Inhalations. - Vapours employed as inhalations act not only on the bronchial tubes but upon the larynx, pharynx, and nostrils. One of the commonest is that of simple hot water. A jug is filled about half-full of boiling water and the head held over it, the steam being kept in by means of a napkin or towel thrown over the head and around the mouth of the jug. This application often gives great, though temporary, relief in nasal, laryngeal, and bronchial catarrh.

Vapour may be medicated by the addition of various substances to it, such as carbolic acid, tincture of benzoin, creasote, or pine oil. But in order to gain the full advantage of the admixture of these substances it is better that the inspired air should not merely play over the surface of the hot water, but be drawn through it, and for this purpose inhalers are employed. In these the air is inspired by means of a mouthpiece fitted with a valve. This valve prevents the air from passing into the mouthpiece, so that during inhalation it is sucked through a tube which dips under the water and passes into the mouth laden with the vapour. During expiration it passes readily through the valve just mentioned.

In cases of bronchitis the patient breathes much more easily when the air of the room is kept warm and moist, and this is effected by means of a bronchitis kettle. This is simply a tin kettle with a spout about three feet long which projects into the room, so that when the kettle is kept boiling briskly a constant current of steam is driven well out into the room. When this cannot be obtained a substitute may be extemporised by rolling a piece of brown paper into a tube, tying a piece of string around it at intervals so as to keep it in shape, and putting it over the spout of an ordinary kettle. In cases of tracheotomy it is usual to keep the air still warmer and moister by hanging sheets around the bed so as to convert it into a kind of tent, and then conveying the steam from a bronchitis kettle into it by means of an india-rubber tube, or keeping up a constant spray by one of Lister's steam spray producers.

The vapour of the drug itself, without admixture with steam, may in some cases be inhaled (see Vapores, p. 533). Oil of eucalyptus or a solution of thymol in alcohol is thus useful as an antiseptic inhalation in gangrene of the lung and bronchiectasis. Terebene is also used in this way in cases of emphysema and chronic bronchitis. The vapour of pyridine in a room is used in asthma.

Smoke. - The attacks of difficulty of breathing which come on in cases of pure spasmodic asthma, in advanced kidney disease, or in emphysema, are frequently much relieved by inhaling the smoke which issues from burning touch-paper or from powdered

II stramonium (vide also p. 260). The touch-paper or stramonium may be simply laid on a plate, or may be placed at the bottom of a cup or jug, and the fumes inhaled. Datura is often used in the form of cigarettes made either from the leaves of the datura stramonium or datura tatula.