180 
PROFESSOR TYNDALL ON THE DEPORTMENT AND VITAL 
§ 18. Change of Apparatus. New Experiments with Filtered Air. 
The source of possible error referred to in the last section had been long present to my 
mind, and I had already taken measures to avoid it. On the 2nd of January, 1877, an 
infusion of turnip (sp. gr. 1006) and an infusion of melon (sp. gr. 1008) were prepared 
and introduced into a series of pipette-bulbs in the following manner: — One end 
#, fig. 8, of a glass T-tube was connected with an air-pump, the other end b was 
closely plugged with cotton-wool, while to the third branch of the T-tube the neck of 
the pipette-bulb A was attached by india-rubber tubing. A piece of the same tubing, 
furnished with a pinchcock y?, was also attached to the free end of the T-tube beyond 
the cotton-wool. 
The bulb A was exhausted three times in succession, the pinchcock p being closed, 
and was three times filled with filtered air, the pinchcock being opened. At the third 
exhaustion the bulb was raised to a very high temperature by a Bunsen flame, and 
finally filled with filtered air. It was then 
plunged for a minute into ice-cold water, 
from which it was afterwards removed, de- 
tached from the T-tube, and then charged 
with the infusion by means of a narrow 
pipette, fe, shown at the top of B, fig. 8. 
The rationale of the above proceeding 
is this :■ — On quitting the ice-cold water 
for the warmer air of the laboratory, ex- 
pansion of the air within the bulb would 
occur. This would cause a gentle motion 
from within outwards, opposing all in- 
draught of contaminated air. The entry 
of the infusion into the bulb would, I 
thought, also promote this outward 
motion. On the removal of the pipette, 
which occupied but a very small portion 
of the neck of the bulb, a little warmth 
was applied to the latter, and during its 
application the neck was plugged with 
cotton-wool. The air entering through 
this plug to supply the place of the small 
quantity displaced by the warmth would, 
I concluded, reach the interior of the bulb perfectly sifted of its floating matter. The 
necks of the bulbs were hermetically sealed, and the infusions maintained for ten minutes 
at the temperature of boiling water. After a lapse of twelve hours their sealed ends were 
broken off by means of a file. 
In our experiments on the 28th of December turnip and melon subjected to ten 
A B 
