But a little time each day is needed, never over half an hour of actual work in-doors and an hour out-of-doors. Suppose a teacher has forty pupils, and that thirty of them have either weak or indifferent chests. Let her form a chest-class out of the thirty, and, for ten minutes a day, let them practice exercises aimed exclusively to enlarge and develop the chest. Some of such exercises will be pointed out on page 245. Begin very gradually, so mildly that the weakest chest there shall have no ache or pain from the exercise. For the first week do that same work, and that much of it daily, and no more; but do it carefully, and do not miss a stroke. Let this exercise come at the appointed hour, as certainly as any other study. The second week make the work a trifle harder, or longer, or both. In this, and in every exercise, insist, as far as possible, on an erect carriage of the head and neck, and frequently point out their value. Insist, further, on the pupil's always inhaling as large, and full, and slow breaths as he can, seeing to it that every air-cell is brought into vigorous play. Be careful that he or she does not, without your knowledge, get hold of heavier apparatus, or try more difficult exercise in the same direction, before the muscles are trained to take it. Overdoing is not only useless, and sure to bring stiffness and aches, but it is in it that any danger lies, never in light and simple work, adapted to the pupil's present strength, and done under the teacher's eye, or in heavier work after he has been trained gradually up to it. Now, when a fortnight has gone by, use a little heavier weights; stay at the work without weights a little longer, or draw the pulley-weight a few more strokes daily, never forgetting to hold the head and neck erect.