VITALITY OF PUTREFACTIVE ORGANISMS. 213 



final development. At each subsequent period of heat- 

 ing the number of living germs is diminished, until 

 finally they are completely destroyed; The infusion, if 

 protected from external contamination, remains for ever 

 afterwards unchanged, although, when living Bacteria, 

 a sprig of hay, or even the dry dust particles of the 

 laboratory are sown in it, the sterilized liquid shows its 

 power both of enabling the fully developed organism to 

 increase and multiply, and of developing the desiccated 

 Bacterial germ into multitudinous Bacterial life. 



On the same date an experiment was made with a 

 series of pipette-bulbs, whose necks were so bent and 

 plugged with cotton-wool that no impftrity from the 

 wool could fall into the infusion. Four bulbs were 

 charged with an infusion of Heathfield and four with an 

 infusion of London hay, samples of the same infusions 

 being introduced at the same time into another series 

 of bulbs which were plugged like their neighbours and 

 subjected continuously to the boiling temperature for 

 ten minutes. The eight bulbs first referred to were, on 

 the contrary, discontinuously boiled, the sum of their 

 periods of boiling being four minutes. The result is 

 that while the entire series of bulbs boiled for ten 

 minutes gave way within forty-eight hours after their 

 preparation, seven out of the eight bulbs which had been 

 subjected to discontinuous boiling remained permanently 

 brilliant. 



On the 3rd of February, with the view of testing the 

 new method still further, infusions of our most refrac- 

 tory kinds of hay were prepared. There were five bulbs 

 of neutralized Guildford infusion, and five of a neutral- 

 ized infusion formed from a mixture of old Colchester 

 and old Heathfield hay. Two bulbs of each infusion 

 were at the same time charged and subjected to the 

 boiling temperature for ten minutes. The ten bulbs 



