CULTURE MEDIA. 40 



The cylinder of potato rests upon the constricted portion of the tube, 

 as shown in Fig. 21. 



Sometimes a potato paste is employed. The potatoes are boiled 

 for an hour and the skins removed, after which they are mashed 

 with a little sterilized water, placed in suitable plates, and sterilized 

 by exposure for half an hour on three successive days in the steam 

 sterilizer. Bread paste may be made in the same way, and is a very 

 favorable medium for the growth of certain bacteria and also for the 

 common moulds. 

 4 



