terrors of the Black Plagues, the devastation, greater and more
frightful than war, which centuries ago swept over Europe and Asia time
and again, scarcely leaving enough of the living to bury the dead.
Cholera, smallpox, bubonic plague, with terrifying suddenness fell upon
a world of ignorance, and each in turn humbled humanity to the dust
before its invisible enemies. Even within our own recollection, the
germ of influenza, gaining a foothold inside our defenses, took the
world by storm, and beginning probably at Hongkong, within the years
1889-90, swept the entire habitable earth, affecting hundreds of
thousands of human beings, and leaving a long train of debilitating and
even crippling complications.

Here and there through the various silent battles between human beings
and bacteria there stand out heroic figures, men whose powers of mind
and gifts of insight and observation have made them the generals in our
fight against the armies of disease. But their gifts would have been
wasted had they lacked the one essential aid without which leadership is
futile. This is the force of enlightened public opinion, the backing of
the every-day man. It is the coöperation of every-day men, acting on the
organized knowledge of leaders, which has made possible the virtual
extinction of the ancient scourges of smallpox, cholera, and bubonic
plague.

Just as certain diseases are gradually passing into history through
human effort, and the time is already in sight when malaria and yellow
fever, the latest objects of attack, will disappear before the campaign
of preventive medicine, so there are diseases, some of them ancient,
others of more recent recognition, which are gradually being brought
into the light of public understanding. Conspicuous among them is a
group of three, which, in contrast to the spectacular course of great