HEALTH EXERCISES 443
The Germans have long had the right idea, making a feature of systematic training. Remember that symmetry of development is desired not only for the sake of symmetry itself, but because it means a more perfect and well-balanced condition, and usually greater bodily efficiency.
For all around convenience, we may consider that the years between thirteen or fourteen and sixteen form the period of puberty, strictly speaking. During this time the young people are still boys and girls, but in the active process of passing from boyhood and girlhood into manhood and womanhood. From this time on, or from seventeen to twenty-one, we may regard, for convenience, as a secondary stage, in which they are really young men and women, although they are still undergoing the processes of growth and development. We will therefore consider them in reference to these two periods of their development. It is true that they continue to grow and mature for a number of years after the age of twenty-one, especially so in the case of the young men, but yet they are really men and women then and capable of enduring much in the way of physical strain and heavy training, if desired, that it would be unwise for them to attempt during their teens.
Growth in Stature
Growth is very active during both the periods that I have indicated, though far more so in the case of girls during the first period, and more rapid in the case of boys during the second period. Between the ages of thirteen and fifteen or sixteen years the girls grow so fast, by comparison, that they are actually larger and heavier on the average than the boys, the only period in their lives in which they have superiority in this respect. But from sixteen on to twenty-one years the development of the girls is no longer so rapid, while the young men continue to grow at a remarkable rate. And yet this growth in either sex is far more rapid in some cases than in others. One, for instance, may rapidly shoot up to his ultimate height and after that very slowly fill out. And in another case the growth in stature is slower, accompanied by the