneously from an infinite 

 number of surfaces, or that which has been scattered by 

 means of a concave mirror or lens. L., Dispersion of. 

 See L. , Spectrum of. L., Drummond, that produced 

 by heating lime to incandescence, as in the oxy-hydro- 

 gen flame. L., Electric, that produced by the passage 

 of electricity through a medium having high resistance, 

 such as the carbon-film of the incandescent light, or the 

 interval of air between the carbons of the arc light, 

 the medium of high resistance being heated to white- 

 ness. L. -green. See Pigments, Conspectus of. L.- 

 headed, giddy ; flighty ; delirious. L., Incandes- 

 cent, the incandescence produced as a result of the 

 resistance offered to the passage of an electric current 

 through a delicate film of carbon. L., Incident, or 

 Direct, that falling upon a surface or object. L., 

 Monochromatic, that which, on being analyzed by a 

 prism, consists approximately of waves of one length 

 only. L., Oblique, when parallel rays or the axial ray 

 of a cone of light forms an angle with the optic axis of 

 the microscope. See also Illumination , Oblique. L.- 

 red. Same as Ocher. L., Reflected, light thrown upon 

 the object and then thrown back from the object. L., 

 Reflection of, that property by which a ray of light 

 striking an object rebounds, or is sent out again. Rays 

 falling on a plane surface are reflected at an angle equal 

 to that of the incident ray. Objects are perceived 

 by the light reflected by such rays. L., Refraction of, 

 that property by which a ray or pencil of light, when 

 passing through media of different densities, is deflected 

 out of its course. See Law of Refraction. L. -sense, 

 the faculty by which different degrees of light or 

 brightness may be distinguished. L., Spectrum of. 

 See Spectrum, and Wave-lengths. L.-spot, Triangu- 

 lar, the pyramidal spot of light seen on the normal tym- 

 panic membrane, having its apex at the umbo, and its 

 base toward the periphery. L., To Feel ; quickening ; 

 the sensation conveyed to the mother by the move- 

 ments of the fetus in utero. L., Transmitted, 

 the light passing through an object. 



Lighterman's Bottom. Inflammation of the bursa 

 over the tuberosity of the ischium, from much 

 sitting. 



Lighting (lit'-intf) [ME., lihtinge, lighting]. The pro- 

 per arrangement of the optic parts of a microscope, 

 with the mirror so that the field is equally illuminated. 



Lightning (lit'-ning) [ME., light, light]. An at- 

 mospheric discharge of electricity. In the form 

 commonly known as "chain" or "bolt" light- 

 ning, the electricity has an extremely high potential, 

 and a stroke under such circumstances is invariably 

 fatal when the discharge passes through a living body. 

 The form known as " sheet " lightning is a "brush " 

 discharge of low potential, and is harmless. L. Ca- 

 tarrh. Synonym of Influenza. L. Pains, the lancinat- 

 ing pains of locomotor ataxia, usually occurring in the 

 thighs, but also at times in the arms, head, and trunk. 

 They are severe and come on in paroxysms, and may 

 or may not follow the course of a nerve or nerves. 



Lights (lits) [ME., light, light]. The lungs, so-called 

 because of their light weight. 



Lignaloes [lig-nal' -oz) [lignum aloes']. Same as Agal- 

 lochum and Eagle-wood, q. v. 



Lignatile (lig'-nat-il) [lignum, wood]. Same as Lig- 

 nicole. 



Ligneous (lig'-ne-us) [lignum, wood]. Woody, or 

 having a woody texture. 



Lignerolle's Amputation. See Operations, Table of. 



Lignicole (lig' -nik-ol) Lignicoline (lig-nik' -o-lin) [lig- 

 num, wood; colere, to dwell]. In biology, growing 

 upon wood. 



Lignification (lig-nifik-a'-shun) [lignum, wood; 

 facere, to make]. The process of turning into wood; 

 sometimes also applied to amyloid degeneration, q. v. 



Ligniform [lig' -nif-orm) [lignum, wood ; forma, form]. 

 Resembling wood. 



Lignin (lig'-nin) [lignum, wood], C 19 H 24 O ]0 (?). A 

 modification of cellulose, constituting the greater por- 

 tion of the weight of most dry wood. It has not been 

 isolated. L., Tests for ; phloroglucin gives a violet 

 color to lignified cell-walls. Anilin sulphate, in 

 slightly acidulated solution, gives a bright-yellow color. 



Lignite {lig' -nit) [lignum, wood]. Brown coal; im- 

 perfectly formed coal, or that in which the original 

 form of the wood is so distinctly preserved that it can 

 be readily distinguished by the eye. It is a source of 

 certain members of the paraffin group of hydro- 

 carbons. See Coal. 



Lignivorous (lig-niv 1 '-or-us) [lignum, wood ; vorare, 

 to eat, to devour]. Applied to such insect larvae, 

 ants, beetles, etc., as devour wood. 



Lignoin (lig'-no-in) [lignum , wood] , C 20 H 23 NO 8 . An 

 alkaloid found in certain Cinchonas. 



Lignose (lig'-nos). See Cellulose. 



Lignum (lig'-num) [L.]. Wood. L. agallochum, 

 aloes wood. L. benedictum, guaiac wood. L. 

 cedrium, cedar wood. L. vitae. See Guaiacum. 



Ligroin (lig'-ro-in) [origin obscure]. A product ob- 

 tained from petroleum, boiling at from8o°to I20°C, 

 and having a specific gravity of from .710 to .73°- ^ 

 is used in pharmacy for solvent purposes, and for 

 burning in sponge-lamps. 



Ligula (lig'-u-lah) [dim. of lingua, a tongue]. A little 

 tongue or tongue-shaped organ ; the epiglottis ; the 

 clavicle ; the tenia of the fourth ventricle, called also 

 ala pontis or ponticuhis. Also, a name given to 



■ the tongue of an articulate. See Lingula. In biology, 

 applied to various strap-shaped organs or parts, as the 

 corolla- blade in a plant, or the long tongue-like organ 

 of hymenopterous insects. Also called Ligule. 



Ligulate (lig'-u-ldt) [ligula, from lingua, tongue]. 

 Shaped like a small tongue ; strap-shaped. 



Ligule (lig'-ul) [ligula, a variety of lingula, a little 

 tongue; a strap]. Same as Ligula. 



Liguliform (lig-u'-lif-orm). See Ligulate. 



Ligulin (lig'-u-lin) [ligula, a little tongue]. The col- 

 oring-matter of Levisticum officinale, Koch, and of the 

 berries of the common privet (Ligustrum vulgart). 

 With limestone water it strikes a bright-red cold 

 changing to blue, whence it has been used as a test 

 for the presence of limestone in water. 



Ligusticum (li-gus' '-tik-um) [TiiyvartKOg, Ligurian 

 genus of umbelliferous plants : lovage. L. actai- 

 folium is carminative and stimulant, as is also L. 

 apiifolium of N. America. Unof. 



Ligustrum {li-gus' -trum) [L.]. A genus of oleaceons 

 shrubs; privets. L. vulgare, the common priv< I 

 astringent leaves and bark, and cathartic berries. I 



Lilac {li'-lok) [Ar., lilak, lilac]. The haves and fruit 

 of Syringa vulgaris, a bitter tonic, with reputed anti- 

 periodic properties. Unof. 



