But it is in rooms either of dwelling or assembling places that the ill effects of infectious dust are most potent, because the air is here not so constantly renewed as it is out-of-doors, and is liable to be breathed over and over again. Dust which gets into houses does not readily leave them, unless special and intelligent means be directed to its removal. We do not usually realize that, though the air itself in inhabited rooms is constantly changing more or less rapidly by diffusion, by draughts, or by purposed ventilation, fine dust particles are not removed under the same influences in proportionate degree. They cling more or less tenaciously to all surfaces on which they have settled, and especially to fabrics, so that currents of abundant force and sufficient distribution to change the air may and usually do leave the lodged dust particles almost entirely undisturbed. One of the most threatening tendencies of modern times in matters of health is that of overcrowding in cities, and the great element of danger from this overcrowding is not only and not chiefly the insufficiency of air in living-rooms and the lack of ready means for its renewal, but the accumulation in this air of infectious germs floating with the dust. Abundant water supply and good sewerage have rendered possible and measurably safe, so far as the ordinary waste of life is concerned, the building of vast tenements which swarm with people. But the means of getting pure air, and especially of disposing of infectious material often floating in it when it is confined, have not at all kept pace with the demands of health and cleanliness. But when we return to larger and more liberally furnished dwellings of the well-to-do classes, we are not reassured, for in some respects the rich are sadly handicapped by the "tyranny of things." Of course, long and thick piled carpets afford persistent lurking-places for infectious as well as other dust. Certainly heavy hangings in a measure hinder the detergent action of the sunlight, shut the used air in and the fresh air out, and shelter floating matter which might otherwise escape. Without doubt, complex upholstery with roughened fabrics increases the difficulties in the maintenance of cleanliness. But the usage of the householder in these matters will, after all, depend upon whether his practical devotion be most at Fashion's or Hygeia's shrine. We may hope for the coming of a time when clean, clear, airy, simply furnished living-rooms shall replace the stuffy, fabric strewn apartments in which the fashionable citizen so much delights to-day.