“Evidence that disease germs pass through the air from room to room of a house or from a hospital to its immediate surroundings always breaks down when examined critically. It is indeed not rare now to treat cases of different infectious diseases in the same hospital ward. The one place of possible danger is in the immediate vicinity of a person suffering from a disease affecting the air passages, the mouth, throat, or lungs, such as a ‘cold’ or tuberculosis. Such a person may give out the characteristic microbe for a distance of a few feet from his body, not in quiet expiration, for simple expired air is sterile, but attached to droplets that may be expelled in coughing, sneezing, or forcible speaking. In this manner infection may, and probably does, occur, the evidence being perhaps strongest in the case of tuberculosis. But apart from this source there appears to be little danger of contracting an infectious disease from germs that float in the air.” In regard to sewer gas, which still inspires so much dread in the popular mind, Dr. Lee says: “Workmen in sewers are notoriously strong, vigorous, healthy men, with a low death rate among them. The specter of an invisible monster entering our homes surreptitiously from our plumbing pipes and sapping our lives and the lives of our children must be laid aside; we need no longer leave saucers of so-called ‘chlorides’ standing about our floors to neutralize in an impossible manner mysterious effluvia that do not exist; and when we return to our town houses in the autumn we may enter them with no fears that we are risking our lives by coming into a toxic, germ-infected, sewer gas-laden, deadly atmosphere.” Present-day knowledge on the subject of infectious diseases discredits many ideas that once prevailed with regard to the effects of tropical climates on health. The remarkable results accomplished by vigorous sanitary measures in such places as Havana, the Isthmus of Panama and Guayaquil have aroused hopes--perhaps too sanguine--that eventually all parts of the tropics will be made healthful for the white race. In the Canal Zone the death rate of the large population of American men, women, and children is not higher than prevails in many cities of the United States; whereas, a generation ago, when the French were at work on the canal, the “climate” of this region was regarded as one of the most unhealthful in the world. Some authorities go so far as to assert that the deterioration in the general health and efficiency of white people in the tropics, so far as it actually occurs, is due entirely to preventable diseases. It would seem more rational, however, to assume that there are climates both in and out of the tropics which, on account of their heat, humidity, and other purely physical factors, are not so suitable for habitation for any race of humanity as others. How far acclimatization can go toward offsetting the effects of these atmospheric conditions is problematical.