28 



LABORATORY GUIDE IN BACTERIOLOGY 



autoclave for 5 minutes at 120 C. After sterilization 

 the blue is usually more or less lost, but returns upon 

 standing. 



EXERCISE 6. PREPARATION OF POTATO 



i. Select several large potatoes, and cleanse by 

 brushing the dirt off, cutting out the eyes and other 

 blemishes, and washing in water. 



FIG. 15 



Potato Cylinder 



(showing diagonal for 



cutting) 



FIG. 16 FIG. 17 



Ordinary Style of Potato Tube Potato Tube 

 a. Potato b. Cotton 



2. Punch out cylinders with a borer of suitable size, 

 trim them, and cut each cylinder into two equal parts 

 on a diagonal line (Fig. 15). 



