THE CULTIVATION OF MICRO-ORGANISMS 



IIQ 



heat and replaced with mercury so that the capillary EF, the bulb 

 at its lower end, and a small part of the large bulb J, are occupied, 

 by the mercury. Ether may be used when the regulator is not 

 to be heated above 35 C., alcohol when it is not to be heated 

 above 75 C., and toluol for temperatures between 75 and ico C. 

 A more satisfactory regulator is that of Roux. It is con- 

 structed entirely of metal, and its 

 operation is due to the unequal 

 expansion and contraction of two 

 metals which are riveted together. 

 Fig. 49 shows this regulator. The 

 gas passes in at e and passes out 

 at d. The amount of gas passing 

 through is regulated by a piston 

 on the end of the set screw inside 



FIG. 49. Roux bime- 

 tallic gas-regulator, a, Set 

 screw; b, Screw collar; c, 

 Clamp; d, Outlet for gas; 

 e, Inlet for gas. 



FIG. 50. Koch auto- 

 matic gas-burner. 



the tube from which the outlet tube branches off. This piston 

 moves in or out according to the changes of temperature of the 

 water jacket of the incubator into which the stem (/") of the regu- 

 lator is inserted. This stem is fenestrated and has the riveted 

 metallic strips running down in it. These strips are pivoted at 

 the collar, g. 



