THE BIOMETER: HOW TO USE IT 129 



will precipitate and the maximum volume which does 

 not give a precipitate for a definite time and weight. In 

 Table I columns 8 and 9 refer to these columns calculated 

 from the experiments for ten minutes' respiration by 

 10 mg. of the nerve. Since we know that the minimum 

 volume which gave a precipitate must contain a definite 

 amount of carbon dioxide, i.e., i.oXio" 7 g., and since 

 we had 15 c.c. of original volume of the respiratory cham- 

 ber, we can calculate the total amount of the gas given 

 off by the sciatic nerve of the frog. 



APPARATUS III 



Although the use of the biometer is perfectly satis- 

 factory for almost all micro-metabolic analyses, and 

 sometimes is indispensable for a quick quantitative com- 

 parison of two different rates of carbon dioxide production 

 from the different tissues, yet it is extremely inconvenient 

 for a complete determination of carbon dioxide pro- 

 duction from a single tissue, the metabolic rate of which 

 is constantly changing and the availability of which is 

 not very great. The necessity for a new device to meet 

 this difficulty was keenly felt when we were studying the 

 metabolic changes before, during, and after the cleavage 

 of a single fish egg. 



The new feature of this special apparatus is a device 

 by which the air after a definite period of respiration by 

 the tissue can be withdrawn into a tube from the respira- 

 tory chamber for subsequent complete analysis. With 

 the new arrangement, therefore, one can make not only a 

 complete analysis with a single tissue, but also several 

 duplicate determinations. 



