HORN, in physiology, a tough, flexible, semitransparent substance, intended for the defence or covering of animals. The hollow horns of the ox, goat, fac.: the hoof, the horny claw and nail,'and the scale of certain insects, as the shell of the tortoise, resemble each other in chemi cal characters; but they differ very widely from stag's horn, ivory, &c. Horn is distinguished from bone, in being softened very completely by heat, either naked, or through the medium.of water, so as to be readily bent to any shape, and to adhere to other pieces of horn in the • same state. Horn contains but a small portion of gelatine, and in this it differs from bone, which contains a great deaL Horn consists chiefly of -condens ed albumen, combined with a small and varying ptirtion of gelatine, with a small part of phosphate of lime. The fixed al - kalies readily and totally dissolve horn into a yellowsaponaceous liquor.
Horn and tortoise-shell are applied to mechanical purposes, which require them to be bent and united in various Ways; this is performed by the aid of heat, ap plied either dry, with warmed irons or burning charcoal; or by softening the horn in boiling water, or in a weak so lution of alkali : when thus softened, they will easily adhere. Mr. Aiken gives the, following process for making the horn-ring that surrounds a common ope ra-glass " A flat piece of horn is cut out, of the requisite shape, the ends to be joined are thinned down by a file, the piece is then put into boiling' water till sufficiently Supple, and is then rolled round a warm iron cylinder, and held in that position by a vice, so that the ends over-lap each other : another piece of iron, -heated and grooved, is then laid Upon the seam of the joined ends, and pressed upon the cylinder, and there con fined by an iron wirer and the heat of the two partially melts that portion of the horn, and cements the ends so completely, that no seam or joining can be observed when cold." For the manner
of making horn to imitate tortoise-shell, see Coma.
Hones is also a musical instrument of the wind kind, chiefly used in hunting, to animate the hunters and the dogs, and to call the latter together.
The French horn is bent into a circle, and goes two or three times round, grow ing gradually bigger and wider towards the end, which in some horns is nine or ten inches over.
'Ionics of insects, the slender oblong bodies projected from the heads of those animals, and otherwise called antenna', or feelers. The horns of insects are ex tremely various ; some being forked, others plumose or feathered, cylindrical, tapering, articulated, &c. As to the use of these parts, some have imagined that they served as feelers, lest the creature should run against any thing that might hurt it; and others there are, who think them the organs of hearing. See ENTO