But the main point lies in the habitual use of the whole of the lungs. Take half a dozen long slow breaths, expanding the lungs to the utmost, and again completely expelling the air, and you will find by experiment that you can hold your breath for very much longer than you could do without such preparation, the reason being that you have in the blood a store of oxygen, however minute, that will carry you on for an additional number of seconds. The advantages of this are obvious in the case of great bodily exertion when the lungs have difficulty in getting enough oxygen to supply the racing heart, for if they can easily, through thorough practice, come without effort into complete use, they will be able to supply without effort a greater fund of oxygen which automatically (and God knows how) they for ever extract from the air, returning the dead air, carbonic acid gas. In other words, the man who can without effort use the whole of his lungs will keep them in a better state of health than one who from continued non-use of the middle and upper parts of them, has not maintained them in similar vigour. Such a man, also, will be far less liable to be attacked by forms of pulmonary disease than one who has half these organs in a state which corresponds to being “below par” as applied to the whole body. Here, as in the case of other muscles, definite exercises are good for increasing the power of the lungs. The following will be found invariably useful:-- * * * * * (1) Breathe slowly in through the nostrils till the whole of the air cavity is expanded to its fullest capacity. (2) Hold the air there from five to ten seconds. (3) Breathe it slowly out till the whole of the air cavity is as far as possible empty. (4) Hold it out for from five to ten seconds. At first this exercise will be found fatiguing to the lungs and the fatigue will be manifested, if not in giddiness, in a tendency to be out of breath. By all means be out of breath, and, when the breathing is normal again, repeat the exercise, going through it half a dozen times. After a week you will find you can repeat it a dozen times or so without intermission, or the desire for intermission. During the breathing in, it will both help the lungs and encourage a greater fulness of breath to raise the arms and shoulders. They should be held in “shrugged” position while the breath is held, be allowed to drop gradually as the breath goes out, and remain utterly relaxed during the fourth part of the exercise. This exercise will be found most beneficial in enlarging the capacity of the lungs and the power of expansion of the chest, which, by the way, is a far more important thing than the actual size of the chest. The exercise may also be used with the following (see Chapter III.):--