Letter from Howard Walter Florey to C H Andrews, National Institute for Medical Research, Hampstead Says that two American workers have found that the typhus rickettsia is affected by the injection of penicillin into the eggs in which the organism is developing - would Andrewes repeat the experiments - gives details and discusses possibilities arising should the rickettsia be sensitive - comments on evidence found at Mayo Clinic that the psittacosis virus is affected by penicillin. 29 April 1944