ASSIMILATION OF CARBON 63 



autoclave. The heat must be applied for an adequate period, and the temperature 

 must be sufficiently high. Liquids are frequently sterilized by passing them through 

 a suitable filter (such as the Chamberland), which retains the bacteria, etc. Steril- 

 ization may also be accomplished by the use of antiseptics or disinfectants, such as 

 mercuric bichloride, phenol, etc. These simply poison the microorganisms. 



6. Pure Cultures. — Pure cultures of any given kind of microorganism may be 

 obtained by inoculating a suitable sterile medium with a single cell of the form desired, 

 and allowing this to develop without the entrance of any other cells. Unless obtained 

 in this way, a culture cannot be surely considered as pure. Single-spore inoculation is 

 generally accomplished by repeated dilution of a liquid medium that contains the 

 particular form desired. For this sort of work special technique has been devised. 



