30 BACTERIOLOGY. 



bator reaches the required temperature, the mercury is 

 pushed up by means of the screw in the lateral arm, 

 until it closes the orifice, at the extremity of the vertical 

 portion of the T. The gas which passes through the 

 lateral orifice is sufficient to maintain the apparatus at 



FIG. 23. MEYER'S THERMO-REGULATOR. 



the temperature required. If the temperature of the 

 incubator falls the mercury contracts, and gas passing 

 through the terminal orifice of the T, the flame of the 

 burner increases and the temperature is restored. 



Meyer's thermo-regulator is represented in . Fig. 23. 

 I. shows the construction of the regulator ; its inner tube 



