122 



BACTERIOLOGY 



perature sufficiently cool. In summer doubtless more ice will be 

 required. 



For heating, an ordinary i6-candle-power electric bulb is 

 used, and the electricity is obtained from the public supply. 

 The wire is run through one of the walls, and a part of the current 

 is made to operate a horse-shoe magnet, and another part is 

 conducted through the lamp used for heating. 



The accompanying diagram (Fig. 51), will serve to- show 

 the arrangement. 



A telegraph key is used to supply the horse-shoe magnet 



Ther.morea/ulator 

 FIG. 51. Diagram of electric regulator for low- temperature incubator. 



which is inserted in the heating circuit in such a way that when 

 the armature is attracted toward the magnet the circuit is com- 

 pleted and the lamp is consequently lighted. The part of the 

 current, a, supplying the magnet first passes through a small 

 lamp and through two resistance coils so as to red ace the current. 

 It then passes through the magnet, and is continued on to the 

 set-screw, b, which is so placed that when the thermoregulator 

 comes in contact with it the circuit is complete. The, regu- 

 lator consists of a strip of hard rubber and a strip of brass riveted 





