ATMOSPHERE IN .RELATION TO PUTREFACTION AND INFECTION. 
51 
for Jive months they have remained without speck or turbidity. Other tubes similarly 
boiled, and placed underneath shades containing the floating matter of the air, have long 
since fallen into mould and rottenness. 
Turnip- and hay-infusions rendered slightly alkaline have been mentioned as parti- 
cularly prone to spontaneous generation. I wished to test this. On the 26 th of 
November, therefore, four shades were prepared, two containing strong turnip-infusion 
and hay-infusion unneutralized, two containing infusions which had been rendered 
slightly superneutralized by caustic potash. The alleged spontaneous development of 
life was not observed. The tubes exhibit to this hour the clearness and colour which 
they showed on the day they were boiled. Hermetically sealed tubes, containing the 
same infusions, prepared on the same day, remain equally clear ; while the specimens 
exposed to the laboratory air have fallen into rottenness. 
The experiments with calcined air were also executed in another form and on a larger 
scale. A “ propagating-glass,” similar to that already described, was cemented in the 
same way to a slab of wood through which passed twelve large test-tubes. The infu- 
sions, as before, were hay, turnip, beef, and mutton. The air being removed from the 
propagating-glass by a good air-pump, its place was supplied by other air which had 
passed slowly through a red-hot platinum tube containing a roll of platinum gauze, also 
heated to redness. Tested by a searching beam, this calcined air was found quite free 
from floating matter. For two months no speck invaded the limpidity of the infusions 
exposed to it, while a week’s exposure to the ordinary air sufficed to reduce twelve 
similar infusions, hung on to the slab of wood outside the glass, to rottenness. 
§ 20. Infusions withdrawn from Air. 
The arrangement was the same as that in the first experiment with filtered air, the 
only difference being that the bell-jar, with a view to its more perfect exhaustion, was 
smaller. It was cemented air-tight to a slab of wood through which passed three large test- 
tubes, filled to about two thirds of their capacity with infusions of beef, mutton, and turnip 
respectively. The air was pumped out six times in succession, and filled after each exhaus- 
tion with air carefully filtered through cotton-wool. While this air was in contact with 
the infusions they were boiled in a brine-bath. The receiver was afterwards exhausted 
as perfectly as a good air-pump could exhaust it ; while outside the receiver were hung 
three tubes to compare with those within. 
Here the protected infusions remained as clear as they were on the day of their in- 
troduction, not only after the exposed infusions had charged themselves with life, but 
for many weeks after they had evaporated away. 
Such, then, are the tests to which I have subjected the statement that “ boiled 
turnip- and hay-infusions exposed to filtered air, to calcined air, or shut off altogether 
from contact with air, are more or less prone to swarm with Bacteria and Vibriones in 
mdccclxxvi. i 
