VITALITY OF PUTEEFACTIVE ORGANISMS. 193 



would seem complete, but a repetition of the experi- 

 ments — and I never felt safe without frequent and varied 

 repetition — would, as before, present the success in the 

 light of an accident. I am, however, secure in stating 

 that while pursuing this plan I have in some cases 

 effected complete sterilization by an amount of boiling 

 which, in other cases, though twenty times multiplied, 

 has failed to produce this effect. I have, for example, 

 placed side by side in my collection two series of organic 

 infusions, one as pellucid as distilled water, having 

 been rendered permanently sterile by an exposure to 

 the boiling temperature for five and ten minutes, and 

 a second series containing the same infusions boiled for 

 30, 120, and 330 minutes respectively, and which never- 

 theless are muddy throughout and covered with scum. 

 Even here, however, causes, other than differences of 

 manipulation, may have contributed to the result. 



Weeks of labour have been devoted to these experi- 

 ments, nor did they exhaust the trials actually made. 

 Another mode of proceeding was this. Pipette-bulbs 

 were prepared 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 after- 

 wards heated almost to redness in the flame of a Bunsen 

 lainp. 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. A great number of experiments were 



