122 BACTERIOLOGICAL LABORATORY TECHNIC 



may be fished out and transplanted to fresh culture tubes, and 

 after a few hours' growth they become pure cultures. An old 

 method employed in many laboratories, in breweries and orig- 

 inated by Pasteur was what is known as the dilution method. 



FIG. 29. Series of stab cultures in gelatine, showing modes of growth of 

 different species of bacteria. (Abbott.) 



Numerous flasks are inoculated by matter containing bacteria 

 very highly diluted in bouillon and by means of a sterile pipette 

 drops of this highly attenuated mixture are dropped into flasks 

 of sterilized bouillon or wort. Most of the flasks will show a 

 mixed growth but a few will show only one kind of organism. 



