182 
PROFESSOR TYNDALL ON THE DEPORTMENT AND VITAL 
outrush of air from a which bubbled through the liquid. As soon as the bubbling had 
relaxed a little, a being still submerged, the bulb was transferred to iced water. A 
shrinking of the warm air was the consequence, and through a the infusion was forced 
by atmospheric pressure. It descended the middle branch of the T-tube, and was dis- 
charged from its end e into the bulb. The quantity of liquid obtained by a first immer- 
sion in the iced water was not sufficient to charge the bulb ; but by repeating the process 
of heating and chilling two or three times, the point a never being permitted to quit the 
infusion, any required quantity was with ease and accuracy introduced. The neck of the 
bulb was finally detached from the T-piece by loosening the india-rubber tube t. The 
bulb was then slightly warmed so as to cause an outflow from within, and while this 
outflow continued the neck was plugged with cotton-wool. It was sealed above the 
plug, and after the cooling of the infusion the sealed end was broken off with a file. 
It is not my intention to take up the Society’s time in describing in detail the 
numerous experiments made in accordance with this method, or the variety of infusions 
employed in testing its efficacy. Suffice it to say that, notwithstanding all my care, 
the results were chequered throughout. Sometimes success would seem complete, but 
a repetition of the experiments — and I never felt safe without frequent and varied 
repetition — would, as before, present the success in the light of an accident. I am, how- 
ever, secure in stating that by pursuing this plan I have in some cases effected complete 
sterilization by an amount of boiling which, twenty times multiplied, has failed to 
produce this effect when less accurate methods were resorted to. I have for example 
placed side by side in my collection a series of organic infusions as pellucid as distilled 
water which have been rendered permanently sterile by an exposure to the boiling 
temperature for five and ten minutes respectively, and a second series containing the 
same infusions boiled for 30, 120, and 330 minutes respectively, and which nevertheless 
are muddy throughout and covered with scum. 
Weeks of labour have been devoted to these experiments, nor did they exhaust the 
trials actually made. Another mode of proceeding was this. Pipette-bulbs were pre- 
pared by having a portion of their necks drawn out to a tube of very fine bore. The 
open end being connected with an air-pump, the bulb was exhausted and filled with 
filtered air several times in succession. In the final experiment the bulb was charged 
with one third of an atmosphere of cleansed air ; and while this pressure was maintained 
by the air-pump the narrow tube was hermetically sealed. Each bulb was afterwards 
heated almost to redness in the flame of a Bunsen lamp. It was charged by inverting 
the bulb, dipping the sealed end into the infusion, and breaking it off underneath the 
surface. The liquid entered until the bulb was two thirds filled, when the narrow tube 
was again sealed without permitting its open end to quit the infusion. A great number 
of experiments were thus executed, the results of which distinctly favoured the conclu- 
sion, though they did not to my satisfaction prove it, that the resistant germs were not 
to be wholly ascribed to the air, but that they had survived in the liquid. 
