t is considered that with a subject having a weight of 70 kilos a
difference in temperature of 1 deg. C. will make a difference in the
measurement of heat of some 60 calories, it is readily seen that the
importance of knowing the exact body-temperature can not be
overestimated; indeed, the whole problem of the comparison of the direct
and indirect calorimetry hinges more or less upon this very point, and
it is strongly to be hoped that ere long the much-needed observations on
body-temperature can be made.

CONTROL EXPERIMENTS WITH THE CALORIMETER.

After providing a suitable apparatus for bringing away the heat
generated inside the chamber and for preventing the loss of heat by
maintaining the walls adiabatic, it is still necessary to demonstrate
the ability of the calorimeter to measure known amounts of heat
accurately. In order to do this we pass a current of electricity of
known voltage through a resistance coil and thus develop heat inside the
respiration chamber. While, undoubtedly, the use of a standard
resistance and potentiometer is the most accurate method for measuring
currents of this nature, thus far we have based our experiments upon the
measurements made with extremely accurate Weston portable voltmeter and
mil-ammeters. Thanks to the kindness of one of our former co-workers,
Mr. S. C. Dinsmore, at present associated with the Weston Electrical
Instrument Company, we have been able to obtain two especially exact
instruments. The mil-ammeter is so adjusted as to give a maximum current
of 1.5 amperes and the voltmeter reads from zero to 150 volts. The
direct current furnished the building is caused to pass through a
variable resistance for adjusting minor variations in voltage and then
through the mil-ammeter into a manganin resistance-coil inside the
chamber, having a resistance of 84.2 ohms. Two leads from the terminals
of the manganin coil connect with the voltmeter outside the chamber, and
hence the drop in potential can be measured very accurately and as
frequently as is desired. The current furnished the building is
remarkably steady, but for the more accurate experiments a small degree
of hand regulation is necessary.

The advantage of the electrical method of controlling the apparatus is
that the measurements can be made very accurately, rapidly, and in short
periods. In making experiments of this nature it is our custom first to
place the resistance-coil in the calorimeter and make the connection