To use such an inhaler, the glass vial is first detached from the rubber tube, and the chosen dose of drug squirted into it. A child of five or six will require 3 c.c., an adult up to 5 c.c.; this dose should never be exceeded. The vial is then rapidly reconnected with the inhaler. The face-piece is adapted to the face, care being first taken to place between the teeth a mouth prop or a gag. This enables one to get immediate access to the mouth when the inhaler is removed. The patient is then told to breathe deeply once or twice. During the inspiration the mask is lifted slightly, and the ensuing expiration is then caught in the bag by pressing down the mask on to the face. To volatilise the drug there are two alternative methods. In the one, part or the whole of the dose is tipped into the rubber bag by elevating the vial. A far better is the “Vapour” method, almost universally used in Edinburgh owing to the advocacy of Dr Logan Turner. A tumbler is filled with hot water, and the bottom of the glass vial is allowed first to touch, and after a few seconds to be immersed in it. Some thirty to forty seconds suffice to vapourise the whole of the dose. Ethyl chloride given by itself should always be administered to a patient in the recumbent position. A dose sufficient to produce anæsthesia without the aid of nitrous oxide or ether will not be safe in the erect posture. The case is quite different where a small dose only is given, to assist the action of nitrous oxide, or facilitate the induction stage of ether. Signs of Anæsthesia. Ethyl chloride is very rapid in its action, some sixty seconds availing to produce quite a deep anæsthesia. _Respiration_ is at first deepened and quickened: as full anæsthesia is attained it remains rather deeper than normal, and is accompanied usually by light snoring. The colour should remain perfectly good: the pupils show marked dilatation, the corneal reflex is abolished, and good muscular relaxation is attained. With no anæsthetic is it so essential as with this, to become acquainted with the type of respiration normally to be expected, and to watch for any departure therefrom with cat-like vigilance. The other danger signal is the pupil. It should be dilated, but a rim of iris should still be perceptible. Once anæsthesia is established, the inhaler should be removed, and the surgeon may begin his work. He will have for its completion some 80–90 seconds against the 40–50 available after nitrous oxide. With ethyl chloride there is a somewhat prolonged “analgesic” stage. The patient is partly conscious and may even be phonating, but seems unconscious of the infliction of pain unless very severe measures are being used. The Scope of Ethyl Chloride.