The effects of exercise are particularly apparent in the lungs.

More fresh air is brought to the lungs and the waste products are driven off.
An attainable minimum for the average adult person might well consist of taking simple exercises in his room, and to get out of doors once a day and walk rapidly for at least half an hour.

In addition, it is desirable for any one up to fifty years of age to take some kind of moderately violent exercise at least once a week.
This should be sufficiently strenuous to induce perspiration.

This is important for several reasons.

In the first place, there is an old saying, which happens to be true, "Never let your blood-vessels get stiff." In addition we should call on the tremendous reserve which Nature gives to us, at least once in a while.
[Illustration: "COUNTING OFF" A COMPANY IN THE YALE GYMNASIUM] [Illustration: "HEAD" POSITION.