G. H. PARKER 695 



It must be clear from the foregoing account that each apparatus 

 will have its own constant, and that anyone who wishes to calibrate 

 such an apparatus for the absolute amount of carbon dioxide pro- 

 duced will first have to determine this constant by some such method 

 as that already described. Once, however, having made this deter- 

 mination, the formula already given may be used with perfect 

 accuracy for the calculation of the absolute amount of carbon dioxide 

 produced. Since the constant is a measure of the amount of carbon 

 dioxide necessarily present in a given piece of apparatus, in order 

 that a standard change in the indicator shall take place, and since 

 this amount is spread through the space contained within the ap- 

 paratus, it is probable that the constant is directly related to the 

 volume of the apparatus and will be small in an outfit of small 

 volume and large in one of large volume, but such relations have not 

 as yet been worked out. 



BIBLIOGRAPHY. 



Osterhout, W. J. V., A method of studying respiration, /. Gen. Physiol., 191-819, 

 1,17. 



Osterhout, W. J. V., and Haas, A. R. C, A simple method of measuring photo- 

 synthesis, Science, 1918, xlvii, 420. 



