GENERAL BACTERIOLOGY 
21 
did not find any bacteria in infusion which had been 
boiled, but still many investigators clung to the “spon¬ 
taneous generation” until Pasteur did away with it for 
once and all. 
Pasteur showed that filtering air through cotton wool 
resulted in depositing enormous numbers of microorgan¬ 
isms, and when a single shred of such filter was placed 
in a sterile fluid, the latter would soon be teeming with 
bacteria, whereas, if entrance of air into these sterile 
fluids was prevented such fluids would remain sterile. The 
theory of spontaneous generation then received its death 
blow but for one detail—it could not be explained why 
the application of the same degree of heat did not always 
result in complete sterility; this last fact remained un¬ 
explained until 1870, when Cohn brought to light the ex¬ 
istence of bacterial spores and their very high powers of 
resistance to heat. 
Pasteur now turned his attention to the problem of 
fermentation and not only confirmed the earlier opinion 
of Cagniard-Latour and others, but pointed out a number 
of other fermentations, such as those of lactic acid, the 
decomposition of organic matter by putrefaction, etc. 
The dependence of the latter upon living agents suggested 
to the great English surgeon, Lister, the idea that the 
suppuration of infected wounds was a process identical 
with that of putrefaction, and working along the lines in¬ 
dicated by Pasteur’s work, Lister introduced his anti¬ 
septic and aseptic methods and thus achieved immortal 
fame of having rendered possible modern surgery. 
And now we enter upon the era of discoveries of indi¬ 
vidual causative agents of various infectious diseases. 
In 1863, Davaine not only confirmed the earlier obser¬ 
vations of Brauell and Pollender (1855) on the anthrax 
bacillus, but proved that this disease could always be 
