42 



BACTERIA 



One or two thousand cubic centimetres of the water under 

 examination are passed through a sterilised Berkefeld filter 

 by means of siphon action or an air-pump. The candle of 

 the filter retains on its outer surface all, or nearly all, the 



Hot Air Steriliser 



For the Sterilization of Glass Apparatus, etc. 



particulate matter contained in the water. The matter thus 

 retained on this outer surface is brushed by means of a 

 sterile brush into lo or 20 cc. of sterilised water. Thus we 

 have all the organisms contained in two litres of the water 

 reduced into 10 cc. of water. From this, so to speak, con- 



