Dr. Angus Smith's air test, if it could be made of simpler application, would be invaluable to use in every sleeping and sick room. Just as without the use of a thermometer no nurse should ever put a patient into a bath, so should no nurse, or mother, or superintendent be without the air test in any ward, nursery, or sleeping-room. If the main function of a nurse is to maintain the air within the room as fresh as the air without, without lowering the temperature, then she should always be provided with a thermometer which indicates the temperature, with an air test which indicates the organic matter of the air. But to be used, the latter must be made as simple a little instrument as the former, and both should be self-registering. The senses of nurses and mothers become so dulled to foul air that they are perfectly unconscious of what an atmosphere they have let their children, patients, or charges, sleep in. But if the tell-tale air-test were to exhibit in the morning, both to nurses and patients and to the superior officer going round, what the atmosphere has been during the night, I question if any greater security could be afforded against a recurrence of the misdemeanour. And oh; the crowded national school! where so many children's epidemics have their origin, what a tale its air-test would tell! We should have parents saying, and saying rightly, "I will not send my child to that school, the air-test stands at 'Horrid.'" And the dormitories of our great boarding schools! Scarlet fever would be no more ascribed to contagion, but to its right cause, the air-test standing at "Foul." We should hear no longer of "Mysterious Dispensations," and of "Plague and Pestilence," being "in God's hands," when, so far as we know, He has put them into our own. The little air-test would both betray the cause of these "mysterious pestilences," and call upon us to remedy it. [5] With private sick, I think, but certainly with hospital sick, the nurse should never be satisfied as to the freshness of their atmosphere, unless she can feel the air gently moving over her face, when still. But it is often observed that nurses who make the greatest outcry against open windows are those who take the least pains to prevent dangerous draughts. The door of the patients' room or ward _must_ sometimes stand open to allow of persons passing in and out, or heavy things being carried in and out. The careful nurse will keep the door shut while she shuts the windows, and then, and not before, set the door open, so that a patient may not be left sitting up in bed, perhaps in a profuse perspiration, directly in the draught between the open door and window. Neither, of course, should a patient, while being washed or in any way exposed, remain in the draught of an open window or door. [6] [Sidenote: Don't make your sick-room into a sewer.]