THE METHODS OF STERILIZATION. 



79 



culture purposes, except after they have been submitted for 

 several days to the temperature of the human body in the 

 thermostat and remained sterile during this control-test. 



6. For generating dry heat for the sterilization of glass- 

 ware, implements, and instruments used in making cultures, 

 the hot-air oven and rose-burner are most usually employed, 

 and a temperature usually of 180 C, maintained in the oven 

 for one and one-half hours (Figs. 38 and 39). 



FIG. 41. 



Arnold steam sterilizer. (Abbott.) 



The oven consists of a double-walled metallic box, with a 

 double-walled front door, with a copper bottom, the sides and 

 door encased in asbestos boards. The heat is applied by 

 means of a rose gas-burner (Fig. 39) to the bottom of the box. 

 The objects to be sterilized are put upon perforated metallic 

 shelves in the box. In the top of the apparatus are two per- 

 forated openings for the insertion of the thermometers. In 

 this portion the oven is also provided with a perforated slid- 

 ing window to allow escape of the overheated air. 



