METHOD FOR MEASURING CARBON DIOXIDE. 113 



to two hours were allowed for absorption of the CC>2 in the above 

 test. 



The applicability of the method to measurement of CO 2 , like 

 some other methods depends upon the assumption that no other 

 volatile acids than CO 2 are excreted by the organisms. 



The carbon dioxide production by Paramecium and various 

 small invertebrates has been measured and the results show that 

 the method is satisfactory. For example in practical tests on 

 Paramecium it was found that twice the number of Paramecia 

 always produced twice the amount of CO2, other conditions being 

 exactly the same in two experiments. When using Paramecium 

 the method is of course brought to a most rigid test of its useful- 

 ness, since the amounts of CC>2 produced by 2 c.c.~4 c.c. of fairly 

 concentrated Paramecium suspension in 8 to 24 hours are much 

 smaller than those produced by an active animal' weighing one 

 gram. Success with the method depends to a considerable 

 extent upon a proper appreciation of the role of the different 

 factors described above and care in manipulation. 



Among what appear to be the special advantages of the method 

 are the following: 



1. It is simple and direct. 



2. Many determinations can be made in a short time when 

 compared with other methods. 



3. The range of adaptibility is considerable and the percentage 

 of error of the method is relatively small when the small amounts 

 of COa which can be measured, is considered. 



4. The apparatus is small and many bottles can be jmmersed 

 in a water bath at the same time, hence temperature can be 

 accurately controlled in many measurements carried out at the 



same time. 



BIBLIOGRAPHY. 

 Thunberg, T. 



'05 Ein Microspirometer. Skand. Arch. f. Physiol., Vol. 17, p. 74. 

 Winterstein, H. 



'13 Ein Microrespiradonsapparat. Zeitschr. f. biol. Technik u. Methodik, 



Vol. 3, p. 246. 

 Krogh, A. 



'16 The Respiratory Exchange of Animals and Man. Monographs on Bio- 

 chemistry. 

 Warburg, O. 



'09 Massanalytische Bestimmung kleiner Kohlensaiiremengen. Zeitschr. f. 

 physiol. Chem., Vol. 61, p. 261. 



