CAPILLAKY RESPIROMETRY 



315 



chambers are bored in a solid brass block, uniform temperature dis- 

 tribution is insured, and thermostasis is required only to control the 

 rate of the reaction to be measured. The apparatus is adapted to 



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(i) 



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Fig. 95. Construction diagram of differential microrespirometer. 

 Lengths are given in inches. 

 From Barth and Kirk (1942) 



measuring gas changes of the order of 0.1-10 /xl. per hour with a read- 

 ing accuracy down to 0.001 /xL, depending on the capillary diameter. 

 In an experiment on the respiration of single pupae of Drosophila 

 nielanogaster the mean deviation from the mean of the six organisms 

 whose oxygen consumption was measured was 4 X 10"^ ju.1. per minute 

 or an average of 2.4%. Barth and Kirk (1942) subsequently simpli- 

 fied the construction of the apparatus and rendered it more adapt- 

 able to multiple determinations; it is this apparatus which will be 

 described (available from Microchemical Specialties Co.) 



Apparatus. A diagram of the Barth-Kirk respirometer is given 

 in Figure 95: The main block {A) is made from a 3 in. length of 

 rectangular brass ( 1^/4 X % in. ). On one narrow face two chambers 



