free, whether they know it or not, for good and for evil. And we must do
that in this case, by teaching them sound practical science; the science
of physiology, as applied to health. So, and so only, can we check--I do
not say stop entirely--though I believe even that to be ideally possible;
but at least check the process of degradation which I believe to be
surely going on, not merely in these islands, but in every civilised
country in the world, in proportion to its civilisation.

It is still a question whether science has fully discovered those laws of
hereditary health, the disregard of which causes so many marriages
disastrous to generations yet unborn. But much valuable light has been
thrown on this most mysterious and most important subject during the last
few years. That light--and I thank God for it--is widening and deepening
rapidly. And I doubt not that, in a generation or two more, enough will
be known to be thrown into the shape of practical and proveable rules;
and that, if not a public opinion, yet at least, what is more useful far,
a wide-spread private opinion, will grow up, especially among educated
women, which will prevent many a tragedy and save many a life.

But, as to the laws of personal health: enough, and more than enough, is
known already, to be applied safely and easily by any adults, however
unlearned, to the preservation not only of their own health, but of that
of their children.

The value of healthy habitations, of personal cleanliness, of pure air
and pure water, of various kinds of food, according as each tends to make
bone, fat, or muscle, provided only--provided only--that the food be
unadulterated; the value of various kinds of clothing, and physical
exercise, of a free and equal development of the brain-power, without
undue overstrain in any one direction; in one word, the method of