394 CLINICAL BACTERIOLOGY. 



rainfall and during the winter the number of germs in the 

 air is considerably diminished. In the still air of rooms 

 comparatively few germs are found, even in densely occu- 

 pied quarters as, for instance, in hospital-wards. As 

 soon, however, as dust is set in motion, the number of 

 microorganisms in the air increases enormously to as 

 many as 16,000 in the cubic meter. The majority of the 

 bacteria, however, by reason of their weight, are soon 

 again, after from half an hour to an hour, deposited upon 

 the floor and the walls with the dust, and the air will then 

 contain almost only the light mold-spores. 



Sources of Aerial Germs (Air-infection). The pres- 

 ence of spores of molds in the air in such large number is 

 explained by the fact that generally the fruit-bearers of the 

 fungous deposits project upward from the mycelium, and 

 the spores can, therefore, be readily conveyed by currents 

 of air. 



Bacteria frequently find their way into the air with the 

 small fibers separated from clothing, handkerchiefs, linen, 

 etc. 



With regard to the possibility of air-infection, recent in- 

 vestigations by Fliigge and his pupils have yielded a wealth 

 of facts that are well adapted to modify the views hitherto 

 held. The earlier supposition that no germs enter the air 

 from liquids or from moist surfaces is, according to Fliigge, 

 valid only in so far as the surface of the fluid remains un- 

 moved and intact. A moderate wind (a velocity of four 

 meters in a second) suffices, however, to set free germ- 

 containing small drops from water-surfaces, moist articles, 

 and the like. The conditions favoring the conversion of 

 fluids into small drops in the air are often present, as in the 

 open air, in a high degree in the neighborhood of the 

 surging sea, of water-mills, etc., in lesser degree with every 

 current of air that sets the leaves of trees in motion. In 

 closed apartments, according to ' Fliigge, small drops that 

 enter the air are set free more frequently than is generally 

 believed in sprinkling, in washing, in manipulating wet 

 linen, and upon which especial weight must be placed 

 in speaking, sneezing, and coughing. These droplets, 

 whether they contain germs or not, are, as Fliigge further 

 demonstrated, carried away by the slightest currents of air 

 for considerable distances, and not only in a horizontal, but 

 also in a vertical direction. In order to demonstrate the 



