PLAXTS wniCB CAl'SE DEVAV ?, ,7) 



which is filled witli bacteria, place it in a wide -mouthed 

 bottle, and place in it a vial containing clear water, 

 and stopper the larger bottle as shown in Fig. 30. As 

 a control, use a similar arrangement with pure water 

 in place of the infusion. A still better arrangement is 





r j — ^- 



a 



212. Stab cultures iu gelatin: (a) air-loving bacteria, {&) bacteria not able to 

 grow in the presence of ail", (cj b.icteria which grow equally well with 

 or without air. 



to repeat the experiment described on page 34, Fig. 

 31, using the infusion in place of the seeds. 



We may now place some milk in vials or bottles, 

 close the mouths with cotton, and sterilize for ten 

 minutes on three successive days. Open one bottle 

 three days after the last sterilization, another a week 

 later, and another two weeks later. Do yon detect any 



