RESPIRATOR, or breath-warmer, is a sin gular instrument invented some years ago for giving warmth to the air drawn into the lungs in breathing, and thereby enabling invalids to whom cold air is injurious to enjoy the benefits of exercise in the open air without injury or inconvenience.
The apparatus usually consists of from eight to twelve frames of sheet-silver or other metal, about three inches and a half long, one inch and a half wide, and part of an inch thick ; the metal of which is pierced away by machinery so as to leave merely a narrow frame containing six vertical bars of nth and five horizontal bars &la of an inch wide. On both sides of each of these frames a layer of wires an inch and a half long and of an inch thick is soldered, care being taken to connect each wire, not only with the top and bottom bars of the frame, but also with each of the five horizontal bars. The wires are laid about part of an inch apart, and are so nume rous that a large respirator of high power con tains 2000 feet of wire, divided into about 12,000 pieces, and soldered to the frames at more than 80,000 distinct points. The frames
or lattices of wire-work are fixed parallel to each other, and kept a short distance apart by small studs of a substance which is a slow conductor of heat, so that the inner layer is always kept, as nearly as possible, at the tem perature of the air expelled from the lungs, and each successive layer diminishes in warmth, till the outer one is nearly as cold as the external air. The curious and philoso phical application of a non-conducting medium between the metallic screens is essential to . .
the perfect action of the instrument, as'svith out it the heat would be equally diffused, and no part of the metal-work could retain more than half the temperature of the breath. By this arrangement the air inhaled, finding each layer of wire warmer than the preceding, is gradually raised, in respirators of the highest power, to the greatest attainable temperature. These instruments are more especially useful in diseases of the lungs.