CHAPTER II 



BACTERIOLOGY 



The control of temperature within close limits is 

 very important in laboratories where bacteriological 

 investigations of the micro-organisms of dairy prod- 

 ucts are conducted. In many instances the success 

 in the maintenance of cultures depends upon the 

 ability continuously to maintain a constant tem- 

 perature. 



The micro-organisms of dairy products are grown 

 on various food materials known as media. To se- 

 cure the proper temperature for growth they are 

 usually placed in an insulated box known as an in- 

 cubator, and the temperature is regulated by an 

 electric thermostat, fan and ice. 



Each incubator is usually fitted with a seven-day 

 recording thermometer. The recording elements are 

 mounted on the wall outside of the incubator and 

 the capillary tube passes through the wall, the bulb 

 being located near the top and in the center of the 

 incubator. The charts taken from the recorder are 

 examined and any variations in temperature be- 

 yond the prescribed limits are noted, with the time 

 at which the variations occurred. 



The value of a continuous temperature record in 

 the process of incubating cultures lies in the fact 

 that such records not only show the temperature at 

 all times throughout the period of incubation, but 

 they are dated and can be filed for reference. It is 

 thus possible to determine with accuracy the tem- 

 perature maintained in the incubating process on 

 any previous date. 



