UNITED STATES DEPARTMENT OF AGRICULTURE 



m BULLETIN No. 951 



^Ml^^jif^? Contribution from the Bureau of Animal Industry "^ 



Contribution from the Bureau of Animal Industry 

 JOHN R. MOHLER, Chief 





Washington, D. C. 



PROFESSIONAL PAPER 



June 4, 1921 



METHODS FOR CLOSE AUTOMATIC CONTROL OF 



INCUBATING TEMPERATURES IN 



LABORATORIES. 



By John T. Boavex, Technologist, Dairy Division. 



CONTENTS. 



Page. 



Constimction of temperature-control 



compartment 



Construction of room 



Heating equipment 



Page. 

 Description of temperature-control 



systems 7 



Temperature recorders 11 



Cost of operation iG 



The automatic control of temperature within close limits is A'ery 

 important in many lines of commercial work. It is of special im- 

 portance, in fact, is a necessity, in laboratories where chemical, bac- 

 teriological, and physiological investigations are conducted. In 

 manj^ instances success in the maintenance of cultures depends upon 

 tha ability continuously to maintain practically constant temperature. 

 Pathogenic microorgani'-ms, as a rule, do not grow except within very 

 narrow temperature limits, the optimum temperature being about 

 3T.5° C. (99.0° F.). 



The Bureau of Animal Industry, United States Department of 

 Agriculture. i)r()duces tuberculin on a large scale ; about ICOOO culture 

 flasks of 300 c. c. capacity are maintained to produce the required 

 (juantity. The tubercle bacillus is very sensitive to temperature 

 changes. In order to obtain the best groAvths, therefore, the tempera- 

 ture during the peiiod of incubation should be maintained practically 

 constant at the optiminn of about 37.5° C. To hold the temperature 

 in all jiarts of the chamber approximately constant re(|uii-es con- 

 siderable care, especially if the chamber is lai'ge. 



Other work cai'ried on l)y the bureau includes the study, by 

 bacteriological means, of other diseases of domestic animals. The 



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