National Customs.--There is a curious difference in the attitude of mind of the various nations towards exercise. Most of the southern nations of Europe do not as a rule take any violent exercise. As is well known, however, they are not for this reason any less healthy than their northern contemporaries, though perhaps they are less strong and muscular. But muscularity and health are not convertible terms, though many people seem to think they are. An excess of any tissue is not good. Our economy should be taxed to maintain only what is useful to it. Nature evidently intended, in cold climates at least, that men should maintain a certain blanket of fat to help them retain their natural heat, but any excess of fat lessens their resistive vitality by lowering oxidation processes. Fat in cold climates can be used to advantage as a retainer of heat. In the warmer climate it would be a decided disadvantage. Muscular tissue is a manufacturer of heat and this is a decided advantage in the colder climates, but in the temperate zone, where the summers are very warm, muscle in over-abundance, unless its energy is consumed by actual physical exercise, may be quite as much of a burden as fat. Muscular people do not stand heat well. They demand exercise to keep muscle energy from being converted into heat, and they require frequent cold baths, and other forms of heat dissipation, in order to be reasonably comfortable. Exercise in Early Years.--The question of the amount of exercise that is to be taken must be decided at an early age for individuals. Most of the young people of the Celtic and Anglo-Saxon races are tempted by traditions and by social usage to develop considerable muscle during their growing years. In this respect, the difference between the German and the English schoolboy is very striking. The English schoolboy is likely to be as "hard as nails," as the expression is, as a consequence of violent exercise in his various sports, taken often to the uttermost limit of fatigue. The German schoolboy has his walk to and from school, and some other simple methodical exercises, with some mild amusements that make little demand on muscle, but of games in the open he has very few, and of the violent sports he has none at all. A comparison of the health of the two nations will not show that the English boy, who receives a public school and a university education, with all their temptations to exercise, enjoys any better health, and, above all, reaches an average longer life than the German youth, who has gone through a similar educational career in his own country, but without the athletic training that the English schoolboy has had.