VACCINE-THERAPY 



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6 inches from the bottom. Several varieties are in use. 

 The one we use is Koch's pattern, and answers all practical 

 purposes. A steam sterilizer is used for sterilizing culture 

 media. 



To sterilize media thoroughly, it must be exposed for half 

 an hour daily for three successive days. The first steaming 



Fig. 5. — Moist Heat Sterilizer (Koch). 



destroys all developed bacteria, the second destroys the 

 spore after it has developed into a germ, and the third kills 

 any bacteria which may not have developed from a spore 

 during the first interval. 



The Centrifuge. 



This is a most essential laboratory accessory, and there 

 are a variety on the market, but whether they are driven 

 by hand, water, or electricity, the principle is the same — 



