To sum up: while the earlier steps of civilization unquestionably provide that environment which is necessary for the development of tuberculosis, the later stages, with their greatly increased power over the forces of nature, their higher intelligence and their broader humanity, not merely have it in their power to destroy it, but are already well on the way to do so. CHAPTER VIII THE GREAT SCOURGE Not only have most diseases a living cause, and a consequent natural history and course, but they have a special method of attack, which looks almost like a preference. It seems little wonder that the terror-stricken imagination of our Stone Age ancestors should have personified them as demons, "attacking" or leaping upon their victims and "seizing" them with malevolent delight. The concrete comparison was ready to their hand in the attack of fierce beasts of prey; and as the tiger leaps for the head to break the neck with one stroke of his paw, the wildcat flies at the face, the wolf springs for the slack of the flank or the hamstring, so these different disease demons appear each to have its favorite point of attack: smallpox, the skin; cholera, the bowels; the Black Death, the armpits and the groin; and pneumonia, the lung. There are probably few diseases which are so clearly recognized by every one and about which popular impressions are in the main so clear-cut and so correct as pneumonia. The stabbing pain in the chest, the cough, the rusty or blood-stained expectoration, the rapid breathing, all stamp it unmistakably as a disease of the lung. Its furious onset with a teeth-chattering chill, followed by a high fever and flushed face, and its rapid course toward recovery or death, mark it off sharply from all other lung infections. Its popular names of "lung fever," "lung plague," "congestion of the lungs," are as graphic and distinctive as anything that medical science has invented. In fact, our most universally accepted term for it, pneumonia, is merely the Greek equivalent of the first of these.