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 
io 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., 1.0X1077 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the tissue can be withdrawn into a tube from the respira- 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. 
