The struggle of man against his unseen and silent enemies, the lower or bacterial forms of life, once one becomes alive to it, has an irresistible fascination. More dramatic than any novel, more sombre and terrifying than a battle fought in the dark, would be the intimate picture of the battle of our bodies against the hosts of disease. If we could see with the eye of the microscope and feel and hear with the delicacy of chemical and physical interactions between atoms, the heat and intensity and the savage relentlessness of that battle would blot out all perception of anything but itself. Just as there are sounds we cannot hear, and light we cannot see, so there is a world of small things, living in us and around us, which sways our destiny and carries astray the best laid schemes of our wills and personalities. The gradual development of an awareness, a realization of the power of this world of minute things, has been the index of progress in the bodily well-being of the human race through the centuries marking the rebirth of medicine after the sleep of the Dark Ages.

In these days of sanitary measures and successful public health activity, it is becoming more and more difficult for us to realize the 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 epidemics, pursue their work of destruction quietly, slowly undermining, in their long-drawn course, the very foundations of human life. Tuberculosis, or consumption, now the best known of the three, may perhaps be called the first of these great plagues, not because it is the oldest or the most wide-spread necessarily, but because it has been the longest known and most widely understood by the world at large. Cancer, still of unknown cause, is the second great modern plague. The third great plague is syphilis, a disease which, in these times of public enlightenment, is still shrouded in obscurity, entrenched behind a barrier of silence, and armed, by our own ignorance and false shame, with a thousand times its actual power to destroy..