42 



ESSENTIALS OF BACTERIOLOGY. 



and J foot deep. In them, glassware, cotton, and paper can be 

 sterilized. When the cotton is turned slightly brown, it usually 

 denotes sufficient sterilization. All instruments, where practi- 

 cable, should be drawn through the flame of an alcohol lamp or 

 Bunsen burner. 



Moist Heat. Steam at 100 C. in circulation has been shown 

 to be a very effective application of heat. 



Koch's Steam-chest. Circulating steam is obtained by aid of 

 Koch's apparatus. This consists of a cylindrical tin chest 



FIG. 15. 



Koch's Steam-chest. 



about 2 feet high and about foot in diameter ; divided in its 

 interior by a perforated diaphragm, a, an upper chamber for 



