52 APPLIED BACTERIOLOGY 



thermostat draws upon according to the requirements 

 of the incubating chamber. When it is desired to work at 

 a temperature below the temperature of the external air, it 

 is essential that the ice-box B be kept supplied with ice. 

 When the temperature required is above that of the 

 external air, the lamp or gas must be lighted under the 

 boiler F. If the required temperature be at or near the 

 mean of the external air temperature, both ice and flame 

 will be necessary to correct the gain or loss of heat due to 

 external variations. 



In starting the apparatus, water must be poured into the 

 boiler F until it overflows at the waste-pipe. If it be 

 desired to cool the water, ice may be placed in the boiler, 

 or some of the water may be poured in through the ice- 

 box. 



If it be found that the water is not cool enough by the 

 time that the incubator is filled, run some water through 

 the ice-box. When the temperature inside the incubator 

 is 5° below the boiling-point of the capsule, the adjustments 

 can be made, but not before. The middle row of figures on 

 the ticket inside the door indicates the critical or boiling- 

 point of the capsule in degrees Fahrenheit. 



If the water be cooled too much, that is of no consequence, 

 as the object in first cooling the apparatus is to collapse the 

 capsule. 



Whilst the capsule is thus in a collapsed condition, the 

 milled head- screw P must be turned until the stream of 

 water runs down the centre of the tube D. In this position 

 the running water will be directed towards the boiler, and, 

 being heated, will in that condition pass into the water- 

 jacket of the apparatus. 



Having been thus adjusted, the milled head-screw P 

 must not be further interfered with during the whole time 

 that the apparatus is in use. After a lapse of two or three 



