r. We have on the one hand the warm
surface of the man's body, averaging not far from 32 deg. C. On the other
hand we have the cold water in the heat-absorbers at a temperature not
far from 12 deg. C. Obviously, the air in the immediate neighborhood of
these two localities is considerably warmer or colder than the average
temperature of the air. The disposition of the electric-resistance
thermometers about the chamber has, after a great deal of experimenting,
been made such as to permit the measurement as nearly as possible of the
average temperature in the chamber. But this is at best a rough
approximation, and we must rely upon the assumption that while the
temperatures which are actually measured may not be the average
temperature, the fluctuations of the average temperature are parallel to
the fluctuations in the temperatures measured. Since every effort is
made to keep these fluctuations at a minimum, it is seen that the error
of this assumption is not as great as might appear at first sight.
However, the calculation of the residual amount of oxygen in the chamber
is dependent upon this assumption and hence any errors in the assumption
will affect noticeably the calculation of the residual oxygen.

Attempts to compare the determination of the oxygen by the exceedingly
accurate Sonden apparatus with that calculated after determining the
water-vapor and carbon dioxide, temperature and pressure of the air in
the chamber have thus far led to results which indicate one of three
things: (1) that there is not a homogeneous mixture; (2) that during the
time required for making residual analyses, _i. e._, some three or four
minutes, there may be a variation in the oxygen content in the air of
the chamber due to the oxygen continually added from the cylinder; (3)
that the oxygen supplied from the cylinder is not thoroughly mixed with
the air in the chamber until some time has elapsed. That is to say, with
the method now in use it is necessary to fill the tension-equalizer to a
definite pressure immediately at the end of each experimental period.
This is done by admitting oxygen from the cylinder, and obviously this
oxygen was not present in the air when analyzed. A series of experiments
with a somewhat differently arranged system is being planned in which
the oxygen will be admitted to the respiration chamber directly and not
into the tension-equalizer, and at the end of the experiment the
tension-equalizer will be kept at su