Stand erect with the arms outstretched and hands together in front of the face. Bring the arms quickly and suddenly back until they are level with the shoulders, still at full stretch, at the same time letting the breath come suddenly and fully into the lungs. After a pause of a second or two, with the chest inflated to its utmost, bring the arms back to the original position, expelling all the breath with the same suddenness. These two exercises, it must be repeated, are (especially for those who need them--_i.e._, those who have not been in the habit of using the whole of the lungs) rather trying, particularly at first; on no account, therefore, strain or exhaust yourself over them. Let the facility in doing them come slowly. These, like all lung exercise, should be performed by an open window or in a room with good ventilation and as free as possible from dust, since the point is to charge the lungs thoroughly with air, which had therefore better be pure air. The open mouth may be used in these exercises, since a full draught of air has to be taken in suddenly. But apart from actual exercises for the lungs, an even more important point is that these organs should as far as possible be given, night and day alike, a proper supply of air for their normal and automatic working; and their one and constant demand is oxygen. Considering how much there is in existence, it is wonderful how rare civilised life has contrived to make it, while builders and architects seem to adopt the uncompromising attitude of saying, “We will give you air and draughts, or no air and no draughts.” Sometimes even, by an excess of diabolical humour, they manage to give one draughts and no air, and render rooms both cold and stuffy; and the continual breathing of unvivified air, of air which has been exhausted of its oxygen by the breathing of other people and not renewed by a constant fresh supply coming in, is probably responsible for as much languor and indisposition as any of the errors of diet mentioned in the previous chapter. Nor is it the least necessary that because a room is hot the air should be bad; indeed, one of the reasons why a good fire in the room is healthy is that, if there is an adequate ventilator, the fire by its burning and by the passage of the heat up the chimney induces a current of air, and though it warms a room and may make it even over-hot, yet that heated air is not nearly so enervating as the air of a cooler and ill-ventilated room. The lungs do not in the least object to be fed with even roasted air, as in a Turkish bath, any more than they dislike air of the utmost extremity of cold; what they do rebel against is being given vitiated and exhausted air. It is the quality rather than the temperature of the air we breathe which has to be considered, and many people who say they cannot stand a hot room mean not really a hot room but a stuffy one.