the more imperative is the demand for fuel."[12] These
statements justify and explain the instinctive demand for sleep. They
also show why it is that infants require more sleep than children, and
children than middle-age folk, and middle-age folk than old people.
Infants must have sleep for repair and rapid growth; children, for
repair and moderate growth; middle-age folk, for repair without
growth; and old people, only for the minimum of repair. Girls, between
the ages of fourteen and eighteen, must have sleep, not only for
repair and growth, like boys, but for the additional task of
constructing, or, more properly speaking, of developing and perfecting
then, a reproductive system,--the engine within an engine. The bearing
of this physiological fact upon education is obvious. Work of the
school is work of the brain. Work of the brain eats the brain away.
Sleep is the chance and laboratory of repair. If a child's brain-work
and sleep are normally proportioned to each other, each night will
more than make good each day's loss. Clear heads will greet each
welcome morn. But if the reverse occurs, the night will not repair the
day; and aching heads will signalize the advance of neuralgia,
tubercle, and disease. So Nature punishes disobedience.

It is apparent, from these physiological considerations, that, in
order to give girls a fair chance in education, four conditions at
least must be observed: first, a sufficient supply of appropriate
nutriment; secondly, a normal management of the catamenial functions,
including the building of the reproductive apparatus; thirdly, mental
and physical work so apportioned, that repair shall exceed waste, and
a margin be left for general and sexual development; and fourthly,
sufficient sleep. Evidence of the results brought about by a disregard
of these conditions will next be given.

FOOTNOTES:

[3] Human Physiology, p. 546.

[4] As might be expected, the mortality of girls is greater at this
period than that of boys, an additional reason for imposing less labor
on the former at that time. According to the authority of MM. Quetelet
and Smits, the mortality of the two sexes is equal in childhood, or
that of the male is greatest; but that of the female rises between the
ages of fourteen and sixteen to 1.28 to one male death. For the next
four years, it falls again to 1.05 females to one male death.--_Sur la
Reproduction et la Mortalite de l'Homme. 8vo. Bruxelles._

[5] Lectures on D