It is a fallacy to think that sufficient exercise can be taken once a week. In order to be efficient exercise must be regular and at relatively short intervals. All exercise should tend toward using all of the muscles of the body. In fatigue a person has lost control over his muscles. The process of getting into condition, therefore, is directed more toward strengthening the nervous system in its control work over the muscles rather than in increasing sheer muscular strength. Pure creative mental work, although requiring no out-put of physical energy, is perhaps the most productive of fatigue. The brain gets more blood during physical activity and waste products are much better removed. 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. GROUP OF ONE HUNDRED, SENIOR CORPS] WATER, WALKING, AND FOOD Water plays a very important part in the life of man, for without it a person can live for only a short time. Its importance is shown by experimental fasts lasting for thirty days where only water was taken, and when we consider that the body is composed of from 60 to 70 per cent, of water and that the amount which it throws off as waste has to be replaced through nutrition, we realize the value of water to life. The average person, therefore, should take from two to four quarts of water a day. [Illustration: RESULT OF SIXTY DAYS' TRAINING IN CARRIAGE. THE TWO MEN IN FRONT WEIGH 265 AND 230 POUNDS RESPECTIVELY] [Illustration: LOOK AND DETERMINATION ON FIRST DAY'S MARCH, DURING WHICH THE MEN CARRIED IRON BARS WEIGHING NINE POUNDS EACH]