STERILIZATION 8 1 



of sterilization, as the discontinuous method, and sometimes 

 as Tyndallization. 



In this method culture media are subjected to a steriliza- 

 tion of from ten to twenty minutes on one day, allowed 

 to stand twenty-four hours and heated again, then allowed 

 to stand another twenty-four hours, and heated a third time. 

 This method almost invariably produces complete steriliza- 

 tion, providing, of course, the material has reached the proper 

 temperature throughout. Its efficiency depends upon two 

 things: first, the fact that streaming steam applied for ten to 

 twenty minutes kills all germ life not in the spore stage ; and, 

 second, standing twenty-four hours allows the spores, which 

 were not killed on the first application of steam, opportunity 

 for germination, so that on a second exposure the young 

 bacteria are killed. The third exposure for ten to twenty 

 minutes makes it almost certain that all spores have germi- 

 nated and have been killed. Evidently this method is not 

 applicable to all materials, since an essential feature is the 

 opportunity for the germination of the spores. It would be 

 impossible to sterilize empty glassware, instruments, ban- 

 dages, etc., by this method, since there is no opportunity on 

 these materials for the growth of the bacteria in the intervals 

 between heatings. 



This method of sterilization is carried out in a steamer, of 

 which there are a number of different types. All that is 

 necessary is a vessel which will hold water, which has a shelf 

 above the water, and a fairly tight cover. An excellent form, 



