RESPIRATOR is the name given by its inventor, Mr. Jeffreys, to an instrument which gives warmth to the air draWn into the lungs in breathing. It is attached to the mouth, and is composed of several layers of very tine wire, fixed so near together that the exhaled air passing through them is diffused over a very large amount of surface, its warmth being absorbed by the metal, which, being an excellent conductor of heat, freely returns it to the cold air, drziwn in through it in the act of inspiration. Mr. Jeffreys considers it necessary that about 20 layers of metal-work should be used, and in order to make the instrument as light and compact its possible, eaehlayer must be extremely thin. The apparatus usually consists of from to 12 frames of sheet-silver or other metal, about 31 in. long, 11 in. wide, and of an in. thick, the metal of which is pierced away by machinery so as to leave only a narrow framework, consisting of 6 vertical bars of an in. wide, and 5 horizontal bars, with a width of of an in. thick. To each side of each of these frames is soldered a layer of wires 11 in. long, and thth of an in. thick. These wires are laid at of an in. apart, and are so numerous that a large respirator of high power contains 2,000 ft. of wire, divided into about 12,000pieces, and soldered to the frames at more than 80,000 points. The frames, of wire-work, are fixed parallel tb each other, and kept a small distance apart by small knots of a bad con ductor of heat, so that the inner layers is alway kept at almost the temperature of tire expired air, and each successive layer diminishes in warmth, till the outer one is nearly as cold as the external air. By this arrangement, the air that is inhaled meeting with
layers of wire of gradually increasing heat, is raised in the most powerful respirators to the highest attainable temperature. Such respirators have 24 layers of wire-work, those of medium power 16, and the weakest 8. The.whole of the wire-work is curved, so as to tit closely to the face, and is ineldsed in a border or case of soft leather; and an miter coat, usually of a very fine and open woolen fabric, is added. The form of instrument chiefly used is fixed 'over the mouth, and is named the oral respirator. For an instru ment to cover both the mouth and nostrils, the term ori-nasal respirator is used. As defective and imperfect imitations of Mr. Jeffreys's respirator have been advertised, the original inventor has supe•added the word pneamoclime, or "climate for the lungs," to all the respirators for which he holds himself responsible. The use of these instruments in allowing persons with delicate lungs to take out-of-door exercise vrith safety and advantage in comparatively severe weather, is now universally recognized by the medi cal profession.