58 



BACTERIOLOGY. 



the apparatus is closed, and it also requires time for 

 cooling after the desired exposure to such pressure be- 

 fore the apparatus can be opened. 



It is manifest that during these three periods, viz., 

 (a) reaching the pressure desired, (b) time during which 

 the pressure is maintained, and (c) time for fall of pres- 

 sure before the chamber can be opened, it is difficult to 

 say certainly to what temperature and pressure the arti- 

 cles in the apparatus have, on the whole, been subjected. 



FIG. 8. 



Steam sterilizer, pattern of Koch. 



Clearly, if the desired pressure and temperature have 

 been maintained for ten minutes, one cannot say that 

 this is all the heat to which the articles have been sub- 

 jected during their stay in the chamber. In this light, 



