12 LABORATORY GUIDE IN BACTERIOLOGY 



Steam is applied in two ways. The first method is 

 that of exposing media to steam of 100 C. for 20 min- 

 utes. This is done in an apparatus generally known as 

 the Arnold steam sterilizer. The usual form is illus- 

 trated in Figs. 6 and 7. Fig. 6 shows the appearance 



FIG. 5 

 Lautenschlager Hot-Air Sterilizer 



of the ordinary form with the hood off. Fig. 7 shows 

 the inside arrangement. The two compartments, a 

 and b, are connected by small holes, and a certain 

 amount of water has to be kept here. The water is 

 brought to a boil and the steam rises through a number 

 of holes in the bottom (c) into the chamber (d). The 

 steam condenses at the top and returns between two 



