One is only comfortable in a dry air when it is of a low temperature. When the dry air becomes heated, there is more moisture given off by the mucous membranes, which causes a feeling of dryness and irritation in the nose, throat, and larynx; there may also be a sensation of uneasiness of the chest, and, at the same time, the individual feels chilly. Persons constantly breathing abnormally dry air lower the resisting power of the respiratory mucous membranes and become very susceptible of taking cold. Since the degree of moisture of the air of a house is equally important as its temperature, every room should be furnished with a hygrometer, which should register from 65 to 70 per cent. of moisture. =The Ventilation of Bed-rooms.=—The importance of the proper ventilation of the sleeping-room will be seen from the fact that two-thirds of the oxygen absorbed in the twenty-four hours is absorbed between 6 o’clock in the evening and 6 o’clock in the morning; and on the state of the air of the bed-room will depend greatly the vitality of the individual. During sleep inspiration occupies ten-twelfths of the respiratory period, while at other times it occupies only five-twelfths of that period. In a closed room the oxygen would eventually be consumed, the air become filled with impurities, and the body languish for want of oxygen and incapacity to throw off its impurities. The air of the room should be perfectly fresh on retiring; where it has been used as a sitting-room, it should be thrown wide open and thoroughly ventilated just before going to bed. The temperature of the room should not be above 65° F. In the bed-room at night all the air coming into the room should come from the same side of the room, and the doors opposite should be closed. If the room is small, and the window is at the head or foot of the bed, some provision must be made to screen the bed, and to allow the air to enter the room without falling directly on the sleeper. In the intense heat of summer, especially if the air is saturated with moisture, one sleeps much more comfortably on the side, with the face almost at the edge of the bed; in this way the formation of a stagnant pool of exhaled air about the face is prevented, which would otherwise be rebreathed, and greatly increase the feeling of discomfort and malaise. On retiring at night the clothes worn during the day should be spread out over chairs to become thoroughly ventilated, instead of being hung up in a closed press or closet. From a sanitary point of view, it is essential that every article of clothing worn during the day should be removed at night. Both clothes and body need ventilation. In the morning the clothes should all be taken off the bed, and they, as well as the night-clothes, should be spread out to be aired during the ventilation of the room. The windows are thrown wide open when one goes to breakfast.