The overcoat should never be too heavy nor too warm; as a general rule, we should never wear clothes warmer than the temperature at the time requires, always being guided by the thermometer and not by the calendar. It is much better to be clad too lightly than too warmly, for we thus avoid perspiring and thereby catching cold; or, in other words, if clad simply lightly the likelihood of our taking cold is less than when we are too warmly clothed, for then we also perspire less freely. It may be that we shall more readily feel cold, but, fortunately, the sensation of feeling cold does not imply catching cold. In fact, when lightly clad we feel much more inclined to take brisk exercise. Then we feel warm, and, as we shall show in the chapter on exercise, more blood is sent to the periphery of the body and the general nutrition of the skin is increased. Naturally, when we are lightly clad we do not sit about without moving, but we endeavor to create a reaction in the skin by brisk exercise. Englishmen, and especially Scotchmen, rarely wear an overcoat, never sleep in a warmed room, and rarely ever catch cold, which is certainly much more prevalent in countries with overheated houses, as in America, and where the people are more accustomed to ride in the street cars (also heated) than to walk. Catching cold is best obviated by hardening the body against the influence of cold, and this is best done by a continual aëration of the skin, and by means of cold baths, commenced in a judicious manner. We should become accustomed to permit the entrance of air as frequently as possible to the whole surface of the body, which we can do by remaining stark naked in our room for only a few moments several times a day, as already advocated in the chapter on the hygiene of the skin. But still more important is free access to the air, even though cold, if we desire to be immune against colds. Most people who do catch cold contract it first in the head, especially after being in a state of perspiration. The frontal and temporal parts of the head are very well provided with sudorific glands, and it is therefore most unreasonable to prevent free air access by a warm covering. It is also unnecessary, because Nature has already provided these parts with a natural covering, viz.: the hair, which, with the skull, is intended for the adequate protection of our most delicate organ, the special construction of which places us above all other animal creation.