THE BIOMETER: HOW TO USE IT 113 
as oxygen-free air, hydrogen, or volatile anesthetics, and 
which are exposed to an alkaline solution in order that 
every trace of carbon dioxide can be removed from the 
gas in question. As stated before, for ordinary metabo- 
lism experiments we may use but one nitrometer for 
ordinary air only, as shown in the photograph (Fig. 1). 
Chamber A is drawn to a capillary stopcock C; chamber 
Fic. 3.—Biometer. One-third actual size. The shaded portions 
of the apparatus indicate the rubber connection, which is first coated by 
shellac and then sealed with a special sealing wax. Some parts are 
also sealed with mercury. 
B is drawn to a similar capillary stopcock C’, one arm 
of which is connected to another three-way stopcock G, 
one arm of which is connected to a mercury burette T, 
which is used for adjusting the pressure in the apparatus. 
(The slightly different structures should be noted here 
in Figs. 1 and 3, the latter having no capillary stopcock 
C’, but being directly connected with the three-way 
stopcock G. As the latter apparatus requires consider- 
able experience in order to make it perfectly air-tight, 
the former type only, as shown in the photograph, is 
