

TYNDALL’S EXPERIMENTAL EVIDENCE 217 
Proceedings of the Royal Soczety, there is printed a 
note ‘‘On Heat as a Germicide when Discon- 
tinuously Applied,” in which Professor Tyndall said : 
‘Following up the plain suggestions of the germ- 
theory, I have been able, even in the midst of a 
virulently infective atmosphere, to sterilise all the 
infusions by a temperature lower than that of boiling 
water... . Before the latent period of any of the 
germs has been completed (say a few hours after the 
preparation of the infusion), I subject it for a brief 
interval to a temperature which may be under that 
of boiling water. Such softened and vivified germs 
as are on the point of passing into active life are 
thereby killed ; others not yet softened remain intact. 
I repeat this process well within the interval neces- 
sary for the most advanced of those others to finish 
their period of latency. The number of undestroyed 
germs is further diminished by this second heating. 
After a number of repetitions, which varies with the 
character of the germs, the infusion, however obstinate, 
2s completely sterrlised.” 
Noting by the way that the “character of the 
germs” has no other reality than Professor Tyndall 
chooses to infer from the obstinacy of the infusion 
in resisting sterilisation, it is only necessary further 
to point out that the above procedure and its results 
allow absolutely no conclusion to be drawn in favour 
of the survival of germs, except by ignoring the only 
other legitimate interpretation. The frequent repeti- 
tions of destructive heating, at or close to the boiling- 
point, might, after a time, repress all tendency to 
1 No, 178, vol. xxv. p. 569. 
