FILLING THE TUBES. 129 



As soon as the tubes have been filled they are to be 

 sterilized in the steam sterilizer for fifteen minutes on 

 each of three successive days. During the intervening 

 days they may be kept at the ordinary room-tempera- 

 ture. 



When sterilization is complete and the medium in 

 the tubes is still liquid, some of them may be placed in 

 a slanting position, at an angle of about ten degrees 

 with the surface 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. 



For Esmarch tubes not more than 5 c.c. of material 

 should be placed in each tube, as more than this renders 

 it difficult to distribute the gelatin evenly over the inner 

 surface of the tubes when they are rolled. 



9 



