graph; boys surpass girls at all ages, and this
differentiation becomes very marked after the age of fourteen,
after which age girls increase in strength and endurance but very
slightly, while after fourteen boys acquire almost exactly half of
the total power in these two features which they acquire in the
first twenty years of life.

13. The development of vital capacity bears a striking resemblance
to that of endurance, the curves representing the two being almost
identical.

Physiological age, according to studies made in New York City, should
be considered in grading, not only for physical culture classes but for
all high school or continuation classes. Dr. C. Ward Crampton,
assistant physical director, while examining boys in the first grade of
the High School of Commerce, noticed a greater variation in physical
advancement than in years. He kept careful watch of the educational
progress and discovered three clear divisions: (1) boys arrived at
puberty,--postpubescent; (2) boys approaching maturity,--pubescent; (3)
boys not yet approaching maturity,--prepubescent.

The work in lower grades they had all passed satisfactorily, but in
high school only the most advanced class did well. Practically none of
the not-yet-maturing boys survived and few of the almost mature. In
other words, the high school course was fitted to only one of the three
classes of boys turned out of the grammar schools. The others succumbed
like hothouse azaleas at Christmas time, forced beyond their season.
Physiological age, not calendar years or grammar school months, should
determine the studies and the companions of children after the tenth
year. Physiological strength and vitality, not ability to spell or to
remember dates, should be the basis of grading for play and study and
companionship among younger children. Vitality, power to endure
physically, should be the test of work and recreation for adults.
Physicians may be so trained to follow directions issued by experts
that physical examinations will disclose the chief enemies of vitality
and the approximate limits of endurance.

Teachers may train themselves to recognize signs of fatigue in school
children and to adapt each day's, each hour's work to the endurance of
each pupil. One woman principal has written:

School programmes, after they have been based upon the laws of a
child's development, should provide for frequent change of
subject, alternating studi