PERSISTENCE OF PUTREFACTIVE AND INFECTIVE ORGANISMS. 
169 
I fully expected that the majority of these chambers would prove sterile. I did not 
expect to find them all in this condition, because the chambers had been put together in 
the laboratory, the air of which must have deposited its germs not only on the glycerine- 
coated interior of the chambers, but also on the inner surfaces of the test-tubes. My 
expectation, moderate as it was, was not realized. The only noticeable peculiarity in 
the deportment of the infusions was that they yielded tardily, hut in the end every one 
of them, without exception, broke down. 
Was the infection in this case derived from the air of the store-room % I think not ; 
and for this reason : — On the 27th of December four hermetically sealed flasks, charged 
with a cucumber-infusion which had remained perfectly pellucid for some weeks, were 
opened in the store-room ; four similar flasks, charged with the same infusion, were 
opened at the same time in the laboratory. On the 31st of December the whole 
group of the latter four was found invaded by organisms, while those opened in the 
store-room contracted no infection and developed no life. I do not think, therefore, 
that the air of the store-room had any thing to do with the contamination of the 
infusions contained in the closed chambers, but that the contagium already existed in 
the chambers when they were taken down stairs. They acted as infected houses placed 
in a salubrious air. 
§ 12. Infusions protected by Glass Shades containing calcined Air. 
I have already described this mode of experiment *. The shades stood upon circular 
plates of wood, each supported on a tripod (see fig. 6). 
Under each shade were two upright rods of stout copper 
wire, and stretching from rod to rod was a spiral (p) of 
platinum wire. The copper wires passed through the slab 
of wood, their free ends being in the air. The rim of each 
shade was surrounded by a collar of tin attached by wax 
to the slab, with a space of about half an inch between the 
collar and the glass. After the introduction of the infusions 
and the mounting of the shades, this annular space was 
packed with cotton-wool. The aim here was to destroy 
the floating matter of the air by the incandescent platinum 
spiral. The air heated by the spiral would of course expand, 
passing outwards through the cotton-wool, while the air 
reentering, on the cooling of the shade, would be duly sifted 
by the wool. In my former experiments five minutes’ incan 
descence sufficed to render the air absolutely inoperative on 
infusions exposed to its action. 
In the present experiments the period of incandescence 
was doubled, ten minutes being allowed instead of five, 
* Phil. Trans, vol. clxvi. p. 50. 
