Deadly fevers, the plague, black death, cholera, malaria, smallpox, taught mankind invaluable lessons. Millions of human beings died before the mind of man devoted itself to preventing the diseases for which no sure cure had been found. Efforts to conquer these diseases were tardy because men were taught that some unseen power was punishing men and governments for their sins. The difference between the old and the new way is shown powerfully by a painting in the Liverpool Gallery entitled "The Plague." A mediæval village is strewn with the dead and dying. Bloated, spotted faces look into the eyes of ghouls as laces and jewelry are torn from bodies not yet cold. In the foreground a muscular giant, paragon of conscious virtue, clad like John the Baptist and Bible in hand, finds his way among his plague-stricken fellow-townsmen, urging them to turn from their sins. Modern efficiency learns of the first outbreak of the plague, isolates the patient, kills rats and their fleas which spread the disease, thoroughly cleanses or destroys, if necessary, all infected clothing, bedding, floors, and walls, and makes it possible for us to go on living for each other with a better chance of "bringing forth fruits worthy for repentance."
Where boards of health make it compulsory to report cases of sickness due to contagion, health records are a reliable index to "catching" diseases. But now that the chief infection is the kind that afflicts children, we can read the index before the outbreak that calls in a physician to diagnose the case. School examination shows which children have defects that welcome and encourage disease germs. It points to homes that cultivate germs, and consequently menace other homes. To locate children who have enlarged tonsils may prevent a diphtheria epidemic. To detect in September those who are undernourished, who have bad teeth, and who breathe through the mouth will help forecast winter's outbreaks of scarlet fever and measles. One dollar spent at this season in examination for soil hospitable to disease germs may save fifty dollars otherwise necessary for inspection and cure of contagious diseases.
It is harder at first to interest a community in medical examination than in medical inspection, because we are all afraid of "catching" diseases, while few of us know how they originate and how they can be prevented by correcting the unfavorable conditions which physical examination of school children will bring to light.
Courses in germ sociology are therefore of prime necessity. How do germs act? On what do they live? Why do they move from place to place? What causes them to become extinct? With few exceptions, germs migrate for the same reason as man,—search for food, love of conquest, and love of adventure. When there is plenty of food they multiply rapidly. Full of life, overflowing with vitality, they move out for new worlds to conquer. Like human beings, they will do their best to get away from a country that provides a scanty food supply. Like men and women, they starve if they cannot eat. Like boys and girls, they avoid enemies; the weak give way to the strong, the slow to the swift, the devitalized to the vitalized.
Human sociology imprisons, puts to death, deprives of opportunity to do evil, or reforms those who murder, steal, or slander. Germ sociology teaches us to do the same with injurious germs. We imprison them, we take away their food supply, we kill them outright, or we starve them slowly. They have a peculiar diet, being especially partial to decomposing vegetable and animal matter and to what human beings call dirt. By putting this diet out of their reach we make it impossible for them to propagate their kind. By placing poison within their reach or by forcing it upon them we can successfully eliminate them as enemies. As the president of Mexico restored order "by setting a thief to catch a thief," so modern science is setting germs to kill germs that harm crops and human stock. Of utmost consequence is it that the body's germ consumer—its pretorian guard—be always armed with vitality ready to vanquish every intruding hostile germ. If we are false to our guard, it will turn traitor and join invaders in attacking us. But here, as in dealing with evils that originate with human beings, an ounce of prevention is worth a ton of cure. The most effectual way to eliminate germ diseases is to remove the cause—the food supply of disease germs. The fact that many germs are plants, not animals, does not weaken the analogy, for weeds do not get a chance in well-tilled soil.
Perhaps the most notable recent example of government germ extermination is the triumph over the yellow-fever and malaria mosquito in Panama. When the French started to build a canal in Panama, the first thing they did was to build a hospital. The hospital was always full and the canal was given up. At the time the United States proposed to re-attempt the work, it was thought that it could not be done without great loss of life and without great labor difficulties. Instead of taking the sickness for granted and enlarging the French hospital, the chief medical inspector, Gorgas, took for granted that there need be no unusual sickness if proper preventive measures were taken. He knew what the French had not known, that the yellow-fever scourge depends for its terrors upon mosquitoes. Accordingly, with the aid of six thousand men and five million dollars he set about to starve out the few infected and infectious kinds of mosquito,—the yellow-fever or house mosquito and the malaria or meadow mosquito. He introduced waterworks and hydrants, paved the streets, drained the swamps and pools in which they breed, and instituted a weekly house-to-house inspection to prevent even so much as a pail of stagnant water offering harbor to these enemies. The grass of the meadows where the malaria mosquito breeds was cut short and kept short within three hundred feet of dwellers,—as far as the mosquito can fly. All ditches were disinfected with paraffin, and the natives were forced to observe sanitary laws. President Roosevelt, in his special message to Congress on the Panama Canal in 1906, stated that in the weekly house-to-house visit of the inspectors at the time he was in Panama but two mosquitoes were found. These were not of the dangerous type. As a consequence of this sanitary engineering there is very little sickness in Panama, the hospital is seldom one third full, and the canal is progressing very much faster than was expected. Panama, like Havana, is now safer than many American cities, because cleaner and less hospitable to disease germs.