Respiration, Aeration, and Fermentation 291 



air. In rough experiments, how- 

 ever, much of the heat is lost by 

 radiation, and such data are merely 

 suggestive. Complex calorimeters 

 are in use to measure the heat of 

 animal respiration, and recently an 

 advance has been made in simple 

 plant experimentation by the use 

 of the doubled-walled silvered 

 Dewar bulbs, or thermal bottles. 

 In preliminary experiments with- 

 out sterilization precautions, Peirce 

 secured a rise of temperature with 

 an unweighed quantity of peas (in 

 a silvered 250 cc. Dewar flask) 

 amounting to about 25 C . in 

 three days, with a maxi- 

 mum rise of about 40 C. 

 reached on the seventh 

 day. With sterilization 

 precautions and employ- 

 ing in 250 cc. silvered 

 Dewar flasks, 300 seeds 

 of Canada field peas, a 

 maximum difference of 

 about 20 C. has been 

 observed in some 

 class tests. 

 This does not 

 represent the 

 actual . differ- 



FIG. 72. Dewar bulb. 



