In 1942 Hirst1 of the International Health Division, Rockefeller Foundation, developed a method for the isolation of human influenza virus by direct inoculation of mouth washings into 13 day old chick embryos. The mouth washings were first passed through a collodion membrane so as to remove bacterial contaminations. Hirst found that so much of the virus is lost by collodion filtration as often to render the filtrate noninfectious. Rose and his associates2 of Columbia University therefore tried to render filtration unnecessary by the use of chemical antiseptics. Preliminary experiments showed that most of the available antiseptics when used in concentrations that would prevent bacterial growth were either lethal for the chick embryo or would interfere with the development of the accompanying virus.
In order to find a more favorable antibiotic, Rose tested the bactericidal or bacteriostatic effects of penicillin when added to sputum. Fifty-five specimens of sputum from