We shall take it for granted that the reader does not require to have proven to him the so-called “germ theory” of disease. The phrase, which was once accurate, is now misleading, for the germ “theory” is part of the definite achievement of science. Not only have we succeeded in isolating the specific germ whose introduction into the body is responsible for different diseases, but in many cases, by studying the history and behavior of the germ, we have been able to find methods of checking its inroads, and so have delivered men from scourges like yellow fever and the bubonic plague. THE DEFENSES OF THE BODY An experiment that is often tried in operating rooms furnishes a vivid illustration of the omnipresence of these invisible, yet potent, foes of life. In order to impress upon young surgeons the importance of maintaining antiseptic conditions, they are instructed to thoroughly wash their hands and arms in antiseptic soap and water; then they are told to leave their arms exposed for a few minutes, after which a microscopic examination of the bared skin will result in exposing the presence of myriads of germs. Many of these are, of course, harmless; some are even “friendly”—since they make war upon the dangerous kinds. But others are the deadly organisms which find lodgment in the lungs and cause pneumonia and tuberculosis; or the thirty odd varieties of bacilli which cause the various kinds of grippe and influenza and “colds,” which plague the civilized man; or others which, finding entrance into the digestive tract, are the cause of typhoid and other deadly fevers. So it appears that we live within our bodies somewhat in the same fashion as isolated barons lived in their castles in the Dark Ages, beleaguered constantly by hordes of enemies that are bent upon our destruction—these being billions upon billions of disease germs. Every portion of the body has its defenses to protect it against these swarms. The skin is germ-tight in health; and each of the gateways to the interior of the body has its own peculiar guard—tears, wax, mucous membrane, etc. As Dr. Edward A. Ayers points out,—“Many of these entrances are lined with out-sweeping brooms—fine hairs similar to the ‘nap’ or ‘pile’ of carpet or plush—which constantly sweep back and forth like wheat stalks waving in the breeze. You cannot see them with the low-powered eye, but neither can you see the germs. They sweep the mucous from lungs and throat, and try to keep the ventilators free from dust and germs. Behind the scurf wall and the broom brigade of the mucous membranes, the soldier corpuscles of the blood march around the entire fortress every twenty-eight seconds” (the time occupied by the blood in its circulation through the body). HEALTHY BODIES ARE GERM-PROOF