ave had several
cases of survival after four and five hours' boiling, some survivals
after six, and one after eight hours' boiling. Thus far has
experiment actually reached; but there is no valid warrant for fixing
upon even eight hours as the extreme limit of vital resistance.
Probably more extended researches (though mine have been very
extensive) would reveal germs more obstinate still. It is also
certain that we might begin earlier, and find germs which are
destroyed by a temperature far below that of boiling water. In the
presence of such facts, to speak of a death-point of bacteria and
their germs would be unmeaning--but of this more anon.

'What present warrant,' it has been asked, 'is there for supposing
that a naked, or almost naked, speck of protoplasm can withstand four,
six, or eight hours' boiling?' Regarding naked specks of protoplasm I
make no assertion. I know nothing about them, save as the creatures
of fancy. But I do affirm, not as a 'supposition,' nor an
'assumption,' nor a 'probable guess,' nor as 'a wild hypothesis,' but
as a matter of the most undoubted fact, that the spores of the hay
bacillus, when thoroughly desiccated by age, have withstood the ordeal
mentioned. And I further affirm that these obdurate germs, under the
guidance of the knowledge that they are germs, can be destroyed by
five minutes' boiling, or even less. This needs explanation. The
finished bacterium perishes at a temperature far below that of boiling
water, and it is fair to assume that the nearer the germ is to its
final sensitive condition the more readily will it succumb to heat.
Seeds soften before and during germination. This premised, the simple
description of the following process will suffice to make its meaning
understood.

An infusion infected with the most powerfully resistent germs, but
otherwise protected against the floating matters of the air, is
gradually raised to its boiling-point. Such germs as have reached the
soft and plastic state immediately preceding their development into
bacteria are thus destroyed. The infusion is then put aside in a warm
room for ten or twelve hours. If for twenty-four, we might have the
liquid charged with well-developed bacteria. To anticipate this, at
the end of ten or twelve hours we raise the infusion a second time to
the boiling temperature, which, as before, destroys all germs then
approaching their point of final development. The infusion is again
put asid