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January 23, 1943


JAMA. 1943;121(4):261-262. doi:10.1001/jama.1943.02840040037012

Working at Harvard University, William F. and Mildred W. Wells1 invented an apparatus and developed a technic which made it possible to explore the air for micro-organisms in controlled atmospheres. Liquid suspensions of micro-organisms could be atomized into a tank and their presence demonstrated quantitatively by the air centrifuge. These researches established that transmission of infection through the air may take one of two forms, depending on the size of the infected droplet. The more obvious form recognized by Flügge is droplet infection proper. It applies to droplets larger than 0.1 mm. in diameter, which are rapidly removed from the air by gravity before they can dry and within a short distance from the source. The second form may be called air borne infection and deals with the dried residue of infected droplets or droplet nuclei, derived directly from droplets less than 0.1 mm., depending primarily on air for