PERSISTENCE OF PUTREFACTIVE AND INFECTIVE ORGANISMS. 
183 
§ 19. Final proof that the Resistant Germs are embraced by the Infusion. Examples of 
Resistance both in Acid and Neutral Liquids. 
I have here touched upon the question which chiefly harassed me at the time to which 
1 now refer. It was this: — Have the germs, which under the circumstances here 
described produced life, been really embraced by the infusion itself during the time of 
heating 1 The liquid, it will be remembered, had to pass through the neck of the bulb, 
and it could not descend from the neck into the bulb without leaving a film adherent to 
the internal surface of the neck. This film, I reflected, might dry in part by evaporation ; 
it might, in doing so, leave germs behind which would be very differently circumstanced 
from those in the liquid. To germs thus exposed, not to the heat of water, but to the 
possibly less effective heat of vapour and air, the observed life might I thought be due. 
Before closing definitely with the proposition that the surviving germs had actually been 
in the liquid, the possibility to which I have just referred had to be shut out. 
The evil was to some extent mitigated by a suggestion of my assistant to charge the 
bulb, not through its own neck, but through a narrow tube issuing at right angles to 
the neck. But even here a portion of the neck and of the higher interior surface of 
the bulb was trickled over by the infusion. The difficulty was finally met by causing 
the lateral tube to issue from the centre of the bulb itself, and forcing the infusion into 
the bulb by atmospheric pressure, until the surface of the liquid stood clearly above 
the lateral orifice. To this level the liquid rose without wetting any portion of the 
surface against which it did not permanently rest. 
The precise method pursued in preparing and charging the bulbs was this : — First, 
the bulb as sent to us by the glass-blower is represented at A, fig. 10. Its neck is first 
plugged with cotton-wool ( c ) and hermetically sealed as at B, fig. 10. The lateral 
tube is then drawn out to almost capillary narrowness at o and p. The end n is con- 
nected with an air-pump, by which the bulb is exhausted, and after two or three 
emptyings and fillings, it is finally charged with one third of an atmosphere of thoroughly 
filtered air. While the pump attached to n maintains this pressure within the bulb, 
the capillary tube p is sealed with a lamp. The bulb and its appendages are then 
heated nearly to redness in a Bunsen flame, all life adherent to the interior surface 
being thus destroyed. 
The end p is then introduced into the infusion, pressed against the bottom of the 
vessel that contains it, and thus broken. The external pressure of a whole atmosphere, 
having but one third of an atmosphere within the bulb to oppose it, forces the liquid 
through the lateral tube. It enters the bulb, gradually rising until it reaches the 
orifice, and rises above it. When the pressure within is exactly equal to the pressure 
without, two thirds of the bulb are occupied by the liquid. 
The infusion then extends without breach of continuity from the bulb B to the vessel 
in which the end p is immersed, the uncleansed air being thus completely excluded. 
A small gas-flame is carefully applied at o. The liquid within the narrow tube vaporizes, 
and the vapour drives the liquid to some distance right and left from the place of 
2 d 2 
