BACTERIA. 47 



sterilized glass plate and expose the cut sur- 

 face to the air for an hour. A.t the end of 

 this time cover with a hell-jar that has been 

 sterilized, and put under this some (steril- 

 ized) liquid to make a moist atmosphere. 



Examine from day to day for ten days or 



two weeks. Record results and explanation. 



Put some freshly-made hay infusion into 



e/ / *7 t/ 



three (previously labelled) test-tubes (a), (b), 

 (c). Stop them securely with cotton. 



(a) To be set aside. 



(b) To be boiled once for 3-5 minutes. 



(c) To be boiled for 35 minutes three or 



four times at intervals of nine or 

 ten hours. 



Keep all three side by side. Watch carefully 

 for any changes that may appear. Describe 

 briefly, with explanation. 



