44 



ESSENTIALS OF BACTERIOLOGY. 



denotes sufficient sterilization. All instruments, where practi- 

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

 Bunsen burner. One hour in the oven at 170 C. usually steri- 

 lizes glass-ware, while the ordinary germs in liquids may be 



FIG. 15. 



Koch's Steam-chest. 



killed by boiling for five minutes if no spores are present. The 

 boiling of any fluid at 100 C. for one and one-half hours nearly 

 always ensures sterilization. 



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

 to be a very effective application of heat. 



