
88 THE EVOLUTION OF LIFE 
was extremely simple and yet perfectly suitable. 
The infusions with which trial was to be made were 
introduced into flasks with narrow necks; the necks 
of the flasks were drawn out and then hermetically 
sealed in the blow-pipe flame, while the flasks with 
their contents were subsequently heated in boiling 
water for different periods—with the view of killing 
any pre-existing living things, either in the fluids, in 
the air contained within the flasks, or on the walls 
of the vessels themselves. 
In 1837 another mode of experimentation was 
introduced by Schwann,! and has been much used 
since his time (either exactly or with slight modi- 
. fications), and prin- 
cipally by Pasteur 
and Jeffries Wyman. 
The organic matter in solution with 
which trial is to be made is boiled 
in a flask, the neck of which is 
securely connected with a_ tube 
closely packed with portions of red- 
hot pumice stone—or else closely- 
packed, fine, iron wires as employed 
by Wyman. And after the solution 
has been boiled for some time, so 
that all the air of the flask has been 
Wyman’s Modifica. expelled, the vessel itself is allowed 
tele ta aaa to cool slowly, while the tube con- 
taining the closely-packed red-hot 
materials is still maintained at the same tempera- 
ture, in order that the air entering slowly into 
1 Pogendorff’s Anunalen, 1837, vol. xli. p. 184. 


