"After being in such a situation many people find themselves affected by that _febricula_, which the English alone call a _cold_, and, perhaps, from that name, imagine they have caught the malady by _going out_ of the room, when it was, in fact, by being in it." Now, to show that his hopes have not yet been fully realized, although one century has nearly closed since he wrote what I have just read, and this unnecessary and unfortunate prejudice against night air still prevails extensively, I will read a few lines from the highest public medical authority in this city. It is the instructions of the Board of Health for the prevention of cholera for 1866: ARTICLE--"VENTILATION." "Your premises, particularly sleeping apartments and cellars, should be thoroughly ventilated. Ventilation is no less a purifier than water. "It cleanses by oxidizing and drying. Keep your houses open and your windows hoisted during the day in good weather, and from ten o'clock until four in the afternoon, that they may have the full benefit of sunlight and free circulation of pure air. _During the remaining hours of the day, and through the night, keep the windows closed._ When the weather is cool or rainy, be sure to keep a fire in the house, in order to prevent dampness, or in sparsely settled neighborhoods, or in the suburbs of the city, have a fire in the house the entire season." On page 9 we read: "Be careful to dress comfortably for the season, _avoid the night air_ as much as possible, and when thus exposed, put on an extra garment and do not go into _the night air_ when in a state of perspiration." Thus, while recognizing the great value and importance of ventilation in a general way, they give the most definite instructions for thoroughly and most effectually preventing it, because it is at night, especially when we are asleep and _cannot move from the air, that the air ought to be moved from us_. The frequent recommendations to avoid "night air" are simply recommendations to smother ourselves to death, because the foul, poisonous exhalations from our lungs cannot be removed from our chambers without being replaced by night air; there is no other fresh air at night but night air. The recommendation to build a fire in the house on cool days, and in low marshy districts every day in the year, is an excellent one. The recommendations to dress warmly and to avoid checking a perspiration suddenly, are valuable suggestions and too much attention cannot be paid to them. But they are of equally great importance in reference to day air as to night air. To shelter oneself from the sudden change of temperature after sundown is an animal instinct, and a very necessary one, which is strongly implanted in man and beast alike.