lives when
they had stronger sexual interests, and some are peculiar to people of
their readjusted glandular activity. Their reproductive contribution to
society has been made.

Pre-pubertal childhood and youth, on the contrary, has its biological
contributions to society still before it. The glandular activity of boys
and girls is perhaps not so unlike as to justify society in giving them
a different kind of education and preparation for group life. The excuse
for two sorts of training is that the two sexes will not do the same
work after puberty. Hence the question of youthful training is
sociological almost entirely--not biological--or rather, it rests upon
the biology, not of childhood but of the reproductive period, which
society anticipates.

Instead of scattering attention over the whole history of the universe,
then, or even over the general field of biology, in dealing with sex as
a social problem, the emphasis must be upon the human life cycle during
the functional-reproductive period. Other biological data than that
which concerns this period is merely introductory or explanatory. The
extent to which the sociological problem involved is linked up with
general biological considerations like natural selection, adaptation and
specialization will be summarized in a separate chapter.

Earlier female maturity and puberty, as well as lighter structure, have
already been accounted for by the metabolism, especially of the calcium
salts. These have also been shown to be the key fact in the monthly
periodicity of the mammalian female. Nearly all of the anatomical and
physiological sex differences catalogued by such pioneer workers as
Ellis, Ploss, Thomas and Bucura are simply what we should expect from
the less active and in some ways peculiar metabolism of woman.

Among such differences are the size and shape of bones and other body
structures, the more plentiful haemoglobin in male blood during the
reproductive period, and such blood peculiarities as the production of
more carbonic acid or the higher specific gravity in the male. The
greater percentage of fat as compared with muscle in women[19], if it is
generally true, is what we should expect from a lower metabolism and a
tendency to store materials. The long list of diseases which are more or
less sex-limited [20; 14, pp.160f.; 18] are largely endocrine. Even those
which do not primarily concern the internal secretory system would be
expected to work somewhat