1 8 CULTURE METHODS AND TECHNIQUE 



quantities of media should be sterilized three times. Between the 

 periods of sterilization media should be placed at a temperature 

 favorable for most bacterial development, and not in a cold place, 

 this being in order that any spores might pass into the vegetative 



Fig. 50. Autoclave, Erect Type, Clamped Top, heated by Gas 

 (Photograph by Geo. M. Reed) 



state within twenty-four hours, and thus be killed at the next 

 sterilization. 



A suggestion which has been made by Theobald Smith is of 

 interest in connection with the sterilization of media which may con- 

 tain anaerobic bacteria. If such media are sterilized in thin layers, 

 oxygen may have comparatively free access to any submerged 



