S6 



MANUAL OF BACTERIOLOGY. 



about 112° to 120° C. Under these conditions culture-media 

 may be suflEiciently sterilized in the autoclave in fifteen minutes, 

 and at a single sterilization. The autoclave consists of a metal 

 cylinder with a movable top, which is fastened down tightly 

 during sterilization. It is furnished with a thermometer, a 

 pressure gauge, and a safety-valve which allows the steam to 

 escape if too high a pressure is attained. Heat is furnished by 



fmp%> 



Fig. 15. — Autoclave. 



a gas-burner underneath. The lower part of the cylinder 

 contains water. The objects to be sterilized are supported 

 above this water on a perforated bottom or shelf. 



It is necessary to follow certain precautions in the use of 

 the autoclave, especially during cooling. The apparatus 

 must not be opened while the steam contained within it is 

 still under pressure, as there may be a sudden evolution of 



