46 



APPLIED BACTERIOLOGY 



In this case the water is collected in the open vessel in 

 which the tubes D and E stand, and is conducted by the 

 pipe H H' to the waste-pipe N without producing any 

 effect whatever on the incubating chamber. 



If the temperature of the room in which the incubator is 

 placed is above the boiling-point of the capsule, the 

 horizontal tube will continue to travel towards the left, so 

 that presently the water will run down the tube E, along the 

 tube E', and, passing through the ice-box, will so lower the 



Fig. 9. — ^Plan op Cool Incubator. 



inside temperature that the capsule will collapse a little and 

 cause the flowing water to again take up a position midway 

 between the two tubes. 



A fraction of a degree is quite sufficient to determine 

 which tube the water will fall into, so that the interior of 

 the apparatus remains at a practically uniform tempera- 

 ture. 



We have thus, so to speak, a reservoir of heat in the 

 boiler and a reservoir of cold in the ice-box, which the 



