HISTORICAL. 5 
air passed through such a filter does not cause the fermentation of 
boiled organic liquids. 
The experiments of Pasteur and of Hoffman, made a few years 
later, showed that even without a cotton filter, when the neck of the 
flask containing the boiled liquid is long drawn out and turned down- 
ward, the contents may be preserved indefinitely without change. 
In this case suspended particles do not reach the interior of the flask, 
as there is no current of air to carry them upward through its long- 
drawn-out neck, and they are prevented by the force of gravity from 
ascending. 
Tyndall showed at a later date that in a closed chamber, in which 
the air is not disturbed by currents, all suspended particles settle to 
the floor of the chamber, leaving the air optically pure, as is proved 
by passing a beam of light through such a chamber. 
Notwithstanding the fact that the experimenters mentioned had 
succeeded in keeping boiled organic liquids sterile in flasks to which 
the oxygen of the air had free access, the question of the possibility 
of spontaneous generation—heterogenests—still remained unsettled, 
inasmuch as occasionally a development of bacterial organisms did 
occur in such boiled liquids. 
This fact was explained by Pasteur (1860), who showed that the 
generally received idea that the temperature of boiling water must. 
destroy all living organisms was a mistaken one, and that, especially 
in alkaline liquids, a higher temperature was required to insure ster- 
ilization. His experiments showed that a temperature of 110° to 
112° C. (230° to 233.6° F.), which he obtained by boiling under a 
pressure of one and a half atmospheres, was sufficient in every case. 
These experiments, which have been repeated by numerous investi- 
gators since, settled the spontaneous-generation controversy ; and it 
is now generally admitted that no development of microdrganisms 
occurs in organic liquids, and no processes of putrefaction or fermen- 
tation occur in such liquids, when they are completely sterilized and 
guarded against the entrance of living germs from without. 
Pasteur at a later date (1865) showed that the atmospheric or- 
ganisms which resist the boiling temperature are in fact reproduc- 
tive bodies, or spores, which he described under the name of ‘‘ corpus- 
cles ovoides” or ‘‘ corpuscles brillants.” Spores had been previously 
seen by Perty (1852) and Robin (1853), but it was not until 1876 that 
the development of these reproductive bodies was studied with care 
by Cohn and by Koch. The last-named observer determined the 
conditions under which spores are formed by the anthrax bacillus. 
Five years later (1881) Koch published his valuable researches relat- 
ing to the resisting power of anthrax spores to heat and to chemical 
agents. 
