VACCINE-THERAPY 



9 



cork at the top of the incubator, entering the air chamber. 

 The mercury rises and cuts off, or rather limits, the supply 

 of gas entering the burner, and so regulates the heat- 

 supply. The regulator in the writer's possession is in itself 

 regulated by a small screw, so that the temperature may 

 be set at any desired degree. The incubator should 

 be provided with double doors, the inner one of which 

 should be made of glass. The cultivation of bacteria 

 usually takes place in the laboratory at two temperatures — ■ 

 i.e., 20° C. (68° F.), suitable for those germs which grow out- 



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Fig. 3. — Thermo Regulator. 



side the animal body; and 37° C. (98-6° F.), or body tem- 

 perature. All media are suitable for the higher temperature 

 save gelatin, which melts at about 25° C. 



It must also be remembered that bacteria do not grow 

 well in sunlight ; they should therefore be incubated in the 

 dark. 



Sterilizers and Sterilization. 



There are two kinds of sterilizers in use — i.e., dry and 

 moist. 



