78 



Mr. E, C. Grey. Decomposition of 



the emulsion. The flask was sterilised while^plngged with cotton wool, and 

 after the introduction of the bacteria the cotton wool plug was replaced by 

 the stopper seen in the figure. The practice has always been adopted of 

 either sterilising the stopper separately by steam or flaming the tubes and 

 rubber previous to its introduction into the flask, but it is almost certain that 

 this precaution is unnecessary, since the size of the population of bacteria 

 introduced at the beginning of the experiment precludes the possibility of 

 the results being appreciably influenced by subsequent contamination even 

 should such occur. This is one of the great advantages of the new technique. 



H 



At the beginning of the experiment the pinchcock of the tube A is closed 

 and the tube B connected to the water-pump. By this means the air in the 

 flask is exhausted, the solution being brought to the boil under the reduced 

 pressure. The tap B is then closed and, the tube A having been put into 

 communication with a reservoir of nitrogen, the pinchcock is opened and 

 nitrogen allowed to enter to replace the air which has been removed. The 

 operation is repeated a second and third time to ensure complete removal of 

 oxygen from the flask either in the gas space or dissolved in the solution. 



