414 ELEMENTARY BIOLOGY. [ CHAP - XH. 



8. Place some fresh-made hay infusion in three flasks; 

 boil two of them for three or four minutes, and while 

 one is boiling briskly stop its neck with a plug of 

 cotton-wool and continue to boil for a minute or 

 two: leave the necks of the other two flasks un- 

 closed, and put all three away in a warm place. 



a. In a day or two abundant Bacteria will be found 

 in the unboiled flask. 



b. In the boiled but unclosed flask Bacteria will 

 also appear, but perhaps not quite so soon as 

 in a. 



c. In the flask which has been boiled and kept 

 closed Bacteria will not appear, if the experi- 

 ment has been properly performed, even if it be 

 kept for many months. 



