STERILIZA TION AND DISINFECTION. 



95 



a pressure of two or three atmospheres sufficient heat is 

 generated to destroy the spores. The objections to this 

 method are that it sometimes turns the agar-agar dark, 

 and that it is likely to destroy the gelatinizing power of 

 the gelatin, which after sterilization remains liquid. 



FIG. 12. Pasteur-Chamberland filter arranged to filter under pressure. 



lyiquids may also be sterilized by filtration i. e. by 

 passing them through unglazed porcelain or some other 

 material whose interstices are sufficiently fine to resist the 

 passage of the bacteria. This method is largely employed 



