lowly-nourished brain of a lymphatic man,
frequently evolves much less intellectual force than does the smaller,
perhaps more compact, brain of another, in whom the circulation is more
active, and the nutrition probably more elaborate.

These facts, and many others that might be quoted, are pertinent to our
subject, on account of the influence exercised over the ganglionic
centres by the development and functional activity of those of thought.
Stimulation of the cerebral hemispheres is one of the most powerful
means of counteracting paralysis of the vaso-motor centre, with all its
consequences. Habitual activity of these centres--implying,
psychologically, habitual activity of thought, physiologically, a more
active local circulation--is therefore the best method at our disposal
for permanently counteracting tendencies to irregular action in this
centre, in the emotional ganglia lying in its vicinity, and in the
vaso-motor nerves dependent upon it.

A method of such general supervision does not in itself forbid the
co-education of girls and boys; for from this more general point of
view, the health of the latter during adolescence really requires
precisely the same precautions as that of the former. Attention is less
frequently drawn to the precautions required in the case of boys, mainly
because such precautions are more frequently observed in regard to them.
But besides, girls arrive at the period of adolescence already enervated
by the senseless training of their childhood, on which distinctions of
sex have been obtruded long before they are established by nature.
Finally, since peculiarities relating to the sexual organs are
inherited, if at all, from the parent of the same sex,[48] the germs of
uterine diseases acquired by mothers too frequently exist in daughters,
ready to be developed at the earliest opportunity.

As a matter of fact, therefore, the existing generation of girls,
especially in New England, too often possess a delicacy of organization
greater than that of their brothers, and demanding a special supervision
and watchfulness, best bestowed when they are educated apart. For the
reasons already detailed at length, we think that such supervision does
not necessitate periodical intermittence of study, except in special
cases, that constitute a decided minority among the whole. It does
necessitate, however, the more difficult task of providing for adequate
rest and exercise during every day of the month