MICROÖRGANISMS AND DUST-MOTES OF THE AIR
Bacteria in the Air. --Microörganisms, or microbes, float in the air. They are of the pathogenic, or disease-producing, type, and of the nonpathogenic varieties, such as the molds that produce ferments. The air transports vast unseen armies of such workers. Some of them are enemies; others are benefactors of the human race. The beneficent varieties are active in clearing away the refuse of animal and vegetable life, in fixing fertilizing gases in the soil, in giving flavor to fruits and proper growth to leguminous crops, in transforming the crudest must into the best claret, and the poorest tobacco leaf into the fragrant Havana; in curing cheese and butter and in fermenting beer, and in a multitude of other useful employments. The virulent varieties, if they gain lodgment in suitable human tissues before the sunlight kills them or weakens their virility, disseminate the zymotic diseases.
BACTERIA DECREASE WITH SUNSHINE AND VENTILATION. --Few disease- producing or other bacteria are found in the air of mountains, or in that of the ocean; and there are many less in the air of the open country than in that of the city. At Montsouris observatory the average number of bacteria in a cubic meter of air has been found to be 345, while in the city of Paris, ten miles away, the number was 4,790.
The number is small in well-ventilated city houses that let an abundance of sunlight into their interiors, but is large in crowded tenements.
An elaborate series of observations, by Carnelley, Haldane, and Anderson, on the number of bacteria in the air of houses in the poorest parts of Dundee, Scotland, between the hours of 12.30 A.M. and 4.30 A.M., showed that in one-room tenements, where as many as six persons occupy one bed, there were, on an average, 60 microbes to 1 quart of air; in two-room houses, 46; and in houses of four rooms, and more, only 9. They found an increase in the death rate of those occupying these quarters in direct proportion to the microörganisms in the air; but they called attention to the