THE BIOMETER: HOW TO USE IT in 



clear, but when more than a definite amount of carbon 

 dioxide is introduced, a precipitate of carbonate appears, 

 which is detectible by means of a lens. 



3. By the use of accurately known quantities of 

 carbon dioxide of exceedingly high dilution it was found 

 that the minimum amount of carbon dioxide which gives 

 a precipitate is i.oXio" 7 g. 



4. By determining, therefore, the minimum volume 

 of any given sample of the gas necessary to give the 

 first visible formation of the precipitate its carbon 

 dioxide content can be estimated accurately, since this 

 volume must contain just the known detectible amount 

 of the gas, which we found to be i.oXio" 7 g. 



5. By having two chambers side by side the different 

 rates of metabolism from two different tissues can be 

 estimated by the different speeds of formation of the 

 precipitate and extent of the precipitate. 



Description of the apparatus. The biometer shown 

 in Figs, i and 3 is made of glass. It consists of two 

 respiratory chambers connected by a three-way stop- 

 cock Z, the other arm of which is connected to one arm 

 of another three-way stopcock K. (As is shown in 

 Fig. i, for an ordinary experiment we can connect it 

 directly to the nitrometer.) Each of the other two 

 arms of stopcock K is connected to a nitrometer, W or 

 X, which is used for removing the final traces of carbon 

 dioxide from the gas with which the chambers are to 

 be filled. The nitrometer on the right is connected to a 

 carboy F (see Fig. 5, apparatus III), filled with air free 

 from carbon dioxide ; and the other, on the left, to a simi- 

 lar carboy as a reservoir for any other gases that may be 

 used as a special medium for different experiments, such 



