266 



PRACTICAL DAIRY BACTERIOLOGY 



soda or powdered soap. After boiling, wash well in hot water 

 and then rinse thoroughly in clear cold water; drain and allow 

 to dry. 



The student may begin by thus washing 50 test tubes (Board 

 of Health pattern, Fig. 68), 2 liter flasks, i dozen Petri dishes 

 and several i c.c. pipettes. After drying, plug the test tubes and 



FIG. 69 PIP- 

 ETTE AND 

 GLASS TUBE 

 TO HOLD 

 SAME WHEN 

 STERILIZED. 



FIG. 70 HOT AIR STERILIZER 



flasks with cotton, place the pipettes in pieces of glass tubing 

 closed at one end and plugged with cotton at the other (Fig. 69). 

 Place all the articles in the sterilized oven (Fig. 70), and heat 

 to 155 C. (310 F.) for one hour. This sterilizes them and 



