Adolescence is a new birth, for the higher and more completely human
traits are now born. The qualities of body and soul that now emerge
are far newer. The child comes from and harks back to a remoter past;
the adolescent is neo-atavistic, and in him the later acquisitions of
the race slowly become prepotent. Development is less gradual and more
saltatory, suggestive of some ancient period of storm and stress when
old moorings were broken and a higher level attained. The annual rate
of growth in height, weight, and strength is increased and often
doubled, and even more. Important functions, previously non-existent,
arise. Growth of parts and organs loses its former proportions, some
permanently and some for a season. Some of these are still growing in
old age and others are soon arrested and atrophy. The old measures of
dimensions become obsolete, and old harmonies are broken. The range of
individual differences and average errors in all physical measurements
and all psychic tests increases. Some linger long in the childish
stage and advance late or slowly, while others push on with a sudden
outburst of impulsion to early maturity. Bones and muscles lead all
other tissues, as if they vied with each other; and there is frequent
flabbiness or tension as one or the other leads. Nature arms youth for
conflict with all the resources at her command--speed, power of
shoulder, biceps, back, leg, jaw--strengthens and enlarges skull,
thorax, hips, makes man aggressive and prepares woman's frame for
maternity.

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