186 THE FLOATING-MATTER OF TfflE AIR. 



The result here was that at the 6th bulb, which cor- 

 responded to three hours' boiling, the life-development 

 suddenly ceased. All the bulbs boiled from 15 minutes 

 to 180 minutes inclusive proved fruitful; while from 240 

 minutes to 360 inclusive all were completely sterilized. 

 As in the case of the turnip-infusion, the cucumber sub- 

 jected to long periods of boiling assumed an orange- 

 brown tinge. 



Comparing these results with those obtained with 

 the turnip-infusion, it will be observed that cucumber 

 and turnip exhibit about the same resistant power : 

 three hours' boiling, and less, failed to sterilize both of 

 them ; four hours' boiling, and more, rendered both of 

 them permanently barren. 



The cucumber-infusions prepared on the 22nd and 

 28th of February were connected with the atmosphere 

 through the cotton-wool plugs ; but no attempt had 

 been made to remove its floating matter from the air 

 above the infusions. On the 22nd, however, four bulbs 

 of the infusion were also prepared, charged with filtered 

 air, left unplugged, and hermetically sealed. The same 

 was done with four bulbs on the 28th of February. Each 

 group was subjected to periods of boiling of 15, 30, 

 45, and 60 minutes respectively. All of them became 

 turbid ; but it was interesting to notice the gradual and 

 obvious fall of life from the 15-minutetothe60-minute 

 period. Could the Bacteria have been counted, and 

 the result graphically represented, the ordinate corre- 

 sponding to the abscissa 15 would have been found very 

 considerably longer than that corresponding to the 

 abscissa 60. 



The method of experiment here for the most part pur- 

 sued was employed by Spallanzani and Needham. It 

 was afterwards extensively applied by the late excellent 



