xtracts purer than
ever cook manufactured. Three days' exposure to the dusty air
suffices to render them muddy, fetid, and swarming with infusorial
life. The liquids are thus proved, one and all, ready for
putrefaction when the contaminating agent is applied. I invite my
colleague to reflect on these facts. How will he account for the
absolute immunity of a liquid exposed for months in a warm room to
optically pure air, and its infallible putrefaction in a few days when
exposed to dust-laden air? He must, I submit, bow to the conclusion
that the dust-particles are the cause of putrefactive life. And
unless he accepts the hypothesis that these particles, being dead in
the air, are in the liquid miraculously kindled into living things, he
must conclude that the life we have observed springs from germs or
organisms diffused through the atmosphere.

The experiments with hermetically sealed flasks have reached the
number of 940. A sample group of 130 of them were laid before the
Royal Society on January 13, 1876. They were utterly free from life,
having been completely sterilised by three minutes' boiling. Special
care had been taken that the temperatures to which the flasks were
exposed should include those previously alleged to be efficient. The
conditions laid down by the heterogenist were accurately copied, but
there was no corroboration of his results. Stress was then laid on
the question of warmth, thirty degrees being suddenly added to the
temperatures with which both of us had previously worked. Waiving all
protest against the caprice thus manifested, I met this new
requirement also. The sealed tubes, which had proved barren in the
Royal Institution, were suspended in perforated boxes, and placed
under the supervision of an intelligent assistant in the Turkish Bath
in Jermyn Street. From two to six days had been allowed for the
generation of organisms in hermetically sealed tubes. Mine remained
in the washing-room of the bath for nine days. Thermometers placed in
the boxes, and read off twice or three times a day, showed the
temperature to vary from a minimum of 101 deg. to a maximum of 112 deg. Fahr.
At the end of nine days the infusions were as clear as at the
beginning. They were then removed to a warmer position. A
temperature of 115 deg. had been mentioned as particularly favourable to
spontaneous generation. For fourteen days the temperature of the
Turkish Bath hovered about this point, fall