136 BACTERIOLOGY 



minutes on each of three successive days, being kept during 

 the intervals at room temperature, or they may be sterilized 

 by a single exposure of 15 minutes in the autoclave to a 

 temperature equivalent to steam under about one atmosphere 

 of pressure. 



When sterilization is complete and the medium in the 

 tubes is still liquid, some of them may be placed in a slant- 

 ing position, at an angle of about ten degrees with the sur- 

 face on which they rest, and the medium allowed to solidify 

 in this position. These are for the so-called slant-cultures. 

 The remainder may solidify in the erect position; these 

 serve for making plates. 



