VITALITY OF PUTEEFACTIVE ORGANISMS. 195 



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 per- 

 manently rest. 



The precise method pursued in preparing and 

 charging the bulbs was this : — Fii'st, the bulb as sent to 

 us by the glass-blower is represented at a, fig. 20. Its 

 neck is first plugged with cotton-wool (c) and hermetic- 

 ally sealed as at b, fig. 20. The lateral tube is then 

 drawn out to almost capillary narrowness at o and jp. 

 The end n is connected 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 j) 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 jp 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 con- 

 tinuity from the bulb B to the vessel in which the end 

 p is immersed, the uncleansed air being thus completely 



