A SIMPLE METHOD FOR MEASURING CARBON 

 DIOXIDE PRODUCED BY SMALL ORGANISMS. 1 



E. J. LUND. 



The suitable methods available at the present time for measur- 

 ing the carbon dioxide produced by single cells such as eggs and 

 small organisms weighing not over one or two grams are limited 

 in number and usually only suitable for special types of material. 

 Among the best methods for measuring or comparing small 

 quantities of carbon dioxide produced by small organisms are 

 those by Thunberg ('05) as modified by Winterstein ('13), and 

 Krogh ('16). These are in turn based on the older and well 

 known methods of Pettenkoffer and Petterson. Another method 

 is that used by Warburg ('09) in his studies on sea urchin eggs 

 and a more recent and apparently extremely sensitive method 

 for the detection and estimation of very small quantities of CO2 

 is that of Tashiro ('17). All of these methods may have their 

 own advantages, depending upon the material and the nature of 

 the problem. However, if many separate determinations of 

 CO2 are to be made at the same time, the apparatus must be 

 duplicated or if not, the complexity of the procedure is increased 

 greatly and thus becomes practically impossible. 



In attempting to devise some simple method for measuring at 

 the same time the small amounts of CO 2 produced by separate 

 samples of Paramecium, or small invertebrates weighing one 

 gram or less, the following procedure was adopted. Fig. I and 

 the photograph, Fig. 2, show the arrangement. Two bottles of 

 about two liters capacity, one containing n/ioo HC1 and the 

 other a solution of Ba(OH)a of any concentration between w/75 

 and nfi$o, are provided with soda lime tubes and burettes. 

 The solutions should be made up with CO 2 free distilled water 

 as described in Treadwell and Hall ('15). A bottle of about 

 100 c.c. capacity, has a large glass stopper which fits the bottle 

 very accurately and from which is suspended a small dish by 



1 From the Department of Animal Biology, University of Minnesota. 



105 



