Not only play, which is the purest expression of motor heredity, but
work and all exercise owe most of whatever pleasure they bring to the
past. The first influence of all right exercise for those in health is
feeling of well-being and exhilaration. This is one chief source of
the strange enthusiasm felt for many special forms of activity, and
the feeling is so strong that it animates many forms of it that are
hygienically unfit. To act vigorously from a full store of energy
gives a reflex of pleasure that is sometimes a passion and may fairly
intoxicate. Animals must move or cease growing and die. While to be
weak is to be miserable, to feel strong is a joy and glory. It gives a
sense of superiority, dignity, endurance, courage, confidence,
enterprise, power, personal validity, virility, and virtue in the
etymological sense of that noble word. To be active, agile, strong, is
especially the glory of young men. Our nature and history have so
disposed our frame that thus all physiological and psychic processes
are stimulated, products of decomposition are washed out by
oxygenation and elimination, the best reaction of all the ganglionic
and sympathetic activities is accused, and vegetative processes are
normalized. Activity may exalt the spirit almost to the point of
ecstasy, and the physical pleasure of it diffuse, irradiate, and
mitigate the sexual stress just at the age when its premature
localization is most deleterious. Just enough at the proper time and
rate contributes to permanent elasticity of mood and disposition,
gives moral self-control, rouses a love of freedom with all that that
great word means, and favors all higher human aspirations.

In all these modes of developing our efferent powers, we conceive that
the race comes very close to the individual youth, and that ancestral
momenta animate motor neurons and muscles and preside over most of the