30 



THE BACTERIOPHAGE AND ITS BEHAVIOR 



Plug the opening of the small tube with cotton, as one would a culture 

 tube (fig. 3). 



If it is not essential to make the filtration aseptically, the ultrafilter 

 is then ready for use. If sterihty is requisite, the filter must be steriKzed, 

 either as it is or after denitrification. 



<» 





Fig. 3. The Ultrafilter Ready for Sterilization 



Denitrification 



This detailed description of the preparation of ultrafilters is here 

 inserted because ultrafiltration must shortly become a common pro- 

 cedure in all experiments deaUng with ultraviruses, the group of beings 

 to which the bacteriophage belongs. That the description of the 



