Tyndall interested himself in atmospheric germs and dust. His experiments on sterilization by heat led him to the discovery in 1877 of fractional sterilization (Tyndallization). His work on the subject is included in the above book, in which he also described the bactericidal effects of moulds. The researches of Tyndall, even more than those of Pasteur, dealt the final blow to the doctrine of spontaneous generation; they were fundamental for the progress of bacteriology. See No. 1932.