Part 560

Lac*ton"ic (?), a. [From Lactone.] (Chem.) Of, pertaining to, or derived from, lactone.

Lac*ton"ic, a. [From Lactose.] (Chem.) Pertaining to, or designating, an acid obtained by the oxidation of milk sugar (lactose).

Lac`to*pro"te*in (?), n. [L. lac, lactis, milk + E. protein.] (Physiol. Chem.) A peculiar albuminous body considered a normal constituent of milk.

Lac"to*ry (?), a. Lactiferous. [Obs.] "Lactory or milky plants." Sir T. Browne.

Lac"to*scope (?), n. [L. lac, lactis + scope.] An instrument for estimating the amount of cream contained in milk by ascertaining its relative opacity.

Lac"tose` (?), n. 1. (Physiol. Chem.) Sugar of milk or milk sugar; a crystalline sugar present in milk, and separable from the whey by evaporation and crystallization. It has a slightly sweet taste, is dextrorotary, and is much less soluble in water than either cane sugar or glucose. Formerly called lactin.

2. (Chem.) See Galactose.

||Lac*tu"ca (?), n. [L., lettuce. See Lettuce.] (Bot.) A genus of ||composite herbs, several of which are cultivated for salad; lettuce. || ||Lac`tu*ca"ri*um (?), n. [NL., fr. L. lactuca lettuce.] The ||inspissated juice of the common lettuce, sometimes used as a ||substitute for opium. || Lac*tu"cic (?), a. (Chem.) Pertaining to, or derived from, the juice of the Lactuca virosa; -- said of certain acids.

Lac*tu"cin (?), n. [From Lactuca: cf. F. lactucine.] (Chem.) A white, crystalline substance, having a bitter taste and a neutral reaction, and forming one of the essential ingredients of lactucarium.

Lac*tu"cone (?), n. [From Lactuca.] (Chem.) A white, crystalline, tasteless substance, found in the milky sap of species of Lactuca, and constituting an essential ingredient of lactucarium.

Lac`tu*ram"ic (&?;), a. [Lactic + urea + amic.] (Chem.) Pertaining to, or designating, an organic amido acid, which is regarded as a derivative of lactic acid and urea.

Lac"tyl (?), n. [Lactic + - yl.] (Chem.) An organic residue or radical derived from lactic acid.

||La*cu"na (l*k"n), n.; pl. L. Lacunæ (#); E. Lacunas (#). [L., ditch, ||pit, lake, orig., anything hollow. See Lagoon.] 1. A small opening; a ||small pit or depression; a small blank space; a gap or vacancy; a ||hiatus. || 2. (Biol.) A small opening; a small depression or cavity; a space, as a vacant space between the cells of plants, or one of the spaces left among the tissues of the lower animals, which serve in place of vessels for the circulation of the body fluids, or the cavity or sac, usually of very small size, in a mucous membrane.

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{ La*cu"nal (l*k"nal), La*cu"nar (l*k"nr), } a. Pertaining to, or having, lacunæ; as, a lacunar circulation.

La*cu"nar, n.; pl. E. Lacunars (#), L. Lacunaria (#). [L.] (Arch.) (a) The ceiling or under surface of any part, especially when it consists of compartments, sunk or hollowed without spaces or bands between the panels. Gwilt (b) One of the sunken panels in such a ceiling.

La*cune" (l*kn"), n. [F.] A lacuna. [R.] Landor.

{ Lac"u*nose` (?), La*cu"nous (?), } a. [L. lacunosus full of holes or hollows; cf. F. lacuneux. See Lacuna.] (Biol.) Furrowed or pitted; having shallow cavities or lacunæ; as, a lacunose leaf.

{ La*cus"tral (?), La*cus"trine (?), } a. [L. lacus lake: cf. F. lacustral, lacustre.] Found in, or pertaining to, lakes or ponds, or growing in them; as, lacustrine flowers.

Lacustrine deposits (Geol.), the deposits which have been accumulated in fresh-water areas. -- Lacustrine dwellings. See Lake dwellings, under Lake.

Lac"work` (?), n. Ornamentation by means of lacquer painted or carved, or simply colored, sprinkled with gold or the like; -- said especially of Oriental work of this kind.

Lad (ld), obs. p. p. of Lead, to guide. Chaucer.

Lad (ld), n. [OE. ladde, of Celtic origin; cf. W. llawd, Ir. lath. &radic;123. Cf. Lass.] 1. A boy; a youth; a stripling. "Cupid is a knavish lad." Shak.

There is a lad here, which hath five barley loaves and two small fishes.

John vi. 9.

2. A companion; a comrade; a mate.

Lad's love. (Bot.) See Boy's love, under Boy.

Lad"a*num (?), n. [L. ladanum, ledanum, Gr. la`danon, lh`danon, fr. lh^don name of a shrub, mastic; cf. Per. ldan, lden. Cf. Laudanum.] A gum resin gathered from certain Oriental species of Cistus. It has a pungent odor and is chiefly used in making plasters, and for fumigation. [Written also labdanum.]