88 VETERINARY BACTERIOLOGY 



This method of sterilization is commonly used for the removal of 

 bacteria from culture-media when it is desired to study their 

 soluble metabolic products, and in the removal of bacteria from 

 sera which contain antitoxins and other antibodies. It is not 

 commonly used in the sterilization of media intended for the 

 cultivation of bacteria. Filters of this character have been used 

 extensively in the filtration of water for drinking purposes. When 

 first installed, they are quite efficient, but it is found that the organ- 

 isms rapidly penetrate, and in the course of time are found in the 

 filtrate. Such filters must, therefore, be sterilized at intervals if 

 they are to remain efficient. 



