BACTERIA CULTIVATION 



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Bacteria that grow best at a temperature of 37 C. (most of the 

 pathogenic ones do) develop more rapidly and luxuriantly in an 

 incubator, or thermostat. Indeed some organisms, like the tubercle 

 bacillus, cannot be cultivated without it. An incubator comprises, 

 an air chamber surrounded by a water chamber, and this, in turn, 

 is surrounded by another air chamber. It is essential that the 

 interior of the incubator be kept at an even, unvarying temperature. 



FIG. 25. Incubator. 



This is accomplished by using a small bunsen flame under the incu- 

 bator. The heat from the flame warms the outer air chamber or 

 jacket, and it in turn warms the water jacket, and the interior air 

 chamber, where the cultures are kept, is thus heated to the required 

 temperature. The amount of heat is automatically regulated by a 

 thermo-regulator, which diminishes the gas supply if the temper- 

 ature runs too high, or increases it if it runs too low. The Roux 

 regulator is the simplest and most efficient one. 



